7th Grade PSI - NJCTLcontent.njctl.org/courses/science/7th-grade... · The human cell on the left...

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7th Grade PSI

Inheritance and Variation of Traits

2015-11-02www.njctl.org

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Table of Contents: Inheritance andVariation of Traits

· Mendelian Genetics

· Using Punnett Squares

· Test Crosses

Click on the topic to go to that section

· Genetic Mutations

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Mendelian Genetics

Return to Tableof Contents

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Heredity

Did you ever notice how much children look like their parents and their siblings?

As you can see, it's not only something that happens in humans! This is true about all living things on Earth.

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Frequently Asked Questions

I am sure that questions like these have crossed your mind before:

· Are children ever identical to their parents?

· Why do some people look more like their dad and some look more like their mom?

· How do I get traits from my parents?

· Why are some people born with birth defects or diseases?

These questions (and more) will be answered in this unit!

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Genetics & HeredityHere are two related terms that will show up quite a few times in this section. Try to define them with your table and then pull the tab for the definition:

Genetics

Heredity

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Genetics & HeredityHere are two related terms that will show up quite a few times in this section. Try to define them with your table and then pull the tab for the definition:

Genetics

Heredity

[This object is a pull tab]

Ans

wer

A branch of biology that studies genes, heredity, and variation of

organisms

The passing of traits from parent to offspring (children)

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Review: CellsEarlier this year, we talked about the parts of the cell.

We also talked about mitosis and meiosis and how these processes help organisms live and reproduce.

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Review: MitosisMitosis is the process that helps individual cells reproduce.

In mitosis, one "parent cell" reproduces its DNA and then splits into two identical "daughter cells". The daughter cells are completely identical to the parent cell.

The Stages:

Permission Granted: Jeff Sale - San Diego St Univ

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After meiosis, the pairs of chromosomes split.

This means that each sex cell ends up with 23 individual chromosomes (1/2 of what they started with)!

The human cell on the left has all 23 pairs of chromosomes (one pair is shown).

Click on the cell to see what happens after meiosis!

Review: MeiosisMeiosis occurs in all animals that reproduce sexually (2 parents).In meiosis, the cell splits in two individual sex cells without duplicating its DNA.This means that after meiosis, the sex cells have half of the DNA as a normal body cell.

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1 Where is all of the genetic information (DNA) found in the cell?

A nucleus

B cytoplasm

C cell membrane

D mitochondria

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1 Where is all of the genetic information (DNA) found in the cell?

A nucleus

B cytoplasm

C cell membrane

D mitochondria[This object is a pull tab]

Ans

wer

A

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2 The process of creating new cells from existing cells is called mitosis.

True

False


2 The process of creating new cells from existing cells is called mitosis.

True

False


Ans

wer True

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3 The purpose of mitosis is _______________.

A growth of organisms

B repair of damaged tissue

C both A and B are true

D Neither A nor B are true


3 The purpose of mitosis is _______________.

A growth of organisms

B repair of damaged tissue

C both A and B are true

D Neither A nor B are true


Ans

wer

C

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4 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each daughter cell have after mitosis?

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4 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each daughter cell have after mitosis?


Ans

wer

46 total

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5 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each sex cell have after mitosis?


5 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each sex cell have after mitosis?


Ans

wer

23 total (1/2 of what was originally there!)

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6 Meiosis leads to:

A Four offspring cells

B Genetic Variation

C Cloning

D Both A and B are true

E A, B, and C are true


6 Meiosis leads to:

A Four offspring cells

B Genetic Variation

C Cloning

D Both A and B are true

E A, B, and C are true [This object is a pull tab]

Ans

wer

D

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7 After meiosis, the number of chromosomes is the same in the parent and offspring cells.

True

False

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7 After meiosis, the number of chromosomes is the same in the parent and offspring cells.

True

False


Ans

wer

False. The number of chromosomes in the offspring is 1/2 the parent cell.

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Gregor Mendel

In the 1800s, an Austrian monk named Gregor Mendel conducted a series of experiments that were designed to uncover how traits are passed on from parent to offspring.

His experiments were aimed at addressing one of the most fundamental issues concerning heredity:

What are the basic patterns of heredity?

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1. The “blending” hypothesis : This idea stated that genetic material from the two parents blends together ex: a red flower and a white flower will produce a pink flower

Two Prevailing Original Hypotheses At Mendel's time, there were 2 popular (and incorrect) ideas to explain heredity:

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2. Inheritance of mutations: This idea stated that traits present in parents are modified as they are used or not used, and passed on to their offspring in the modified form.

Two Prevailing Original Hypotheses

ex: A giraffe has a long neck because her parents kept stretching their own necks out to reach the leaves in the trees, and the long neck trait was passed on.

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In order to complete his experiment, Mendel needed to choose an organism that had the following characteristics:

Mendel's Experiments

- Usually small

- Has a short life span - Inexpensive to take care of

- Produce many offspring in a relatively short period of time

- Easy to experiment with

Why do you think these traits would be important to scientists?

Talk about each one at your table and be prepared to share your thoughts.

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Mendel's ExperimentsHow many living things can you think of that fulfill these guidelines? Make a list with the person sitting next to you.

Click below to see what Mendel chose to work with.

The garden pea

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Mendel chose pea plants for his experiment because:

· There are many varieties with distinct traits (such as color).

· He could easily control the matings through cross-pollination.

· Each pea plant has both the male and female reproductive organs.

Mendel's Choice: The Pea Plant

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Mendel chose to track 7 traits (or "observable characteristics") that only came in one of two forms.

The Traits of Pea Plants

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8 Pea plants were particularly a good choice for use in Mendel's experiments for all of the following reasons except that...

A Peas show easily observed variations in a number of characters, such as pea shape and flower color.

B It is possible to completely control matings between different pea plants.

C It is possible to obtain large numbers of offspring from one cross.

D Peas live for an unusually long time.


8 Pea plants were particularly a good choice for use in Mendel's experiments for all of the following reasons except that...

A Peas show easily observed variations in a number of characters, such as pea shape and flower color.

B It is possible to completely control matings between different pea plants.

C It is possible to obtain large numbers of offspring from one cross.

D Peas live for an unusually long time.[This object is a pull tab]

Ans

wer

D

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Experiment #1: Monohybrid Cross

For this experiment, he crossed a purple flower with a white one.

This is called a monohybrid cross because the parent plants differ in only one trait, their flower color.

Results:All of the offspring had purple flowers.

One of Mendel's experiments looked at flower color. A pea plant can either have purple or white flowers.

"mono" = one

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Monohybrid Cross

Mendel then mated two of the purple offspring plants. This cross produced 929 plants.

Results: 705 of the 929 plants had purple flowers and 224 had white flowers

Use a calculator - What percentage of these flowers were purple?

_____________________%

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Monohybrid Cross

Mendel then mated two of the purple offspring plants. This cross produced 929 plants.

Results: 705 of the 929 plants had purple flowers and 224 had white flowers

Use a calculator - What percentage of these flowers were purple?

_____________________%


Ans

wer

75%

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Monohybrid CrossCan you make any conclusions based on these results? Write any ideas below.

Think about the Blending Hypothesis. Does this experiment support or disprove this hypothesis. Why?

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Based on the results from this experiment, Mendel concluded that the trait for white flowers did not disappear in the purple plants, but instead that the purple-color factor was controlling the flower color.

He also concluded that these plants must have carried two factors for the flower-color character: one represented purple and one represented white.

Interpreting Mendel's Results

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9 A genetic cross in which the parents differ in only one trait is known as a ___ cross.

A monohybrid

B dihybrid

C self

D test


9 A genetic cross in which the parents differ in only one trait is known as a ___ cross.

A monohybrid

B dihybrid

C self

D test


Ans

wer

A

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Webquest: Mendel's Peas

This lab will have you try out some of Gregor Mendel's experiments on genetics and heredity.

By the end of this webquest, you will have an idea of the different patterns of inheritance he saw in his experiments.

Click on the picture above to access the website!

http://www2.edc.org/weblabs/mendel/mendel.html

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From Mendel's experiments, he came up with a few ideas that reshaped the study of genetics. His first idea was that genes come in different forms. This causes organisms of the same species to still have some differences.

For example, the pictures above show that the human eye can look a variety of different ways, such as being blue or brown.

Alleles

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Alleles

There is a variation of the gene for flower color in pea plants that can cause it to be purple. Another variation makes it white.

The alternative forms of genes are called alleles.

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The Passing on of Alleles

Looking at his experiments, Mendel also concluded that an organism inherits two alleles (one from each parent) for each trait.

The two alleles may be the same or they may be different.

These alleles will pair up in the child and will determine what the child's physical traits are.

Mother Father

- Represents an allele

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Each allele can be represented with either a capital or lower-case letter.

An organism that has two of the same alleles (i.e two identical letters)for a gene is homozygous for that gene.

Homozygous Organisms

Examples: Two capital letters (AA) Two lowercase letters (aa)

"homo" = the same

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An organism that has two different alleles (i.e two different letters)for a gene is heterozygous for that gene.

Heterozygous Organisms

Example: One capital and one lowercase letter (Aa)

"hetero" = different

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If the two alleles of a pair are different (heterozygous), one allele determines the physical appearance and is called the dominant allele.

The other allele has no noticeable effect on the appearance and is called the recessive allele.

Memory Tactic: The dominant allele dominates the recessive one.

Dominant and Recessive Alleles

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In other words, Mendel came up with the idea that one variation of the trait will be shown.


If one parent has blue eyes and one has brown eyes, the child would more than likely end up with one or the other, as opposed to something like this:

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This hypothesis also went against the "blending hypothesis" from before. How did that hypothesis work?

?

According to Mendel's hypothesis, if the two variations are red and white, then the offspring will either show the red or white trait only.


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Describing TraitsWe can describe a trait in terms of the physical appearance of that trait or the alleles present for a trait.

For example, suppose we are looking at the pea plant below. We can either say that it has purple flowers or that its alleles for the flower color trait are Pp.

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Phenotype vs GenotypeWhen you describe the physical appearance of a trait, you are describing its phenotype.

When you describe the alleles of a trait, you are describing its genotype.

Phenotype: purple flowers

Genotype: Pp

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Phenotype vs GenotypeIn humans, there is a gene for eye color.

The brown eye gene (B) is dominant to the blue eye gene (b).

Suppose that you meet someone who is homozygous dominant for this gene. What is their genotype and phenotype? Click in the boxes to check your answers.

Genotype Phenotype

BB brown eyes

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Mother Father

Law of SegregationA sex cell carries only one allele for each trait because allele pairs separate (or segregate) from each other during meiosis and go into separate cells. This is known as The Law of Segregation.

This means that the parent can't "accidentally" pass on two of the same chromosome.

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10 Alternate versions of a gene are called ___.

A chromatids

B heritable factors

C heterozygotes

D alleles


10 Alternate versions of a gene are called ___.

A chromatids

B heritable factors

C heterozygotes

D alleles


Ans

wer

D

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11 An organism that has two identical alleles for a gene is said to be ___ for that gene.

A dominant

B recessive

C homozygous

D heterozygous


11 An organism that has two identical alleles for a gene is said to be ___ for that gene.

A dominant

B recessive

C homozygous

D heterozygous


Ans

wer

C

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Using Punnett Squares


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We just discussed Mendel's Law of Segregation. Use the space below to explain it in your own words.

The Law of Segregation

Mother Father

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The possible combinations of sperm and egg (the human sex cells) can be shown using a Punnett square.

A Punnett square is a diagram for predicting the results of a genetic cross between two individuals.

Punnett Square

?In order to understand how our Punnett Square will look, we need to figure out how many possible combinations of alleles there can be.

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12 According to Gregor Mendel, how many alleles did an organism have for each trait?


12 According to Gregor Mendel, how many alleles did an organism have for each trait?


Ans

wer

2

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Setting Up a Punnett Square

All organisms have two alleles for each characteristic and passes one of these on to the offspring (remember the Law of Segregation!).

The image on the right demonstratesthis as seen in humans. Fill in the blanks to note the number of chromosomes in the parent and sex cells.

Mother Father

Parent's Cell

____chromosomes

Sex Cells

____ chromosomes

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CombinationsIn order to find out the possible number of combinations, let's picture it in a different situation: clothing.

Below, you see four pieces of clothing. Make as many different combinations of shirts and pants as you can!

BA

Place combinations here.Shirts Pants

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CombinationsOn the page before, we had 2 possible types of shirts (A and B) and 2 possible types of pants (purple and black).

We discovered from our activity that there are 4 possible combinations of these pieces of clothing.

Creating each possible combination is fine when the numbers are small, but what about when this would not be practical?

A A B B

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The Counting PrincipleIf there are A number of options for one object and there are B number of options for a second object, then the total number of combinations of the two is:

A x B

So in our example, there were 2 types of shirts and 2 types of pants. The total number of combinations of shirts and pants will be:

2 x 2 = 4

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13 Mindy is at the ice cream parlor. There are 6 different flavors of ice cream and 4 different types of cones. How many different types of ice cream cones can she make?


13 Mindy is at the ice cream parlor. There are 6 different flavors of ice cream and 4 different types of cones. How many different types of ice cream cones can she make?


Ans

wer

6 x 4 = 24

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14 Steven is making a sandwich. When he opens the refrigerator, he sees 2 different types of breads, 5 different types of meat and 2 different types of cheese.

How many different sandwiches could he make using one type of bread, one meat, and one cheese?


14 Steven is making a sandwich. When he opens the refrigerator, he sees 2 different types of breads, 5 different types of meat and 2 different types of cheese.

How many different sandwiches could he make using one type of bread, one meat, and one cheese?


Ans

wer

2 x 5 x 2 = 20

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Back to the Punnett Square...

Since the mother can pass on 2 alleles and the father can pass on 2 alleles, there are 4 potential combinations. (2 x 2 = 4)

Therefore, our Punnett Square is going to consist of 4 boxes:

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As Mendel said, alleles come in two different forms: dominant or recessive. Mendel represented these different traits with either a capital or a lower-case letter.

An uppercase letter represents a dominant allele, and a lowercase letter represents a recessive allele.

We will be using these letters in our Punnett Square.

A aDominant Recessive

Dominant and Recessive Traits

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Genotype

In order to set up our Punnett Square, we need to know what the parents' genotypes are.

The "genotype" is what the person's genes, or DNA, look like.A person's genotype determines what trait they have and what visible trait you will see!

For our sample Punnett Square, let's give the parents the following genotypes:

MotherAa

FatherAA

Memory Tactic: The "genotype" tells you what the "genes" look like

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Setting Up a Punnett SquareA Punnett Square works like a data table; information will be put on the top of the table and on the left of the table.We will put one parent's genotype on the top (in this case, the mother's) and the genotype of the other parent (the father) will go on the left.

Mother's Genotype

Father's Genotype

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Click on the boxes to uncover the components of the Punnett Square:

Mother's Genotype

Father's Genotype

A a

A

A

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AA Aa

AA Aa

Click on the boxes to uncover the components of the Punnett Square:

Mother's Genotype

Father's Genotype

A a

A

A

The genotypes in the Punnett Square represent the possible combinations that the offspring could have.

The offspring can only be either be AA or Aa.

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15 Two of the four boxes contained "AA." Which term below accurately describes this genotype?

A Homozygous Dominant

B Homozygous Recessive

C Heterozygous

D Heterozygous Dominant

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15 Two of the four boxes contained "AA." Which term below accurately describes this genotype?



C Heterozygous



Ans

wer

A

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16 The other two boxes contained "Aa." Which term below accurately describes this genotype?



C Heterozygous



16 The other two boxes contained "Aa." Which term below accurately describes this genotype?



C Heterozygous



Ans

wer

C

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PhenotypeWe have already learned that "genotype" is what the genes look like.

The "phenotypes" of an organism are the observable characteristics, the organism's physical traits. The phenotypes are based on the genotypes and can be seen very easily.

What are some phenotypes of the man to the left? Make a list with your table.

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Dragon Crossing Activity

In this activity, you will be given the task of breeding a special dragon for the king. Use your knowledge of Punnett Squares, genotypes and phenotypes

to complete the process!

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Mendel's Experiments

A A

a

a

In his experiments, Mendel crossed a homozygous dominant purple flower with a homozygous recessive white flower.

Complete the cross:

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The dominant allele shows in the heterozygous flower, while the recessive allele has no effect on flower color. Therefore, a Aa flower has a purple phenotype (purple is dominant).

AA Aa

Phenotype

Genotype

Heterozygous Genotype

Even though the genotypes are different, What do you notice about the phenotypes?

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On the flip side, if an organism shows the recessive phenotype, there is only one way their genotype could look:

aa

Phenotype

Genotype

Homozygous Recessive Genotype

The organism HAS to have two recessive alleles. If it has even one dominant allele, what phenotype will it show?

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17 In Mendel's experiment three slides back, what colors were the offspring flowers?

A All purple

B All white

C All pink

D 1/2 purple, 1/2 white


17 In Mendel's experiment three slides back, what colors were the offspring flowers?

A All purple

B All white

C All pink

D 1/2 purple, 1/2 white


Ans

wer

A

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The Next GenerationIn the next step of Mendel's experiment, he took 2 of the offspring from his first cross and decided to cross them as well:

Aa x Aa

Set up and complete the cross below:

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18 How many flowers in the 2nd generation were purple?

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18 How many flowers in the 2nd generation were purple?


Ans

wer

3

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19 Three out of four flowers were purple. What percentage of the flowers were purple?


19 Three out of four flowers were purple. What percentage of the flowers were purple?


Ans

wer

75%

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We can see that if both the mother and father pass on an A allele, the offspring will be AA and therefore have purple flowers.

In this type of cross, this particular genotype (homozygous dominant) will statistically occur in about 1/4 of the offspring.

F1 Generation

F2 Generation

A

a

A a

AA

Aa

Aa

aa

Looking at Genotypes

Mother's Genotype

Father's Genotype

AAHomozygous Dominant

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F1 Generation

F2 Generation

AA Aa

Aa aa

There are two ways in which a heterozygous organism can emerge:

Mom passes on A - Dad passes on aMom passes on a - Dad passes on A

What percent of offspring could have the Aa genotype?What color will their flowers be?


Mother's Genotype

Father's Genotype

AaHeterozygous

A

a

A a

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The remaining 1/4 of the plants will likely inherit an a from both the mother and the father.

These plants will have a aa genotype and will be what color?


Mother's Genotype

Father's Genotype

aaHomozygous Recessive

F1 Generation

F2 Generation

A

a

A a

AA

Aa

Aa

aa

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In this example, AA and Aa plants had the same phenotype but different genotypes.

Genotype vs. Phenotype

AA or Aa

Phenotype Genotype

We have already established that the genotype (what the genes look like) determines what the phenotype (the physical traits) will be.

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Genotype Phenotype

Purple

Purple

aa

Complete the chart below for the flowers we have discussed.

Genotype vs. Phenotype

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20 Red flowers (R) are dominant to white flowers. According to the chart below, Parent Plant A has what color flowers?

A Red

B White Parent Plant B RR

Parent Plant A Rr

Flower Genotype


20 Red flowers (R) are dominant to white flowers. According to the chart below, Parent Plant A has what color flowers?

A Red

B White Parent Plant B RR

Parent Plant A Rr

Flower Genotype


Ans

wer

A

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21 Red flowers (R) are dominant to white flowers. According to the chart below, Parent Plant B has what color flowers?

A Red

B White

Parent Plant B RR

Parent Plant A Rr

Flower Genotype


21 Red flowers (R) are dominant to white flowers. According to the chart below, Parent Plant B has what color flowers?

A Red

B White

Parent Plant B RR

Parent Plant A Rr

Flower Genotype


Ans

wer

A

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22 The plants below can produce white flowers.

A True

B False

Parent Plant B RR

Parent Plant A Rr

Flower Genotype

F1 Generation

F2 Generation


22 The plants below can produce white flowers.

A True

B False

Parent Plant B RR

Parent Plant A Rr

Flower Genotype

F1 Generation

F2 Generation


Ans

wer

B

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23 The probability that the Parent Plants A and B will produce a plant with red flowers is ______%.

Parent Plant B RR

Parent Plant A Rr

Flower Genotype

Ans

wer

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Jane and John ActivityHow are traits passed on from parent to offspring?

In this activity, you and a partner will be determining the traits of two individuals and will use a Punnett Square to look at the possible genotypes that their child can have!

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Test Crosses


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How can we tell the genotype of an individual with the dominant phenotype? In Mendel's pea plants those with WW or Ww both appeared purple.

So if we have a pea plant with purple flowers, how do we determine which genotype the plant has?

Determining Genotype from Phenotype

AA ?

Aa ?

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Test CrossA test cross involves breeding the individual whose genotype we are trying to determine with a homozygous recessive individual.

In a test cross, you will always cross an organism that shows the dominant trait with one that shows the recessive trait.

Permission Granted:Penn State Dept of Biology

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Test Cross

In a test cross, the unknown genotype is either homozygous dominant or heterozygous.

What would the offspring look like if the unknown genotype is homozygous dominant? Complete a punnett square to determine your answer. Click below to check your answer.

F1 Generation

F2 Generation

p p

P

P

Pp Pp

Pp Pp

All offspring would show the dominant phenotype.

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Test Cross

What would the offspring look like if the unknown genotype is heterozygous? Complete a punnett square to determine your answer. Click below to check your answer.

F1 Generation

F2 Generation

p p

P

p

Pp Pp

pp pp

Half of the offspring will show the dominant phenotype and half will show the recessive phenotype.

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Test Cross Results

If any offspring displays the recessive phenotype, the parent must be heterozygous (Pp).

If all offspring display the dominant phenotype, the parent must be homozygous dominant (PP).

Permission Granted:Penn State Dept of Biology

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24 An organism's expressed, or physical, traits are known as its:

A genome

B genotype

C phenome

D phenotype


24 An organism's expressed, or physical, traits are known as its:

A genome

B genotype

C phenome

D phenotype


Ans

wer

D

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25 Crossing an individual that is homozygous recessive with an organism of unknown genotype that exhibits a dominant phenotype is known as a ____________.

A hybrid cross.

B heterozygous cross.

C testcross.

D unknown cross.


25 Crossing an individual that is homozygous recessive with an organism of unknown genotype that exhibits a dominant phenotype is known as a ____________.

A hybrid cross.

B heterozygous cross.

C testcross.

D unknown cross.[This object is a pull tab]

Ans

wer

C

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Setting up a Testcross

To complete a testcross, you must always cross one organism with the dominant phenotype with one that shows the recessive trait.

F1 Generation

F2 Generation

p pP = Purplep = white

In order for the one flower to be white,it must have one particular genotype.

This genotype has been added to the Punnett Square to the right.

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Setting up a Testcross

F1 Generation

F2 Generation

p p

P

P = Purplep = white

As for the other flower, we know it must have at least one dominant allele, which has been added to the Punnett Square on the right.

How do we know this must be true?

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Solving a Testcross

F1 Generation

F2 Generation

p p

P

The other letter is being represented by a "?" because we do not know if it is a "P" or a "p" yet.

We need to look at the offspring in order to know what the parent's genotype is. Because of this, we will do two different crosses to see how the offspring will differ.

?

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Solving a Testcross

F1 Generation

F2 Generation

p p

P

?

We can begin filling in the Punnett Square above with the information we have so far:

This will help us see what allele we must fill in for the question mark.

Pp Pp

?p ?p

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F1 Generation

F2 Generation

p p

P

P

F1 Generation

F2 Generation

p p

P

p

PP x pp Pp x pp

__________% purple flowers

__________% white flowers

_____/4 purple flowers

_____/4 white flowers

_____/4 purple flowers

_____/4 white flowers

__________% purple flowers

__________% white flowers

Pp Pp Pp Pp

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Testcross Trends

The percentages on the prior slide hold true for every testcross:

If every offspring shows the dominant trait (100%), the parent with the dominant traitis homozygous dominant (ex. PP).

If about half of the children show dominant and the other half show recessive (50% / 50%), the parent with the dominant trait is heterozygous(ex. Pp).

FYI: If even one child shows the recessive trait, the parent must be heterozygous. The percentages above only represent the probability.

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Testcross ActivityThis activity will allow you to practice setting up and solving testcrosses.

At each station will be a different situation.

Using the file folder and the sticky note papers, you will set up and solve the testcross.

You will then transfer the information to your student worksheet!

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Genetic Mutations


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Review: DNADNA is the blueprint of life.

DNA contains ______________ that carries instructions for making proteins that control an organism's life functions.

DNA is shaped like a ____________.

Each rung of the ladder is made up of compounds. The order of these compounds determines what protein will be made in the cell.

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Review: DNA

DNA can be found in the _____________ of the cell.

It plays a vital role in cellular reproduction (which is called _________) and helping the cell survive.

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Review: Base Pairs

DNA is made up of 4 bases: adenine , thymine , guanine , and cytosine .

We will refer to them as A T C and G.

_____ and _____ always bond together.

_____ and _____ always bond together.

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Review: Protein Synthesis

These bases play a role in protein synthesis .

During protein synthesis, information from DNA is carried to the ribosomes, where it is used to make proteins out of amino acids.

The sequence of genetic information found on the genes determines what kind of protein is made.

For example:

AAG or TCG

Each of the trios above will lead to the creation a different protein.

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The Role of ProteinsProteins have much more significance than we think! They do most of the work in our cells and are the basis for all of the organs and tissues in our bodies.

Proteins are made up of many different subparts known as amino acids . The

sequence of letters in our DNA determines what amino acids are

made.

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The Role of Proteins

The image to the right may look like a blob, but it is actually a protein knownas hemoglobin.

This protein is found in our blood and isresponsible for carrying oxygen from theblood to the rest of the body!

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Types of Proteins

- Antibodies are responsible for getting rid of viruses and bacteria in the body.

- Enzymes carry out all of the chemical reactions inside of cells. They also help form new molecules by reading the DNA.

- Messenger proteins, such as hormones, send signals throughout the body to coordinate different things.

- Some proteins are required for structure and support for cells. They also allow the body to move.

- Finally, some are responsible for transport and storage of atoms and molecules in the body.

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MutationsEvery cell in your body contains a copy of the same exact DNA.Every so often though, a mutation will occur to alter your genetic blueprint.

A T

A

G

T

C

T

C

A

G

A

A

A

A

T

T

T

T

C G

A mutation is a change in the DNA sequence that can reshape your entire genetic code. It could happen as a result of an error in DNA duplication or by the insertion or deletion of genetic code inside the cell.

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Mutations

In the example above, the base pair of G and C was somehow eliminated. This may have happened accidentally through an error during DNA replication or the DNA could have been damaged in some way.

As a result, the genetic code changes. What used to read as AAG and TTC before now reads as AAT paired with TTA after.

This will result in different proteins being made.

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The Domino Effect of Genetic MutationsFor example, read the sentence below:

THE BAD DOG CAN NOT RUN

Now let's remove one piece of this sentence (the "A" in "BAD") and move all of the other letters up in its space:

THE BDD OGC ANN OTR UN

There is a chain effect throughout the rest of the sentence because one piece is missing!

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Environmental Causes of Mutations

There are a few different environmental causes of mutations in human DNA. Some of the most common causes are:

- Radiation (such as UV radiation from the Sun)

- Chemicals (such as coming in contact with radioactive waste)

- Viruses (when viruses attack your cells, they can damage the DNA inside)

Although your body has ways of repairing most accidental changes to your DNA, some errors make their way past these checks and become permanent mutations.

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26 Mutations can happen as a result of exposure to _________.

A sunlight

B radioactive chemicals

C certain viruses

D all of the above


26 Mutations can happen as a result of exposure to _________.

A sunlight

B radioactive chemicals

C certain viruses

D all of the above


Ans

wer

D

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27 Does your body repair all mutations?

Yes

No

(Answer) / 141

27 Does your body repair all mutations?

Yes

No


Ans

wer

No

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28 Changing one letter in the genetic code can cause a mutation.

True

False


28 Changing one letter in the genetic code can cause a mutation.

True

False


Ans

wer

True

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Types of Mutations

Genetic information can be altered through an error in DNA replication or from some sort of environmental damage after the baby is born.

These are called acquired mutations.

If the mutated DNA is present in the sperm or egg cells of an organism, it could then be passed on to the next generation.

A mutation that is acquired from one's parents is called a hereditary mutation. Every cell in this organism's body will have the mutated DNA.

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Are All Mutations Harmful?As was said before, a mutation in one's DNA will alter the proteins that are being coded for in the body. If one or more of these proteins is not functioning properly (or is missing entirely), it can disrupt normal development within the body or can cause a medical condition.

These illnesses are known as genetic disorders .

Progeria Tuberous Sclerosis

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Are All Mutations Harmful?

On the other hand, there are some genetic mutations that have no negative effect on the body at all and some that are even beneficial!

This section will look at a number of possible effects of genetic mutations.

5 ft6 ft 2 in

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Mutations Can be Helpful! Sometimes, DNA mutations can cause an organism to be able to survive better in his or her environment.

For example, imagine that there is an organism with a genetic mutation that makes it immune to cancer. What types of advantages would this creature have over other organisms in its same species?

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29 Mutations can occur in DNA _________.

A only before a baby is born

B anytime during an organisms life

C only when an organism is exposed to something bad

D only when the pregnant mother does something to cause them


29 Mutations can occur in DNA _________.

A only before a baby is born

B anytime during an organisms life

C only when an organism is exposed to something bad

D only when the pregnant mother does something to cause them [This object is a pull

tab]

Ans

wer

B

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30 All mutations are bad.

True

False


30 All mutations are bad.

True

False


Ans

wer

False

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Mutations Can be Helpful!

There are people out there who have genetic mutations that help them live longer, healthier lives. One real-world example comes to us from a small village in Italy called "Limone sul Garda."

Some of the people in this community possess a mutation in a protein in their blood that helps their bodies clean out cholesterol from their veins.

Possessing this trait allows the people to eat whatever they want with little to no risk of heart disease.Out of about 1,000 people in the town, more than a dozen have lived past 100!

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Passing on Beneficial Mutations

Organisms who have a beneficial mutation will oftentimes lead longer, healthier lives. If this is the case, there is a strong possibility that these

living things will give birth to many offspring who also possess this useful trait.

If this is able to continue for many generations, the mutation will become more common and will be viewed as a normal variation of a trait.

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Beneficial Mutations and Natural Selection

Organisms with a beneficial genetic trait

are more likely to survive to pass that trait on to their

offspring.

Natural selection is a gradual process wherein some traits become more

or less common in a population over time.

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Adaptation by Natural Selection

Adaptation by natural selection happens over long periods of time, through many generations. Usually these changes are in response to changes in the environment.

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Distribution of Traits

As the environment changes, organisms will also change. Those traits which help them to survive better and reproduce will become more common in the population.

The traits which hinder reproduction and success will become less common.

Over time, the whole population will change!

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Case Study: Peppered MothsThe peppered moth is a good example of how natural selection can cause different genes to be passed on.

The peppered moth varies in color from light light white/gray to black. The frequency of each color has changed drastically over the past 200 years.

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Case Study: Peppered MothsInitially, the peppered moth population was mostly light colored. The light colored moths were camouflaged against the light colored tree trunks on which they rested. The dark colored moths were not camouflaged and they were eaten by predators.

The light colored moths survived to reproduce and pass on the light colored gene to future generations.

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Case Study: Peppered MothsWith the Industrial Revolution, however, the amount of pollution dramatically increased. The air pollution caused the tree trunks to be stained a darker color.

How do you think this affected the peppered moths? Write your ideas below.

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Case Study: Peppered Moths

Since the tree trunks were now a dark color, the light moths were no longer well camouflaged. They were eaten by predators while the dark moths were able to hide on the tree trunks.

The dark colored moths survived to reproduce and pass on the dark colored gene to future generations.

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Artificial Selection

Humans have the ability to influence certain characteristics by selectively breeding specific traits in animals.

Both of the animals to the right are dogs. How did they become so different?

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By choosing which traits are preferred in plants and animals, humans can choose to breed organisms with those specific traits.

Those characteristics will then be passed on to offspring through the animal's genes.

Why is this called "artificial selection"?

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There

There are many ways humans can influence selection in organisms.

These days, it is easy to select traits using methods such as gene therapy, artificial husbandry (breeding), and even genetic modification.

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31 Animals reproducing on their own in the wild in response to changes to their environment is considered ___________ selection.

A natural

B artificial

(Answer) / 141

31 Animals reproducing on their own in the wild in response to changes to their environment is considered ___________ selection.

A natural

B artificial


Ans

wer

A

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32 Natural selection happens very fast, often in one generation.

True

False


32 Natural selection happens very fast, often in one generation.

True

False


Ans

wer

False

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33 Natural selection causes changes to traits in populations in response to changes in the ____________.

A animal's DNA

B environment

C mutations

D father's DNA only


33 Natural selection causes changes to traits in populations in response to changes in the ____________.

A animal's DNA

B environment

C mutations

D father's DNA only


Ans

wer

B

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Some Mutations Are Neutral

There are some mutations that have no effect, either positive or negative, on our bodies.

Most mutations that occur as a result of a DNA replication error or exposure to radiation is corrected and repaired quickly by the body. Still, there are some that sneak by yet prove to not affect the organisms in a negative way.

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Harmless Mutations

Cats have a number of harmless body mutations that give variety to the species.

Some cats have a mutation that causes their ears to naturally curl.

Other mutations in DNA can cause cats to have a curly tail.

Each of these mutations has a neutral effect on the cat. It neither helps it survive nor hurts it.

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Harmful Genetic Mutations

Harmful genetic mutations can come from an error in DNA replication in the cell, exposure to radiation, or from an error in the passing on of

genetic information from parent to offspring.

Just one incorrect portion of the DNA can cause a change in the

entire chain.

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34 Is the body capable of correcting mutations on its own?

Yes

No


34 Is the body capable of correcting mutations on its own?

Yes

No


Ans

wer

Yes

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Down SyndromeOne relatively common genetic disorder is Down Syndrome.

A normal human baby is born with 23 pairs of chromosomes - one from the mother and one from the father.

What do you notice about the chromosomes to the right which came from a person with Down Syndrome?

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Down SyndromeThis genetic mutation causes significant problems for the child.

Some common characteristics of individuals with Down Syndrome include:

- Shorter height- Weaker muscles- Irregularly shaped mouth, tongue, and teeth- Lower IQ- Heart defects

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Genetic DisordersIt is important to keep in mind that genetic disorders are never the

fault of the individual who must suffer with the ailments.

More often than not, a person who has a certain genetic disorder was born that way and could not help getting the disease. All living

things deserve our respect!

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Genetic Disorders Baby Project

In this wrap-up activity, you will be practicing the skills obtained during this unit and you will also be researching a genetic disorder that you will then teach to the class.

F1 Generation

F2 Generation

A a

A

a

AA Aa

Aa aa

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