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Section 1: Meiosis

Section 2: Mendelian Genetics

Section 3: Gene Linkage and Polyploidy

Chapter 10 Sexual Reproduction

and Genetics

Human body cells have

46 chromosomes

10.1 Meiosis

Sexual Reproduction and Genetics

Each parent contributes

23 chromosomes

Chapter 10

Homologous

chromosomes—one of

two paired

chromosomes, one from

each parent

Chromosomes and Chromosome Number Chromosomes and Chromosome Number

10.1 Meiosis


Same length

Same centromere position

Carry genes that control the same inherited traits

Chapter 10

Haploid and Diploid Cells

Human gametes contain

23 chromosomes.


10.1 Meiosis

An organism produces

gametes to maintain

the same number of

chromosomes from

generation to

generation.

Chapter 10

Haploid and Diploid Cells


A cell with n

chromosomes is called

a haploid cell.

A cell that contains 2n

chromosomes is called

a diploid cell.

10.1 Meiosis

Chapter 10

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Meiosis I

The sexual life cycle

in animals involves

meiosis.


Meiosis produces

gametes.

10.1 Meiosis

When gametes

combine in fertilization, the number of

chromosomes is restored.

Chapter 10

Stages of Meiosis I

Reduces the chromosome

number by half through the

separation of homologous

chromosomes


Involves two consecutive

cell divisions called meiosis

I and meiosis II

10.1 Meiosis

Chapter 10

Meiosis I


10.1 Meiosis

Interphase

Chromosomes replicate.

Chromatin condenses.

Chapter 10

Interphase

Meiosis I


10.1 Meiosis

Prophase I

Pairing of homologous chromosomes occurs.

Each chromosome consists of two chromatids.

The nuclear envelope breaks down.

Spindles form.

Chapter 10

Prophase I

Meiosis I


10.1 Meiosis

Prophase I

Crossing over produces exchange of genetic

information.

Crossing over—chromosomal segments are

exchanged between a pair of homologous

chromosomes.

Chapter 10

Meiosis I


10.1 Meiosis

Metaphase I

Chromosome centromeres attach

to spindle fibers.

Homologous chromosomes line up at the equator.

Chapter 10

Metaphase I

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Meiosis I


10.1 Meiosis

Anaphase I

Chapter 10

Anaphase I

Homologous chromosomes

separate and move

to opposite poles of the cell.

Meiosis I


10.1 Meiosis

Telophase I

The spindles break down.

Chromosomes uncoil and form two nuclei.

The cell divides.

Chapter 10

Telophase I

Meiosis II

Prophase II


10.1 Meiosis

Chapter 10

A second set of phases begins

as the spindle apparatus forms and the chromosomes condense.

Prophase II

Meiosis II

Metaphase II


10.1 Meiosis

Chapter 10

A haploid number of chromosomes

line up at the equator.

Metaphase II

Meiosis II


10.1 Meiosis

Anaphase II

Chapter 10

Anaphase II

The sister chromatids are

pulled apart at the centromere by spindle fibers and move toward the opposite poles

of the cell.


10.1 Meiosis

Meiosis II

Chapter 10

Telophase II

The chromosomes reach the poles, and

the nuclear membrane and nuclei reform.

Telophase II

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Meiosis II


Cytokinesis results in four haploid cells,

each with n number of

chromosomes.

10.1 Meiosis

Visualizing

Meiosis I and Meiosis II

Chapter 10

Cytokinesis

The Importance of Meiosis

Meiosis consists of two sets

of divisions


Produces four haploid

daughter cells that are not

identical

10.1 Meiosis

Results in genetic variation

Mitosis and

Meiosis

Chapter 10


Meiosis Provides Variation

Depending on how the

chromosomes line up at the

equator, four gametes with

four different combinations

of chromosomes can result.

Genetic variation also is

produced during crossing

over and during fertilization,

when gametes randomly

combine.

10.1 Meiosis

Chapter 10 Sexual Reproduction and Genetics

Sexual Reproduction v. Asexual Reproduction

Asexual reproduction

The organism inherits all of its chromosomes from a single parent.

The new individual is genetically identical to its parent.

Sexual reproduction

Beneficial genes multiply faster over time.

10.1 Meiosis

Chapter 10

Gregor Mendel Father of Genetics

Austrian monk who

formulated the basis of modern genetics

1822-1884

1900 his paper

rediscovered

Genetics- The branch

of biology that studies heredity.

Why did Mendel choose pea plants?

1) Many varieties exist.

Easy to distinguish traits.

2) Small, easy to grow

plants that mature quickly

3) Self-pollination

4) Easy to cross

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Pollination

Self Pollination – fertilizing itself

Cross Pollination – breeding between two

flowers

Self Pollination Cross Pollination

Mendel’s Experimental Design Step 1

Ensure True Breeding – allow each variety to self-pollinate

These plants are the parental generation or

P - Generation


Cross pollinate two varieties from the P generation

that had different traits.

The offspring are called the first filial generation or

F1 generation

P

F1


Allow the F1 generation to self pollinate

Offspring are called F2 generation

Mendel counted these plants.

F1

F2

Mendel’s Observations

Classified the trait expressed in the F1 generation the dominant trait.

The trait not expressed in the F1 generation is the recessive trait.

When the F1 generation was allowed to self pollinate, the recessive trait reappeared in some of the F2 plants.

At this point Mendel counted the F2 generation and noticed a 3:1 ratio

F2 Self Pollination Results

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F2 Self Pollination Results

Plants showing recessive traits were true

breeding (all recessive)

Plants showing dominant traits only 1 was

true breeding

The actual ratio is 1:2:1 (1 true dominant: 2

not true dominant: 1 true recessive)

Mendel proposed a Theory of Heredity

1) Parents do not transmit traits directly to

their offspring.

* Genes are passed on to the offspring that

operates in the offspring to produce the

trait.


2) For each trait, an individual has two

alleles,1 from mother and 1 from father.

Allele – copy of a factor, or gene

Homozygous - both genes have the same

information

Heterozygous – genes are different


3) Phenotype: Physical appearance

Genotype: Set of genes that an individual has

4) An individual receives an allele from each parent

5) The presence of an allele does not mean the trait will be expressed in heterozygous individuals, only the dominant allele is expressed.


We can represent an allele by a letter. In

the case of the pea plants let’s assign Y for

the yellow pea gene and y for the green

pea gene.

Y,y are the alleles, the offspring received 1

from each parent.

YY and yy are homozygous

Yy is heterozygous

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Phenotype Genotype

YY Yellow Pea Homozygous Yellow Pea

YY

Yy Yellow Pea Heterozygous Yellow Pea

Yy

yy Green Pea Homozygous Green Pea

yy

Sexual Reproduction and Genetics Chapter 10

Mendel studied seven different traits.


Seed or pea color

Flower color

Seed pod color

Seed shape or texture

Seed pod shape

Stem length

Flower position

10.2 Mendelian Genetics

Chapter 10

Mendel’s Law of Segregation


Two alleles for each trait separate during meiosis.

During fertilization, two alleles for that trait unite.

Heterozygous organisms are called hybrids.


Chapter 10

Monohybrid Cross


A cross that involves hybrids for a single

trait is called a

monohybrid cross.



Dihybrid Cross

The simultaneous inheritance of two or more traits in the same plant is a dihybrid cross.

Dihybrids are heterozygous for both traits.


Chapter 10

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Law of Independent Assortment

Random distribution of alleles occurs during gamete formation

Genes on separate chromosomes sort independently during meiosis.

Each allele combination is equally likely to occur.


Chapter 10

Probability

Probability – The likelihood that a specific event will

occur.

# of one kind of possible outcome

Total # of all possible outcomes

Formula can be used to predict the outcome of a genetic cross.


Punnett Squares

Predict the possible offspring of a cross

between two known

genotypes


Punnett

Squares


Punnett Square—

Dihybrid Cross

Four types of alleles from

the male gametes and

four types of alleles from

the female gametes can

be produced.

The resulting phenotypic

ratio is 9:3:3:1.


Chapter 10

How to build Punnett Square

Monohybrid Heterozygous Example

Rabbits black coat is dominant (B) over brown (b)

Step 1 Figure out the genotype of the parental generation.

Step 2 Draw a table with all possible allele combinations of 1 parent across the top and the other up and down to the left

B

b

Sperm

Egg

Parent’s Genotype

Bb (egg) X Bb (sperm)

B b

How to built Punnett Square

Monohybrid Heterozygous Example


Step 3 Fill in Punnet Square

Step 4 Figure out genotype and phenotype

BB Bb

Bb bb

B

b

Sperm

Egg

B b Genotype

1 BB, 2 Bb, 1 bb

Phenotype

3 black, 1 brown



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You Solve!


Cross a Homozygous black coat rabbit with a

Heterozygous black coat rabbit. (BB X Bb)

BB BB

Bb Bb

B

b

Sperm

Egg

B B

Genotype

2 BB, 2 Bb

Phenotype

All black

How to build Punnett Square

Dihybrid Heterozygous Example

Rabbits S=Short hair s=long hair

B=Black b=brown

Step 1 Figure out the genotype of the parental generation.

Step 2 Draw a table with all possible allele combinations of 1 parent across the top and the other up and down to the right

Parent’s Genotype

SsBb (egg) X SsBb

(sperm)

SB

Sb

sB

sb

SB Sb sB sb

How to built Punnett Square

Dihybrid Heterozygous Example

Guinea Pigs S=Short hair s=long hair

B=Black b=brown

Step 3 Fill in Punnet Square

Step 4 Figure out genotype and phenotype

SSBB SSBb SsBB SsBb

SSBb SSbb SsBb Ssbb

SsBB SsBb ssBB ssBb

SsBb Ssbb ssBb ssbb

SB

Sb

sB

sb

SB Sb sB sb

Genotype

Listed on black board

Phenotype

Listed on black board

You Solve!

Rabbits black coat is dominant (B) over brown (b) and Short hair (S) over long hair (s)

Cross a Heterozygous Short Black hair rabbit with a Homozygous Short Black hair rabbit (SsBb X SSBB)

SSBB SSBB SSBB SSBB

SSBb SSBb SSBb SSBb

SsBB SsBB SsBB SsBB

SsBb SsBb SsBb SsBb

SB

Sb

sB

sb

SB SB SB SB Genotype

4 SSBB, 4 SSBb

4 SsBB, 4 SsBb

Phenotype

All black short haired.

Genetic Recombination

The new combination of genes produced by crossing over and independent assortment

10.3 Gene Linkage and Polyploidy


Combinations of genes due to independent assortment can be calculated using the

formula 2n, where n is the number of

chromosome pairs.

Chapter 10

Gene Linkage

The linkage of genes on a chromosome results

in an exception to Mendel’s law of independent

assortment because linked genes usually do not

segregate independently.



Chapter 10

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Polyploidy


Polyploidy is the occurrence of one or more extra

sets of all

chromosomes

in an organism.

A triploid organism,

for instance, would

be designated 3n,

which means that

it has three complete sets of chromosomes.



Chapter Resource Menu

Chapter Diagnostic Questions

Formative Test Questions

Chapter Assessment Questions

Standardized Test Practice

biologygmh.com

Glencoe Biology Transparencies

Image Bank

Vocabulary

Animation Click on a hyperlink to view the corresponding lesson.

Chapter 10

A. #

B. x

C. r

D. n

Which symbol is used to represent the number of chromosomes in a gamete?


Chapter Diagnostic

Questions

A. Felix Mendelssohn

B. Gregor Mendel

C. Dr. Reginald Punnett

D. Albert Einstein

Name the person known as the father of genetics.


Chapter Diagnostic

Questions

A. gamete

B. hybrid

C. phenotype

D. genotype

Which term refers to the outward expression of an allele pair?


Chapter Diagnostic

Questions

Segments of DNA that control the production of proteins are called _______.


A. chromatids

B. chromosomes

C. genes

D. traits

Chapter 10

10.1 Formative

Questions


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What is the term for a pair of chromosomes

that have the same length, same centromere

position, and carry genes that control the same

traits?


A. diploid

B. heterozygous

C. homozygous

D. homologous

Chapter 10

10.1 Formative

Questions

How does the number of chromosomes in gametes compare with the number of

chromosomes in body cells?


10.1 Formative

Questions


10.1 Formative

Questions

A. Gametes have 1/4 the number of

chromosomes.

B. Gametes have 1/2 the number of

chromosomes.

C. Gametes have the same number of

chromosomes.

D. Gametes have twice as many

chromosomes.

What type of organisms only reproduce asexually?


A. bacteria

B. protists

C. plants

D. simple animals

Chapter 10

10.1 Formative

Questions

What is the name for different forms of a single gene that are passed from generation

to generation?


A. alleles

B. genotypes

C. phenotypes

D. traits

Chapter 10

10.2 Formative

Questions

Which pair of alleles is heterozygous?


A. RR

B. Rr

C. rr

D. yR

Chapter 10

10.2 Formative

Questions

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In rabbits, gray fur (G) is dominant to black

fur (g). If a heterozygous male is crossed with

a heterozygous female, what is the phenotypic

ratio of the possible offspring?


A. 1:1

B. 1:2:1

C. 2:1

D. 3:1

Chapter 10

10.2 Formative

Questions

Which explains how the shuffling of genes

during meiosis results in billions of possible

combinations?


A. crossing over

B. gene linkage

C. genetic recombination

D. independent segregation

Chapter 10

10.3 Formative

Questions

True or False

Two genes on the same chromosome may

become separated during meiosis.


10.3 Formative

Questions

What is the term for an organism that has one

or more sets of extra chromosomes in its cells?


A. diploid

B. gamete

C. hybrid

D. polyploid

Chapter 10

10.3 Formative

Questions

A. 6

B. 12

C. 24

D. 36

How many chromosomes would a cell have

during metaphase I of meiosis if it has 12

chromosomes during interphase?


Chapter Assessment

Questions

A. prophase I

B. interphase

C. anaphase I

D. anaphase II

Which stage of meiosis is illustrated?


Chapter Assessment

Questions

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What is the next step for the chromosomes

illustrated?


Chapter Assessment

Questions

A. Chromosomes replicate.

B. Chromosomes move to opposite poles.

C. Chromosomes uncoil and form two nuclei.

D. Chromosomes line up at the equator.


Chapter Assessment

Questions

What is this process called?


A. fertilization

B. gamete formation

C. inheritance

D. reproduction

Chapter 10

Standardized Test

Practice

Before meiosis I, the sister chromatids of

this chromosome were identical. What

process caused a change in a section of

one chromatid?


A. DNA replication

B. crossing over

C. synapsis

D. telophase

Chapter 10

Standardized Test

Practice

At what stage is the chromosome number

reduced from 2n to n?


A. prophase I

B. metaphase I

C. anaphase I

D. meiosis II

Chapter 10

Standardized Test

Practice

To which step in this process does the law of

segregation apply?


Standardized Test

Practice

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A. grows into plant

B. gamete formation

C. fertilization

D. seed development

Chapter 10

Standardized Test

Practice

For human eye color, brown is dominant and

blue is recessive. If a husband is heterozygous

and his wife has blue eyes, what is the

probability that their child will have blue eyes?


A. 0

B. 1/4

C. 1/2

D. 1

Chapter 10

Standardized Test

Practice


Glencoe Biology Transparencies


Image Bank


Image Bank

gene

homologous

chromosome

gamete

haploid

fertilization

diploid

meiosis

crossing over


Vocabulary

Section 1

D:/Chapter 10/Transparencies/Bellringer/Sexual Reproduction and Genetics 3.pdf



D:/Chapter 10/Transparencies/Concepts/Concepts Chapter 10-4.pdf




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genetics

allele

dominant

recessive

homozygous

heterozygous

genotype

phenotype

law of segregation

hybrid

law of independent

assortment


Vocabulary

Section 2

genetic recombination

polyploidy


Vocabulary

Section 3

Visualizing Meiosis I and Meiosis II

Generations


Animation


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