Mendel and Heredity

HEREDITY:

• SC.7.L.16.1 Understand and explain that every organism requires a set of instructions that specifies its traits, that this hereditary information.

• Objective: I can describe what heredity is because I can identify traits and characteristics

What is heredity? • .

• Heredity is the passing of traits from parents to offspring.

• Traits, such as eye color, result from the information stored in the genetic material

What did Gregor Mendel discover about heredity?

• Gregor Mendel was an Austrian monk – in the 1800’s.

He did the first controlled experiments in heredity.

• His research gave scientists a

basic understanding of Genetics – the study of how traits are passed from parents to offspring

• Mendel studied seven characteristics of pea plants

• A characteristic is a feature that has different forms in a population.

• The different forms of a characteristic are called traits.

• The seven different characteristics Mendel studied were:

characteristic traits?

plant height

flower and pod position

seed shape

seed color

pod shape

pod color

flower color

Is flower color a trait or a characteristic?

How did Mendel perform his experiments?

• 1. He started with plants that were true-breeding – plants that

always produce the same trait in their offspring

• Ex/ Purple flowers that always has offspring with purple flowers

• And white flowers that always have offspring with white flowers

• He crossed a purple flowered plant with a white flowered plant

How did Mendel perform his experiments?

• 2. He took the pollen from one plant and put it on the other – cross pollinated

Results: 3. The first generation plants all had purple flowers.

Conclusions: 4. Purple = dominant trait – the one that masks

(covers up) the other White – Recessive trait – the one that seems to disappear

• 5. He crossed 2 of the first generation purple plants.

• The second generation plants had about ¾ purple and ¼ white.

What did Gregor Mendel conclude about heredity?

• After analysing his results, Mendel concluded that 2 factors control each inherited trait.

• Some traits could only be observed if a plant had two of the same factors.

(like white flowers) • A plant with two different factors would show the dominant factor but still

pass on both factors to its offspring.

• Today scientists call the factors that control traits genes • They call the different forms of the gene alleles. Ex: Gene for flower color has 2 alleles purple and white

We will go through the most common traits that people have

On your sheet, record if you have the mentioned trait or not

You may have to ask your neighbor for help

What is heredity?

What is dominant?

What is recessive?

What is an allele

A farmer crosses a true breeding tall pea plant with a true breeding short pea plant. All of the offspring are tall. Explain these results.

If the farmer crosses 2 of the new (1st gneration) tall pea plants – what can he expect his new pea plants to look like

IFC : Write the question and the sentence of your answer choice for the IFC questions

Mendel was studying the trait of seed color in Pea plants. He crossed yellow seeds and green seeds and found all of the offspring were yellow. 1. What are the 2 alleles of this trait? 2. Which allele was dominant? Why? 3. Which was recessive? Why?

How are traits inherited?

• Mendel’s ideas can be even further explained by our modern understanding of DNA

Genes are segments of DNA found in

chromosomes They give instructions for producing a

certain characteristic Alleles – the different forms of a gene • Each offspring gets one allele from

each parent

R R

A a

• Dominant alleles - shown with CAPTITAL letter

• recessive alleles shown with same lowercase letter.

How do we use symbols in Genetics?

A a

h h

R R

• Heterozygous - An organism with one dominant and one recessive allele for a gene is for that gene – (sometimes called hybrid)

homozygous - An organism with two of the same alleles is for that gene. (can be either 2 recessive alleles or 2 dominant alleles Example: _________ is heterozygous ________ and ________ are homozygous

A a

h h

R R

Purple flowers are dominant and white flowers are recessive

For flower color, if P is for purple, what would we use for white flowers?

What color is this flower?

PP

Pp

pp

How do genes determine traits?

.

Genotype

• GENES

• The combination of alleles

that you inherited from your

parent

• Heterozygous or Homozygous

• Ex: Pp or PP or pp

Phenotype

•PYSICAL FEATURES

•Observable Trait

• Ex: Purple or white

Homozygous red

Green

1 allele for Purple flowers and 1 allele for white

Tall plant

Blonde hair

Heterozygous

Short

What does it mean when we say genotype determines phenotype?

• Summary: The genes you inherit from your parents determine your traits

• Your Genotype determines your phenotype

• HW: Phenotype genotype ws