Heredity

The passing of traits from parents to offspring

The traits you have resemble your parents

These traits can include ◦ Eye color◦ Shape of Eyes◦ Color of your hair◦ Height

Gregor Mendel

Mendel: Austrian Monk, Father of Genetics

Genetics- branch of biology focusing on heredity

Crossed pea plants, counted offspring , analyzed data

Why are pea plants useful for genetics?

1. Traits exist in 2 opposing forms, without intermediates

2. Have male and female organs Easily control mating (self- fertilization or

cross-pollination)

3. Small, grow easily and quickly, produce many offspring

Monohybrid Cross

Monohybrid Cross: Involves one pair of contrasting traits

For Example: ◦ Crossing a plant with purple flowers

and a plant with white flowers

True Breeding

Step 1: Mendel wanted to create a “Parental generation” also called the “P” generation

True Breeding: Self pollinated pea plants so all the offspring would display only one form of the trait

Ex: A purple flowering plant only produces purple flowers

Why would this be important?

Mendel’s Study of Traits – Step 2

F1 Generation

Step 2: Cross pollinated two P generation plants (Purple and White flowers)

Called the offspring from the P generation the F1 generation (First)

Results: All were purple flowers

F2 Generation

Step 3: The F1 Generation self pollinated.

The offspring from the F1 generation was called the F2 generation

Results: Three purple flowers, one white flower

What were the results of the F1 Generation?

What were the results of the F2 generation?

What should Mendel’s conclusion be?

Give one reason why pea plants are good subjects for genetic experiments

Why was it important that Mendel performed true breeding for the P generation?

What did Mendal call each generation?

Mendel’s Hypotheses

1. Individuals inherit 2 copies of each gene (trait)- one from each parent◦ Gametes carry only one allele for

each inherited trait 2. Alleles- different

contrasting versions of each gene (one from each parent)

Ex: Brown eyes vs. Blue eyes

Mendel’s Hypotheses

3. When 2 different alleles are present the Dominant one is expressed

4. Recessive- trait that’s not expressed when the dominant allele is present

Genetics Terms

In the following gentoype which letter represents the dominate gene?

Which letter represents the recessive gene?

Genetics Terms

Homozygous- 2 alleles of a gene are the same

(PP or pp) Heterozygous- if the 2 alleles

for a gene are different (Pp)◦ Only the dominant allele is

expressed (masks the recessive allele)

Genetics Terms

Genotype- allele combinations (genes)◦ Ff- Heterozygous◦ FF- Homozygous dominant◦ ff- Homozygous recessive

Phenotype: is the physical appearance of the trait

Ex: If “B” equals brown eyes and the genotype is Bb the phenotype (expressed trait) would be Brown eyes

Whiteboards – Quick Questions

What would be the genotype for an individual heterozygous for the “F” trait? Ff

What would be the phenotype for an individual whose genotype is Tt where T is tall and t is short? Tall

Whiteboards – Quick Questions

Give an example of a heterozygous trait Ex: Ff

Give an example of a homozygous trait Ex: FF, ff

What would be the genotype for an individual heterozygous for the “F” trait? Ff

What would be the phenotype for an individual whose genotype is Tt where T is tall and t is short? Tall

Laws of Heredity

Law of segregation

1. Law of Segregation: Allele’s separate during meiosis to produce gametes

F1 generation (zygote) has allele’s for each trait by both parents

Law of Independent Assortment

2. Law of Independent Assortment: Alleles of genes separate independently of one another during gamete formation

Ex: Alleles for plant height separate independently of the alleles for flower color

Results: The inheritance of one trait does not influence the inheritance of another – COMPLETELY SEPARATE

What is the Law of Segregation?

What is the Law of Independent Assortment?

Identify the phenotypes of rabbits with the genotypes Bb and bb, where B- black coat and b- brown coat.