Do Now

1.Identify the heterozygous and homozygous alleles from below.

1.Aa BB Bb Tt tt Kk Ll GG Oo ZZ

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Bean Genes LabPunnett Squares

Agenda

Please be careful not to make a mess!

Bean Gene Lab

Please be careful not to make a mess!

Punnett Squares

Punnett Square

Why?Way of predicting the likelihood (probability) of offspring carrying certain genetic traits!

What do we need to know?

1. Genotype of parents

2. Which allele is dominant

Purebred = Homozygous

Purebred: Both alleles are for the same trait

Example:FF

Hybrid = Heterozygous

Hybrid = The alleles are mixed; they are for different traits

Example:Ff

Quick Check: Homozygous = stand up, Heterozygous = sit down

BB Homozygous

Bb Heterozygous

bb Homozygous

bB Heterozygous

Remember, capital letters are dominant!

Let’s try another Punnett Square!

Hair Color in HumansB = brown = dominantb = blonde = recessive

Let’s say Kevin Federline and Britney Spears are having a baby…

KFed is heterozygous for brown hair, so….

His genotype is

Bb B

b

And Britney is homogenous for blonde hair, so….

Her genotype is

bb

b b

Bb Bb

bb bb

B

b

b b

Bb Bb

bb bb

Genotype Ratio Percentage Phenotype Ratio Percentage

Bb 2/4

2/4 50%50%

Brown Hair

2/450%

bb Blonde Hair

2/4

50%

The likelihood that an offspring will have Brown Hair is ______________ .

The probability that an offspring will have Blonde Hair is ____________ .

***Important***

Probability is the likelihood something will happen, or the chance that something will happen.

If there is a 25% chance that your kids will have blue eyes, it does not mean that if you have 4 kids one of them is definitely going to have blue eyes!

Widow’s Peak

A recessive gene

W = Normal Hairline

w = Widow’s Peak

Let’s say you have two parents who are heterozygous for the gene

1. What are the chances that their offspring will have a widow’s peak?

2. What are the chances that their offspring will not have a widow’s peak but will carry an allele for a widow’s peak?

3. What are the chances that their offspring will not have a widow’s peak and will not carry a gene for a widow’s peak?

What are their genotypes?

Ww and Ww

Let’s see what happens if the parents have the following genotypes: Ww and ww

1. What are the chances that their offspring will have a widow’s peak?

2. What are the chances that their offspring will not have a widow’s peak but will carry an allele for a widow’s peak?

3. What are the chances that their offspring will not have a widow’s peak and will not carry a gene for a widow’s peak?