Big Punnett-ing

Catalyst: Six fingers (S) is dominant over five fingers (s). What is the phenotype of a person who is heterozygous?

How did Mr. LY decide to use the letters “S” and “s” to represent dominant and recessive, above?

Write in complete sentences!

Don’t talk during the Catalyst!

Objectives

By the end of today, SWBAT…

Create and analyze Punnett Squares

Agenda

Catalyst Review Making Babies Lab (GASP!) Punnett Squares Guided Practice Independent Practice Closing

Remember…

GENotype = Combination of alleles inherited from the parents (the GENes)

PHenotype = PHysical expression of the trait

Before we get started, remember… CAPTIALIZED letters are DOMINANT lowercase letters are recessiveExamples: B = brown hair (DOMINANT)b = blonde hair (recessive)Y = yellow (DOMINANT)y = green (recessive) P = purple (DOMINANT)p = white (recessive)

Before we get started…

D = dimples

d = no dimples

D = dimples

d = no dimples

Homozygous dominant

Genotype: DD

Phenotype: have dimples

Homozygous dominant

Genotype: DD

Phenotype: have dimples

Homozygous recessive

Genotype: dd

Phenotype: no dimples

Homozygous recessive

Genotype: dd

Phenotype: no dimples

Heterozygous recessive

Genotype: Dd

Phenotype: have dimples

Heterozygous recessive

Genotype: Dd

Phenotype: have dimples

Before we get started…

B = brown eyes

b = blue eyes

B = brown eyes

b = blue eyes

Homozygous dominant

Genotype: BB

Phenotype: brown eyes

Homozygous dominant

Genotype: BB

Phenotype: brown eyes

Homozygous recessive

Genotype: bb

Phenotype: blue eyes

Homozygous recessive

Genotype: bb

Phenotype: blue eyes

Heterozygous recessive

Genotype: Bb

Phenotype: brown eyes

Heterozygous recessive

Genotype: Bb

Phenotype: brown eyes

Today, you are going to have 20 kids.

What?Yes. In 15 minutes, you will have 20 kids.

You will need to find someone in the class to mate with.

We will demonstrate how this works.

Making Babies Lab!

Each partner has one lunch bag. Each lunch bag represents the genes that person gives to their child.

Inside the bag are the two alleles for ONE gene.

To make a baby… WITHOUT looking into the bag, reach in and

grab a letter (your partner will do the same). Record the genotype in the table below. YOU HAVE JUST MADE A BABY.

Key Point #1

Punnett Squares are diagrams that are used to predict the genotypes of offspring.

Probability…not EXACT

It is important to note that Punnett Squares only give probabilities for genotypes

They don’t give you the EXACT outcomes

Big Pun-nett

Let’s make our own. First things first, draw yourself box and split it into 4 squares.

Punnett like its Hot

Read the problem and find the parents’ genotypes.

Remember to use the first letter of the dominant trait.

A homozygous dominant brown eyed male mates with a heterozygous female.

BB

Bb

Punnett Squares are COOL

Parents go on the top and on the left (keep each parents’ alleles together)

It doesn’t matter which parents goes on the top or the left B B

B

b

Punnett Square Dance

Now, bring them together. The four boxes represent the possible

kids.B B

B

b

BB BB

Bb Bb

Just Punnett!

Now, we analyze. Use quarters to figure out percentages.

B B

B

b

BB BB

Bb Bb

•How many homozygous dominant do we have? 50%

•How many heterozygous do we have? 50%

•How many homozygous recessive do we have? 0%

Punnett baby one more time Lastly, figure out percentages by

phenotypes.

B B

B

b

BB BB

Bb Bb

•What percentage will have brown eyes? 100%

•What percentage will have blue eyes? 0%

Let’s do one more on the board A heterozygous dimpled male mates

with a heterozygous dimpled female.

Whiteboard Guided Practice: Seed Shape

Solve the following Punnett Square.

A homozygous dominant round seeded plant is crossed with a heterozygous wrinkled plant.

Find the genotype and phenotype probabilities.R = round

r = wrinkled

RrRr

RRRRR

R

r

R

Guided Practice: Earlobes

Solve the following Punnett Square

A male with attached earlobes mates with a heterozygous female.

Find the genotype

and phenotype percentages.

F = free

f = attached

ffFf

ffFff

F

f

f

Oh, how we love Spongebob! Mr. LY will now pass out the

“Punnett Squares – Spongebob Style” worksheet

We’ll do some of them together… then you get to try the rest on your own!

Exit Question

Create a Punnett Square for two parents who are heterozygous.

List the percent of children that will have each genotype AND

each phenotype.

Create a Punnett Square for two parents who are heterozygous.

List the percent of children that will have each genotype AND

each phenotype.

D = dimples, d = no dimplesD = dimples, d = no dimples