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 I decide to use the letters “S” and “s” to represent dominant and recessive?

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.

Oh, Lawd! In 15 minutes, you will have 20 kids.

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

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 Data Table 1. 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

Key Point #2

We refer to the parent generation as P1 and the offspring of that generation as F1.

P1

F1

Big Pun-nett

Let’s make our own. Step 1: Draw yourself a box and split it

into 4 squares.

Punnett like its Hot

Step 2, Part 1: Read the problem and find the parents’ genotypes.

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

Step 2, Part 2: 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

Step 3: Now, bring them together. The four boxes represent the possible

kids.B B

B

b

BB BB

Bb Bb

Just Punnett!

Step 4: Now, we analyze percent of each genotype.

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 Step 5: 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 mate one more time…

A heterozygous dimpled male mates with a heterozygous dimpled female.

1) Draw your box.

2) Find parents’ genotypes. Label box.

3) Bring them together.

4) % of each genotype.

5) % of each phenotype.

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

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

GENOTYPES Homozygous

Dominant (RR) Homozygous

Recessive (rr) Heterozygous (Rr)

PHENOTYPES Round seed Wrinkled seedR = 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

A male with attached earlobes mates with a heterozygous female.

GENOTYPES Homozygous

Dominant (FF) Homozygous

Recessive (ff) Heterozygous (Ff)

PHENOTYPES Free earlobes Attached earlobes

ffFf

ffFff

F

f

f

F = free

f = attached

Oh, how we love Spongebob! 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