Transcript 3.2 Punnett Squares

FIRST FIVE!
HW!
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?

Copy the following chart on a new sheet of paper:
TRIAL # BABY’S
GENOTYPE
HETEROZYGOUS OR
HOMOZYGOUS?
1.

Number down to 20.
BABY’S PHENOTYPE
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
 EQ

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 recessive
Examples:
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
Homozygous
dominant
Homozygous
recessive
Heterozygous
recessive
Genotype: DD
Genotype: dd
Genotype: Dd
Phenotype:
have dimples
Phenotype: no
dimples
Phenotype:
have dimples
Before we get started…
B = brown eyes
b = blue eyes
Homozygous
dominant
Homozygous
recessive
Heterozygous
recessive
Genotype: BB
Genotype: bb
Genotype: Bb
Phenotype:
brown eyes
Phenotype:
blue eyes
Phenotype:
brown eyes
Today, you are going to have 20 kids.

In 10 minutes, you will have 20 kids.
Trait: Eye Color
Alleles: B = Brown eyes, b = blue eyes
TRIAL # BABY’S
GENOTYPE
1.
HETEROZYGOUS OR
HOMOZYGOUS?
BABY’S PHENOTYPE
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.
Answer the following questions: (6 minutes)
1. Which phenotype is
dominant? Which is
recessive?
3.
2. Out of 20 trials, how many
times did you get
 BB?
 Bb?
 bb?
(Write it as a fraction. Convert to percent.)
(Write it as a fraction. Convert to percent.)
Out of 20 trials, how many
times did you get babies with
 brown eyes?
 blue eyes?
4. Based on these findings,
what is the genotype and
phenotype of the mother?
The father? EXPLAIN how
you know. Use complete
sentences!
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


Parent generation = P1
Offspring = 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.
BB
A homozygous dominant brown eyed male mates
with a heterozygous female.
Bb
Punnett Squares are COOL

Step 2, Part 2: Parents go on the top and on the
left (keep each parents’ alleles together)
B
B
b
B
Punnett Square Dance


Step 3: Now, bring them together.
The four boxes represent the possible kids.
B
B
B
BB
BB
b
Bb
Bb
Just Punnett!

Step 4: Now, we analyze percent of each
genotype.
B
B
•How many homozygous dominant?
•50%
B
BB
BB
b
Bb
Bb
•How many heterozygous?
•50%
•How many homozygous recessive?
•0%
Punnett baby one more time

Step 5: Figure out percentages by phenotypes.
B
•What percentage will
have brown eyes?
B
B
BB
BB
b
Bb
Bb
•100%
•What percentage will
have blue eyes?
•0%
Help me out here…

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.



Homozygous dominant
Homozygous recessive
Heterozygous
5) % of each phenotype.


Dominant phenotype
Recessive phenotype
Whiteboard Guided Practice: Seed Shape

R
R
R
RR
RR
r
Rr
Rr


R = round
r = wrinkled
Solve the following
Punnett Square:
A homozygous
dominant round
seeded plant is
crossed with a
heterozygous wrinkled
plant.
Find the genotype and
phenotype
probabilities.
A homozygous dominant round seeded plant is
crossed with a heterozygous wrinkled plant.
R
r
R
R
RR
RR
Rr
Rr
GENOTYPES
 Homozygous Dominant (RR)
 Homozygous Recessive (rr)
 Heterozygous (Rr)
PHENOTYPES
 Round seed
 Wrinkled seed
R = round
r = wrinkled
Guided Practice: Earlobes

F
f
f
Ff
ff
f
Ff
ff


F = free
f = attached
Solve the following
Punnett Square:
A male with attached
earlobes mates with a
heterozygous female.
Find the genotype and
phenotype
percentages.
A male with attached earlobes
mates with a heterozygous female.
f
f
F
f
Ff
ff
Ff
ff
F = free
f = attached
GENOTYPES
 Homozygous Dominant (FF)
 Homozygous Recessive (ff)
 Heterozygous (Ff)
PHENOTYPES
 Free earlobes
 Attached earlobes
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
D = dimples, d = no dimples
Create a Punnett Square
for two parents who are
heterozygous.
List the percent of
children that will have
each genotype AND
each phenotype.