We use…

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# We use… - PowerPoint PPT Presentation

So far, we’ve been looking at single traits…but what if Patrick married and wanted to know the probability of having offspring that were pink AND had large eyes? How do we figure this out?. We use…. Dihybrid Punnett Squares. Dihybrid Punnett Squares. Defined : Crossing of two traits

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Presentation Transcript

So far, we’ve been looking at single traits…but what if Patrick married and wanted to know the probability of having offspring that were pink AND had large eyes? How do we figure this out?

We use…

DihybridPunnett Squares

Dihybrid

Punnett

Squares

• Defined: Crossing of two traits
• 16 possible outcomes
• Use the “FOIL” method from math

F = First

O = Outer

I = Inner

L = Last

• Tips:
• Place capital letters first
• 2) Group the same letters together
First, we have to figure out all possible gamete combinations (using that FOIL method).
• For example:

Patrick is heterozygous for his pink body color but is purebred dominant for having large round eyes.

What is the genotype for his body color? Pp

What is the genotype for his round eyes? RR

Together, this is PpRR.

Now, lets figure out the possible gamete combinations

P p R R

So, the possible gamete combinations are:

PR, PR, pR, pR

Now, let’s do the same for Patrick’s new lady, Patti
• For example:

Patti is homozygous recessive for her yellow body, but is heterozygous for her large round eyes.

What is the genotype for her body color? pp

What is the genotype for his round eyes? Rr

Together, this is ppRr.

Now, lets figure out the possible gamete combinations

p p R r

So, the possible gamete combinations are:

pR, pr pR, pr

We put gamete combos on axis and fill in:

PR

PR

pR

pR

PpRR

PpRR

ppRR

ppRR

pR

PpRr

ppRr

ppRr

pr

PpRr

pR

PpRR

PpRR

ppRR

ppRR

PpRr

ppRr

ppRr

pr

PpRr

Ta-Daa!!!! 

Key:

R = Round Y = yellow

r = wrinkled y = green

• Cross two heterozygous dominant Round, Yellow seeds with each other.

R r Y y x R r Y y

RY

Ry

rY

ry

RY

RrYy

RrYY

RRYY

RRYy

Ry

Rryy

RRYy

RRyy

RrYy

rY

RrYY

RrYy

rrYY

rrYy

RrYy

ry

Rryy

rrYy

rryy

R = Round

r = wrinkled

Y = Yellow

y = green

List all the Possible Genotypes:

List all the Possible Phenotypes:

1 RRYY

4 RrYy

1 rrYY

9 Round, Yellow Seeds

2 RRYy

1 RRyy

2 rrYy

3 Round, Green Seeds

2 RrYY

2 Rryy

1 rryy

3 Wrinkled, Yellow

1 Wrinkled, Green

What is the probability of getting:

Competely homozygous recessive seed?

1/16th

Completely heterozygous plants?

4/16th

Homozygous round seeds?

4/16th

What is the probability of getting:

Wrinkled, yellow seeds?

3/16th

Green seeds?

4/16th

Three round, yellow seeds?

9/16 x 9/16 x 9/16 =

729/4096 or 17.8%

Genotypes:

Phenotypes:

1 RRYY

4 RrYy

1 rrYY

9 Round, Yellow Seeds

2 RRYy

1 RRyy

2 rrYy

3 Round, Green Seeds

2 RrYY

2 Rryy

1 rryy

3 Wrinkled, Yellow

1 Wrinkled, Green