Reviewing Punnett Squares

Reviewing Punnett Squares

​Another Example of Reading Punnett Square

​Key:

T: tall allele

t: short allele

Is a tool used to predict the possible genotypes for offspring of two known parents​

Punnett Square

Multiple Choice

What is the tool called that is used to predict the probability of a genetic trait?

• Punnett Circle

• Punzel Square

• Square punsell

• Punnett Square

Multiple Choice

Which is an example of a heterozygous genotype?

• Ab

• Bb

• cc

• PP

Multiple Choice

Which of the following is homozygous recessive?

• AA

• Bb

• cc

• AC

Multiple Choice

Which of the following represents homozygous dominate?

• AA

• bb

• Cc

• AC

​Next 2 slides walk you through setting up the Punnett Square

​Step 1: Place genotypes for parents on the outside of Punnett square.

• one parent on left

• other parent on top

• 1 letter above or next to each square

​After alleles are on the outside of the box:

1. Drop the letters on top into the boxes in the same column below it.

2. Move the letters on the side into each square to the right of it (row)

3. If heterozygous, then make sure your upper case letter comes first.

4. When complete you should have 2 letters in each box.

​How to read a Punnett Square

Key​

B: Dominant allele for BLACK

b: Recessive allele for BROWN

***Each box represents 25%***

​Genotype (state the combination of letters in each square):

Bb 100% or 4:0 ratio

​Phenotype (what do the letter combinations represent?)

Heterozygous Black 100% or 4:0 ratio Black to Brown

​Another example of reading Punnett Squares

(pay attention to the ratio differences)

​Key​

T: Dominant allele for TALL

t: Recessive allele for SHORT

​​Genotype (state the combination of letters in each square):

TT: 25%

Tt: 50%

tt: 25%

Ratio: 1:2:1 tall to short

​​Phenotype (what do the letter combinations represent?)

75% Tall

25% short

Ratio: 3:1 tall to short

Multiple Choice

Which is a characteristic that can be passed on to its offspring through its genes?

• Dominant

• Allele

• Gene

• Trait

Multiple Choice

Which of the following is a physical appearance (words describing what you see)

• Genotype

• Beanotype

• Phenotype

• Zimotype

​Vocab needed for following slides about dogs

• Purebred dog: only 1 type Huskey, Pitt Bull, Chow, Hound, Dalmation, Lab, Poodle, etc

• Hybrid and/or Mutt: 2 or more types of dogs mixed together.

Practical Examples

​If a dog is Purebred (DD), the offspring will always look like the dominant dog.

​Purebred : Purebred

DD : DD

Genotype: 100% DD

​Phenotype: 100% purebred

​Purebred : Mutt

DD : dd

​Genotype: 100% Dd

Phenotype: 100% Purebred (hetero)

​Purebred : Hybrid

DD : Dd

​Genotype:

50% DD; 50% Dd

Phenotype:

50% purebred

50% Hybrid

(hetero. purebred)

Multiple Choice

If breeding a purebred (homozygous dominant) 50% if the offfsprings will have the dominant trait.

• True

• False

• No way to know

​More with dogs.....

​Hybrid : Hybrid

​Genotypes:

DD: 25%, Dd: 50%, dd: 25%

​Hybrid : mutt

​Genotypes:

Dd 50%, dd 50%

​FUN FACT: if you have puppies with recessive jeans then you know both parents were not purebred.

​On next slide you are going to create a Punnett Square using Rr and rr. Following slide you will define the genotype and pheno type with percentages.

Draw

You Try Punnett Square: Using Rr & rr

Multiple Choice

Which of the following is the genotypes from the Punnett Square you created?

• RR 50%

  rr 50%

• Rr 50%

  rr 50%

• RR: 25%

  Rr: 50%

  rr: 25%

• RR: 50%

  rr: 50%

Multiple Choice

Looking at the Punnett Square, which box will contain hh?

• 1

• 2

• 3

• Can't determine

Multiple Choice

Using the Punnett Square, which statement is TRUE

• Box 4 is recessive

• Boxes 1 & 3 are heterozygous

• Box 2 is dominate

• Can't determine

Multiple Choice

What percentage will be yellow?

• 25%

• 50%

• 75%

• 100%

Multiple Choice

If B is the allele for BLACK fur, and b is the allele for WHITE fur, what percentage will be BLACK?

• 25%

• 50%

• 75%

• 100%

Multiple Choice

In this cross, what is the ratio of BB to Bb?

• 3:1

• 4:1

• 2:2

• 0:4

Multiple Choice

What is the ratio for homozygous dominant?

• 1:4

• 2:4

• 3:4

• 4:4

Poll

How comfortable are you with punnett squares?

• I do not know anything and need more practice

• I know how to set up top and side of square

• I know how to fill in all the squares

• I know how to interpret the results of the squares