Punnett Square REVIEW

· 5 Steps to Solve Every Punnett Square Problem!

· Having a Widow’s peak is dominant to not having a widow’s peak. Chris is homozygous and has a widow’s peak. Pam is heterozygous for a widow’s peak. What is the probability that they will have a kid who has a widow’s peak?

1. Dominant or Recessive?

2. What are my three options?

1.

2.

3.

3. What are the parents’ genotypes? Use clues in the question to figure it out! YOU HAVE 3 OPTIONS.

4. Fill in the Punnett Square!5. Answer the question! What phenotype does the question ask about?

TRY IT! Hector owns a spotted dog (d). The allele for spots is recessive to the allele for no spots. If his heterozygous dog mates with a homozygous spotted dog, what are the chances they will make a puppy that is NOT spotted?

1. Dominant or Recessive?3. What are the parents’ genotypes?

Mom – Dad –

2. What are my three options? 4.

1.

2.

3.

5. Answer:

1.

2.

3.

4. Two parents with a history of sickle cell disease (a disease that leads to sickle shaped red blood cells that can clog arteries) in their families are concerned about their chances of having a baby with sickle cell disease. Sickle cell disease is a recessive disease (s). The mom and dad are both heterozygous for sickle cell disease. What are the chances (percent) that they will have a kid with sickle cell disease?

NAME:

DATE:

PERIOD:

a.

b. 0%

c. 25%

d. 50%

e. 100%

5.

PEDIGREES REVIEW

Take a look at the pedigree!

1. Are there a lot of people with the disease?

YES dominant

NO recessive

REMEMBER, carriers do NOT have the disease!

2. Is it sex-linked?

· Are there A LOT more males affected (with the disease) than females?

YES SEX-LINKED

NO AUTOSOMAL

1.

2. Using the pedigree to the RIGHT, what mode of inheritance does this genetic disorder follow?

0. Autosomal recessive

0. Sex-linked recessive

0. Autosomal dominant

0. Sex-linked dominant

3.

4.

5.