HUMAN GENETICS

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Exercise 1: genotype to Phenotype

Observations

A. Why was the male chosen to determine the sex of the child?

B. Draw a picture of the compiled traits.

C. If this activity was repeated two or three times would the offspring images change? Explain

your answer.

Exercise 2: Punnett Squares

Questions

Use a Punnett square to solve the following scenarios. You MUST INCLUDE THE PUNNET SQUARE AS PART OF YOUR ANSWER FOR EACH OF THESE PROBLEMS.

A. Dominant: cheek freckles

Recessive: no cheek freckles

(Please note that this trait is more complicated than described in this lab exercise, but for learning purposes, assume that this is correct.)

A man with a heterozygous gene for freckles on his cheeks has a child with a woman who does not have freckles on her cheeks. What is the likelihood that their son will have freckles on his cheeks?

B. Dominant: normal; no cystic fibrosis

Recessive: cystic fibrosis

A woman has a history of cystic fibrosis in her family, and found out that she has the gene for cystic fibrosis, but is not affected by the gene. Her husband also has a history of cystic fibrosis in his family. He got tested yesterday and found that he is also a carrier for the disease, but is not affected by it. They are going to have a baby in two months. What is the likelihood that their baby will have cystic fibrosis?

C. Dominant: normal; no Tay-Sachs

Recessive: Tay-Sachs

A man is a carrier for Tay-Sachs. He is going to have a child with a woman who has homozygous normal genes. What are the chances that they will have a child who has Tay-Sachs disease?

D. Dominant: Round face Dominant: Prominent chin

Recessive: Square face Recessive: Non-prominent chin

(Please note that this trait is more complicated than described in this lab exercise, but for learning purposes, assume that this is correct.)

A woman with heterozygous genes for a round face shape and a chin that is not prominent has a child with a man who has a square face and homozygous genes for a prominent chin. What are the chances that the child has a square face with a prominent chin?

E. Dominant: Huntington’s disease Dominant: normal; no cystic fibrosis

Recessive: normal; no Huntington’s Recessive: cystic fibrosis

A man with Huntington’s disease is also a carrier for cystic fibrosis. His wife has cystic fibrosis but does not have Huntington’s disease. If they have a baby, what is the likelihood that the baby will have both Huntington’s disease and cystic fibrosis?

F. X-linked dominant trait: no color blindness

X-linked recessive trait: color blindness

A color-blind man marries a non-color-blind woman who is not a carrier for color blindness. What are the chances that they will have a son who is also color-blind?

What are the chances that they will have a daughter who is a carrier for color blindness?

Omit pedigrees.