# Biology

QUESTION 1

1. Having hair on the back of the hands is a dominant trait. If two people who heterozygous for the condition have children, what is the probability that they will have a child who does NOT have hair on the back of their hands?

0%

25% or 1/4

50% or 2/4

75% or 3/4

100% or 4/4

8.5 points

QUESTION 2

1. Who is responsible for sex determination in humans?

male

female

6.5 points

QUESTION 3

1. In the pedigree below, all shaded individuals express the gene in question. For example, Arlene “has” the trait, she displays the phenotype in question. For example, if we were following the inheritance pattern of a widow’s peak, Arlene has a widow’s peak (that is NOT the trait here, just an example). Unshaded individuals (blank circles and squares) do not manifest the trait in question, but their specific genotype is unknown – they could be heterozygous, homozygous dominant, or homozygous recessive.

2. What is the mechanism of inheritance of this trait?

recessive

dominant

8.5 points

QUESTION 4

1. In the pedigree below, all shaded individuals express the gene in question. For example, Arlene “has” the trait, she displays the phenotype in question. For example, if we were following the inheritance pattern of a widow’s peak, Arlene has a widow’s peak (that is NOT the trait here, just an example). Unshaded individuals (blank circles and squares) do not manifest the trait in question, but their specific genotype is unknown – they could be heterozygous, homozygous dominant, or homozygous recessive.

What is Sam’s genotype?

homozygous recessive (hh)

heterozygous (Hh)

homozygous dominant (HH)

8.5 points

QUESTION 5

1. Normally when a person consumes a product that contains lactose (such as milk or cheese), the body breaks the sugar lactose down into galactose and glucose. Galactosemia is disorder caused by a missing or defective enzyme which ends up causing galactose to accumulate to poisonous and sometimes deadly levels. Galactosemia is a recessive disorder. If two individuals are heterozygous for this trait, what is the probability that their children WILL HAVE galactosemia?

0%

1/4 or 25%

2/4 or 50%

3/4 or 75%

4/4 or 100%

8.5 points

QUESTION 6

1. Huntington’s disease is characterized by a late onset of nerve degeneration that leads to death. The allele that causes the disease is dominant. Lucille is homozygous dominant for the disease and Joe is homozygous recessive. What is the probability that their children will have Huntington’s disease?

0%

1/4 or 25%

2/4 or 50%

3/4 or 75%

4/4 or 100%

8.5 points

QUESTION 7

1. Hemophilia, disease in which the blood lacks a clotting factor, is caused by an X linked recessive gene. Joe doe not have hemophilia and Lucille is heterozygous for the condition. What is the chance that their MALE child will have hemophilia? (Note: you are calculating the probability for their MALE children only, in other words if they have 1 male child, what is the probability that he will be born with the disease?)

0%

1/4 or 25%

2/4 or 50%

3/4 or 75%

4/4 or 100%

8.5 points

QUESTION 8

1. In humans, having facial dimples is dominant to not having facial dimples. Mary has dimples, yet only 3 of her 10 children have dimples. What must Mary’s genotype be?

homozygous dominant

heterozygous

homozygous recessive

has dimples

does not have dimples

8.5 points

QUESTION 9

1. Red-green color blindness is an X-linked recessive disorder. If Allison is heterozygous (a carrier), and her husband, Michael, is NOT colorblind. What is the chance that their male children will be colorblind? (Note: you are calculating the probability for their MALE children only, in other words if they have 1 male child, what is the probability that he will be born with the disease?)

0%

25% or 1/4

50% or 2/4

75% or 4/4

100% or 4/4

8.5 points

QUESTION 10

1. Red-green color blindness is an X-linked recessive disorder. If Allison is heterozygous (a carrier), and her husband, Michael, is NOT colorblind. What is the chance that their female children will be colorblind? (Note: you are calculating the probability for their FEMALE children only, in other words if they have 1 female child, what is the probability that she will be born colorblind?)

0%

25% or 1/4

50% or 2/4

75% or 3/4

100% or 4/4

8.5 points

QUESTION 11

1. Match the term to its best description.

the observable trait expressed by an organism

the genes for a trait present in an organism

the different varieties of a gene for a particular trait

the state of having two identical alleles for a particular trait

A.

homozygous

B.

genotype

C.

phenotype

D.

alleles

QUESTION 12

1. Why do X-linked genetic disorders occur more frequently in males? Answer in a few short sentences.