Genetics OST Biology

• A
• B
• C
• D

A Only

• A
• B
• C
• D

B Only

• A
• B
• C
• D

The gene that causes Huntington’s Disease is autosomal dominant. Consider one couple where the wife has the disease as did her mother. The husband does not. The children, now that they are 18 years old, are considering taking the blood test to determine if they have the gene for Huntington’s. Many people in their situation have chosen not to take the test. Which of the following is true?

• There is a 50% chance that only a daughter will inherit the disease.
• There is a 50% chance that only a son will inherit the disease.
• It is certain that one of the children has the gene.
• There is a 50% chance that any child of these parents would have the disease.

In one strain of mice, fur color ranges from white to darkest brown with every shade of brown in between. This pattern of inheritance for fur color is most likely controlled by

• Multiple genes
• A single gene with many alleles
• Pleiotropy
• Incomplete Dominance

In guinea pigs, the gene for short hair is dominant, and the gene for long hair is recessive. The gene for black hair color is dominant over the gene for white hair color, which is recessive. A cross between two guinea pigs produces a litter of 9 short-haired black guinea pigs and 3 short haired white guinea pigs. What is the most likely genotype of the parent guinea pigs in this cross?

• SSBB x SSBB
• SSBB x SSBb
• SsBb x SsBb
• SSBb x Ss Bb

A couple has 6 children, all girls. If the mother gives birth to a 7th child, what is the probability that the seventh child will be a girl?

• 6/7
• 1/128
• ½
• 1

A child is born with blood type O. All of the following could be the blood type of the parents EXCEPT

• A and B
• A and A
• O and O
• AB and O

In a certain species of plant, the trait for tall is dominant (T) and the trait for short is recessive (t). The traid for yellow seeds is dominant (Y) and the trait for green seeds is recessive (y). A cross between two plants results in 292 tall yellow plants and 103 short green plants. Which of the following are most likely to be the genotypes of the parents?

• TtYY x Ttyy
• TTYy x TTYy
• TTyy x TTYy
• TtYy x TtYy

A round watermelon is crossed with a long watermelon and all the offspring are oval. If two oval watermelons are crossed, what is the percent of watermelons that will be round?

• 0
• 25%
• 50%
• 75%