1. A man and his wife are both carriers of the recessive allele causing Tay-Sachs disease (chromosome 15). If they have a
normal child, what is the probability that the child is a carrier of Tay Sachs? A) 1 B) 2/3 C) 1/2 D) 1/3
2. Enamel hypoplasia is an autosomal dominant disorder that results in holes and cracks around the crowns of baby teeth.
Some individuals are apparently unaffected but transmit the trait to their offspring. Individuals with the trait also vary in
the number of teeth affected. This trait is an example of: A) a phenocopy. B) pleiotropy and incomplete penetrance.
C) variable expressivity and incomplete penetrance. D) mitochondrial inheritance.
3. A man and a woman are both carriers for two autosomal recessive disorders, PKU (chromosome 12) and cystic fibrosis
(chromosome 7). If they have a daughter, what is the probability that she will have PKU but not CF? A) 3/4 B) 9/
16 C) 3/16 D) 1/2
4. A man with a recessive deafness allele on chromosome 17 marries a woman who also has a recessive deafness allele, but
on chromosome 3. The probability that their children will be deaf is closest to: A) 100%. B) 50%. C) 25%. D)
0%.
5. The alleles that control which blood group antigens appear on the surfaces of red blood cells are: A) incompletely
dominant. B) variably expressed. C) codominant. D) semidominant.
6. Some people with polydactyly have more than 5 fingers, while others do not. This is an example of a phenotype that is:
A) codominant. B) incompletely dominant. C) incompletely penetrant. D) pleiotropic.
7. Can a woman with blood type A have a child with blood type O with a man who is AB? A) Yes, because of
codominance between the IA and IB alleles. B) No, because a man with type AB blood could not contribute an i allele.
C) Yes, because of epistasis between the I and the H genes. D) No, because the child's genotype must be ii.
8. In a human pedigree that traces the inheritance of sickle cell disease, a filled square represents a: A) male with the
disease. B) female with the disease. C) heterozygous male. D) heterozygous female.
9. An Amish couple (both normal) have four children. The first three children are normal and the fourth child was born with
autosomal recessive disorder known as Ellis-van Creveld syndrome (EvC). EvC was once referred to as 'six-fingered
dwarfism' and is caused by a defective gene on chromosome 4. What is the probability that their next child will have Ellis-
van Creveld syndrome? A) 0 B) 1/4 C) 3/4 D) 1
10. A man and his wife are both carriers of the recessive allele causing Tay-Sachs disease (chromosome 15). If they have a
normal child, what is the probability that the child is a carrier of Tay Sachs? A) 1 B) 2/3 C) 1/2 D) 1/3
11. The genotypic ratio expected from a dihybrid cross is: A) 3:1. B) 1:2:1. C) 9:3:1. D) 9:3:3:1.
12. The second generation resulting from a genetic cross is the ___ generation. A) P1 B) P2 C) F1 D) F2
13. A test for alpha fetoprotein in a pregnant woman's blood can reveal: A) if the woman will miscarry. B) the age of a
fetus. C) whether the embryo's neural tube has closed. D) if the embryo's reproductive system is developing.
14. A structure containing enzymes that enable a sperm cell to penetrate an oocyte's membrane: A) acrosome. B)
midpiece. C) tails. D) heads.
