EOC Prep 5

1. In pea plants, the trait for tall stems is dominant over the trait for short stems. If two  heterozygous tall plants are crossed, what percentage of the offspring would be expected to have the  same phenotype as the parents?

• A. 100% 
• B. 75% 
• C. 50% 
• D. 25% 

2. Hemophilia is a sex-linked, recessive trait. Which of the following describes the probability of  hemophilia in the offspring of a man who does not have hemophilia and a woman whose father is a  hemophiliac?

• A. Each of their sons will have hemophilia.  
• B. None of their daughters will have hemophilia.  
• C. Their sons have a 25% chance of having hemophilia.  
• D. There is a 50% chance that their daughters will have hemophilia. 

3. Alleles for the A and B blood cell antigens are codominant. The condition where no antigens  are present on the blood cells (type O blood) is a recessive trait. Which set of parents can most likely  produce a child with type O blood?

• A. one parent with type AB blood, and the other parent with type A blood 
• B. one parent with type AB blood and the other parent with type O blood 
• C. one parent with heterozygous type A blood, and the other parent with type O blood 
• D. one parent with homozygous type A blood, and the other parent with homozygous type B  blood

4. One of the parents of a child has phenylketonuria (PKU), which is caused by recessive alleles.  The other parent does not have the PKU alleles. What is the chance that the couple will have a child  with phenylketonuria?

• A. 0% 
• B. 50% 
• C. 75% 
• D. 100%

5. Hitchhiker's thumb (H) is dominant to no hitchhiker's thumb (h). A woman who does not have  hitchhiker's thumb marries a man who is heterozygous for hitchhiker's thumb. What is the probable  genotypic ratio of their children?

• A. 0% Hh: 100% hh 
• B. 50% Hh: 50% hh 
• C. 75% Hh: 25% hh 
• D. 100% Hh: 0% hh

6. This diagram shows a pedigree for a recessive genetic disorder. What is the genotype of individual 6?

• A. XHXH 
• B. XHXh 
• C. XHY 
• D. XhY

7. A pair of male Holstein (black-and-white) calves that have the same parents display many  similarities but also exhibit some variations. Which process best explains these variations?

• A. independent assortment 
• B. sex linkage 
• C. dominance 
• D. gene linkage

8. A human baby boy inherits a recessive allele from his mother. In which circumstance would he  most likely show the trait coded for by the recessive allele?

• A. The baby inherits the dominant allele from his father.  
• B. The allele is on an autosomal chromosome and the baby is a twin.  
• C. The allele is on the X chromosome. 
• D. The allele is on the Y chromosome.

9. This diagram shows a diploid cell with two pairs of homologous chromosomes.Due to independent assortment, what is the possible genetic make-up of gametes produced by this  organism?

• A. SsTt 
• B. Ss, Tt 
• C. S, s, T, t 
• D. ST, St, sT, st

10. The table lists the trials for fruit color where allele R exhibits incomplete dominance over allele  R'. Heterozygous fruit have orange phenotypes. What percent of offspring are expected to have  an orange phenotype if the parent plants are orange (RR') and yellow (R'R')?

• A. 25% 
• B. 50% 
• C. 75% 
• D. 100%