Questions about Genetics

1. In guinea pigs there is a gene that codes for hair length. Short hair (S) is dominant to long hair (s). Another gene codes for curly hair. Curly (C) is dominant to straight (c). If a guinea pig has the genotype SsCc, what gametes could it produce?


          a. Ss and Cc 

          b. SC, Sc, sC, and sc 

          c. S, s, C, and c 

          d. SS, CC, ss, and cc

2. If you cross 2 SsCc parents from the last question, how many youngsters would have long, straight hair?


          a. 9/16 

          b. 8/16 

          c. 3/16 

          d. 1/16

















3. The gene for red-green color vision is on the X chromosome. Color-blindness is caused by a recessive allele. A normal woman (XNXN) marries a color-blind man (XnY). What fraction of their children will be color-blind?


          a. 0/4 

          b. 1/4 

          c. 2/4 

          d. 3/4






4. In a small rodent species the genotype CBCB codes for black fur, the genotype CWCW codes for white fur, and the genotype CBCW codes for gray fur. This is an example of ___________.


          a. pleiotropy 

          b. codominance 

          c. incomplete dominance 

          d. a sex-linked trait

5. If you cross a black rodent and a white rodent from the last question what type of youngsters could be produced?


          a. all will be gray 

          b. ½ will be white and ½ will be black 

          c. 1/4 will be black, ½ will be gray, and 1/4 will be white

          d. all will be black





6. If you see the genotype Dd you know that this individual ____________________.


          a. is heterozygous for this trait 

          b. displays both the recessive and dominant traits

          c. is homozygous recessive for this trait

          d. is homozygous dominant for this trait

7. In a testcross an individual of unknown genotype is crossed with ________ .


          a. a homozygous dominant individual 

          b. a homozygous recessive individual

          c. a heterozygous individual 

          d. an individual lacking the gene

8. Which of these is the best description of a dominant allele?


          a. It is the allele that is expressed. 

          b. It is the most common allele.

          c. It is the best allele. 

          d. both b and c

19. A couple gets married and decides to have 3 children. What is the probability that all three will be girls?


          a. 3 x ½ 

          b. ½ x ½ x ½ 

          c. ½ 

          d. 1/4 x 1/4 x 1/4

10. Tall (T) is dominant to short (t) and yellow flower (Y) is dominant to white (y). If you cross a TtYy individual with a TtYy individual what proportion of the offspring will be tall with yellow flowers? (You don’t need a Punnett square to answer this)


          a. 0/16 

          b. 1/16 

          c. 3/16 

          d. 9/16

11. If an allele has multiple effects it is _____________.


          a. a polygene 

          b. codominant 

          c. pleiotropic 

          d. an autosome

12. If a man with type AB blood marries a woman with type O blood, what proportion of their children will have type A blood? (Make sure you write the alleles correctly)


          a. none 

          b. 1/4 

          c. ½ 

          d. all






13. In humans eye color is determined by several genes and eye color can vary from very light blue to very dark brown. This is an example of a trait coded for by ________.


          a. pleiotropic genes 

          b. polygenes 

          c. codominant genes 

          d. incomplete dominance