BIOLOGY 11 TEST
Genetics
Total points: 30 All questions are worth 5 points.
1. Hemophilia is a blood disease resulting from a recessive allele on the X chromosome. Women
with two normal X chromosomes are normal. Women who are heterozygous for the hemophilia
allele are carriers. Men with a recessive allele on their X chromosome are hemophiliacs. Imagine
you are a genetic counsellor advising a carrier woman and her normal husband, who are
planning a family. If they have a son, what is the probability that he will be hemophiliac? If they
have a daughter, what is the probability that she will be a carrier? Use a Punnett square to
explain your answer.
2. It is said that “chance has no memory”. Keeping this in mind, what is the probability of a couple
with five daughters having a daughter for their sixth child? What is the probability of a couple
with no children having six sons in a row?
3. In garden peas, tall is dominant to short and axillary flowers are dominant to terminal flowers. If
a cross between two tall plants produces 100 short, axillary flowered offspring out of 1600 total
offspring, what are the genotypes of the parents?
4. Mary Smith, who has blood type A+, sues John Doe for child support, stating that he is the father
of her child. John has Type B+ blood. The child is type 0+. Can John be ruled out as the father?
Why or why not? Use a Punnett square to support your answer.
5. In Drosophila, multiple alleles control eye colour. Wild type (red, allele E1) is dominant to
apricot (E2), which is dominant to honey (E3), which is dominant to white (E4). Use a Punnett
square to show the offspring of a mating between: a) an E1E3 male and an E2E3 female b) an
E2E4 male and an E1E4 female. What are the phenotypic ratios of the offspring from these
crosses?
6. In snapdragons, flower colour shows incomplete dominance. A cross between a red-flowered
(RR) plant and a white-flowered (WW) plant produces pink-flowered offspring. If two pinkflowered plants are crossed and 100 offspring are produced, how many would be red? How
many white? How many pink? Use a Punnett square to explain your answer.