Genetics Review

1. Distinguish between genotype and phenotype.

2. Distinguish between homozygous and heterozygous.

3. Distinguish between dominant and recessive.

4. Given the alleles A and a, which is dominant? Which is recessive?

5. Which phenotype, dominant or recessive, can have more than one genotype? Explain.

6. Is it possible to be heterozygous for a trait and show the recessive phenotype? Explain.

7. How would you determine if a green-podded pea plant were homozygous?

8. What is a test cross? Why does one use it? Explain the two possible outcomes and what it tells you.

9. A flower grower is looking for new varieties of petunias. He crosses a yellow flower plant with a blue one and gets green flowered plants. Explain how this is possible.

10. What principle states that the inheritance of one characteristic does not affect the inheritance of another?

11. A mother has two alleles for a given trait. How many does she give to an offspring? What principle describes this?

12. Plants grown by vegetative propagation (i.e., cuttings) have exactly the same traits as the parent plants. Plants grown from seeds may vary from the parent plants in many ways. Explain.

13. Does the height of a pea plant affect the color of its flowers? Why or why not?

14. In a monohybrid cross between homozygous dominant and homozygous recessive parents, there are 32 offspring in the F₂ generation. How many of the offspring would you expect to show the recessive trait?

15. How many genes control a "trait"?

16. Construct a Punnett square for the cross between two plants heterozygous for seed color and seed shape. Determine how many of each phenotype will be present among 16 offspring.

17. One gene has alleles E and e; another gene has alleles F and f. For each of the following genotypes, determine the gametes that will be produced.
a) EEFF      (b) Eeff      (c) eeff       (d) EeFf

18. Of all the chromosomes in one of your cells, half came from each of your parents. About what percentage came from each of your grandparents? Your great-grandparents?

19. Would a skin cell mutation on your hand affect your offspring? Explain.

20. A couple has three sons and one daughter. What is the probability that a fifth child will be female? Explain your answer.

21. Explain the inheritance of human ABO blood groups.

22. What are two genotypes that produce blood type A?

23. Why is there no ABO blood type?

24. What are polygenetic traits? Give an example of a trait controlled by polygenic inheritance.

25. Explain what is meant by the term multiple alleles.

26. Mary has blood type A and she marries John , whose blood type is B. They have three children: Joan. James and Pete. Joan has blood type O, James has blood type A, and Pete has blood type B. Explain how this is possible.

27. A woman having blood type A marries a man with blood type B. They have five children. Two sons have blood type O . One daughter has type AB; another daughter, type A ; a third, type B . Give the genotypes of all individuals.

28. If a man who has type O blood marries a woman who is heterozygous for type B blood, what is the probability of them having a child with B type blood? Type O blood?

29. Mr. and Mrs. Doe had a child named Flo at the same time Mr. and Mrs. Roe had their son Joe. The Roes took Joe home, and after looking at him they claimed that Joe was not their child. They were going to sue the Hospital for the mix up. The Hospital took the blood types of all six individuals to try and prove there was no mix up. The results of the tests were as follows: Mr. Roe had A blood type; Mrs. Roe had A blood type; Joe had O blood type; Mr. Doe had O blood type; Mrs. Doe had AB blood type and Flo had A blood type. Was there a mix up? Explain.

30. Is it possible for two parents with type B blood to produce offspring who are not type B? Explain.

31. Why are there more males with sex-linked problems than females?

32. Roan is a name for cattle that show a heterozygous incomplete dominant genotype. A roan calf's parents were a white cow and a red bull. What is a roan's genotype? Can two roans mate and produce all roans ? Explain.

33. What does it mean if we say genes are linked? Which of Mendel's "laws" do linked genes violate?

34. Explain linkage and show how crossover frequencies are used to make chromosome maps.

35. Discuss sex-linked inheritance in terms of X and y chromosomes.

36. Explain why probability is a useful genetic tool.

37. Explain why a large sample is more statistically reliable than a small sample?

38. Expectant parents want to know if the fetus the woman is carrying has sickle cell disease. Could a genetic counsellor determine this by looking at a karyotype? Explain.

39. In sheep, white coat is dominant. Black is recessive. Occasionally, a black sheep appears in a flock. Black wool is worthless. How could a farmer eliminate the genes for black coat from the flock?

40. In a certain animal, a breed is known that always has a hairy tail; another breed is known that always has a naked tail. How would you determine which trait is dominant?

41. In Canada, it is illegal to marry your immediate relatives. Using the principles of genetics, explain why inbreeding in humans is discouraged.

42. In humans, which parent determines the gender of the offspring? Explain.

43. While examining a population of fruit flies, you notice that a certain trait never appears in males. How can you account for this?

44. Define the term carrier female.

45. Explain why are there more males with sex-linked problems than females?