1. INTERACTIVE MULTIPLE CHOICE QUESTIONS
Genetics
The answers are provided. Explanations of why the alternatives are unsatisfactory are also offered

2. (a) to see if there is a better answer and
These multiple choice questions are similar to the ones set by the GCSE and IGCSE Examination Boards except that, in some cases, there may be more than one acceptable answer
For this reason, even if you select a correct answer at your first attempt, it is worth looking at all the alternatives
(a) to see if there is a better answer and
(b) to see why some of the alternatives are unacceptable

3. Question 1 A father’s blood group is AB; the mother’s is O.
Which of the following blood groups could appear in their offspring?
(a) A
(b) B
(c) AB
(d) O
Question 2

4. Yes The father’s genome must be iAiB The mother’s genome will be iOiO
The combination iAiO is possible and will be expressed as group A because iA is the dominant allele

5. Yes The father’s genome must be iAiB The mother’s genome will be iOiO
The combination iBiO is possible and will be expressed as group B because iB is the dominant allele

6. No The father’s genome must be iAiB The mother’s genome will be iOiO
The offspring will all inherit either iA or iB from their father and iO from their mother. Their genomes will be either iAiO (expressed as group A) or iBiO (expressed as Group B. Group AB is not possible

7. No The father’s genome must be iAiB The mother’s genome will be iOiO
The offspring will all inherit either iA or iB from their father and iO from their mother. Their genomes will be either iAiO or iBiO. The alleles iA and iB are both dominant to iO so group O is not possible

8. Question 2
A pure-breeding male black mouse is mated with a female brown mouse and they produce a litter of 12. The allele for black fur is dominant to the allele to brown fur.
What is the expected distribution of colour and sex in their litter?
(a) 6 brown females and 6 black males
(b) 9 black and 3 brown, all male
(c) 6 black males and 6 black females
(d) 12 black males
Question 3

9. No
The pure-breeding male’s genome must be BB and the brown mouse’s genome must be bb. The allele for black fur is dominant over the brown allele. Therefore all the offspring will be black (Bb)
gametes
Black male
Brown female B B b Bb Bb b bB bB

10. No
As explained in the previous slide, the allele for black fur is dominant to the brown allele, so there can be no brown mice in the litter from this cross
Black male
Brown female B b Bb bB
gametes

11. Yes
Inheritance of colour is explained in the first answer. The male mouse carries the X and Y chromosomes. The female mouse carries two X chromosomes. At meiosis, only one of each chromosome pair goes to the gametes.
gametes
Black male
Brown female BX BY bX
BbXX
BbXY bX
bBXX
bBXY

12. No
Certainly all 12 mice will be black as explained in the first answer, but the sex is inherited as explained in the third answer, so the expectation is that there will be 6 males and 6 females in the litter

13. Question 3
A male heterozygous black mouse (Bb) is mated with a female heterozygous black mouse (Bb) and the litter consists of 12 pups. B is the allele for the black colour. The allele for brown colour is b. The dominant allele is B Which of these ratios is closest to the expected ratio for the distribution of colour among the offspring?
(a) All black X
(b) 6 black and 6 brown
(c) 4 black and eight brown
(d) 8 black and 4 brown
Question 4

14. Not very close
From the Punned square you can see that the expected ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes B b BB Bb B b Bb bb
These are only the chance combinations. It would be possible to produce 12 black pups, since ‘black’ is the dominant allele but this is not close to the expected ratio

15. Not very close
From the Punnett square you can see that the expected ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes B b B BB Bb b Bb bb
These are only the chance combinations. It would be possible to produce 6 black and 6 brown pups but this is not very close to the expected ratio of 9:3

16. Close but …
From the Punnett square you can see that the expected ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes B b B BB Bb b Bb bb
These are only the chance combinations A combination of 4 black to 8 brown is close to the expected ratio of 3:9 but since black is the dominant allele it seems to be the wrong way round

17. The closest
From the Punnett square you can see that the expected ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes B b B BB Bb b Bb bb
These are only the chance combinations A combination of 8 black to 4 brown is closest to the expected ratio of 9:3

18. Question 4
The diagrams represent stages in cell division by mitosis. (only one chromosome is represented). What is the correct sequence of events? a d
(a) a b c d e b
(b) b a c e d e
(c) b a d c e c
(d) d b a c e
Question 5

19. No
The chromosomes shorten and thicken (b) after they have appeared in the nucleus (b). Similarly at the end of cell division, the chromosomes extend and become less visible (d) after the cell divides (e)

20. Yes
This is the correct sequence

21. No
The cell does not start to divide (d) until the chromatids have separated (c). Also, cell constriction (e) precedes cell division (d)

22. No
Cell division (d) does not take place until the chromatids have appeared (b) and separated (c). Also, cell constriction (e) precedes cell division (d)

23. Question 5 The process of cell division by meiosis takes place only…
(a) in skin cells
(b) in red bone marrow
(c) in reproductive organs
(d) in lymphocytes
Question 6

24. No
Although the cells in the basal layer of skin divide rapidly, it is by mitosis

25. No
Cells in the red bone marrow divide rapidly to produce red and white blood cells, but this is by mitosis

26. Yes
The cells in the reproductive organs which produce gametes will undergo a meiotic division and produce haploid gametes

27. No
The lymphocytes are capable of dividing rapidly to produce clones of cells but this involves only mitosis

28. Question 6
In a DNA molecule, which of the molecules listed below pairs with adenine?
(a) thymine
(b) guanine
(c) valine
(d) cytosine
Question 7

29. Yes
thymine
adenine

30. No
Guanine pairs with cytosine
guanine
cytosine

31. No
Valine is an amino acid and not an organic base

32. No
Cytosine pairs with guanine
cytosine
guanine

33. Question 7
If L is the allele for long hair and l is the allele for short hair, B is the allele for black hair and b is the allele for white hair, S is the allele for straight hair and s is the allele for curly hair
What will be the phenotype for a small dog with the genotype LLBbss?
(a) Long, white, straight fur
(b) Short, black, straight fur
(c) Long, white, curly fur
(d) Long, black, curly fur
Question 8

34. No
The allele for black fur is dominant to the allele for white fur

35. No
The dog carries both dominant alleles for long hair

36. No
The dog is heterozygous for the colour gene, but the allele for black fur is dominant to the allele for white fur

37. Yes
The dog is homozygous recessive for the curly allele, homozygous dominant for hair length and heterozygous for the colour gene but the black allele is dominant

38. Question 8
Bacteria can be genetically modified to produce human insulin. The steps involve …
(a) cutting out the insulin gene from human DNA with restriction enzymes,
(b) extracting plasmids from the bacterium,
(c) returning the modified plasmid to the bacterium,
(d) inserting the insulin gene into the plasmid,
(e) cutting open the plasmid with the same restriction enzyme
Which of the following is the correct sequence?
(1) e, b, d, a, c
(3) b, e, a, d, c
Question 9
(2) b, c, e, a, d
(4) b, d, e, a, c

39. No
The plasmids cannot be cut open (e) until they are extracted from the bacterium (b)

40. No
The insulin gene must be inserted in the plasmid (d) before it is returned to the bacterium (c)

41. Yes This is the correct sequence
b, a, e, d, c would also be acceptable because the restriction enzyme can cut the plasmid DNA and human DNA in any order

42. No
The plasmid DNA must be opened (e) before the insulin gene can be inserted (d)

43. Question 9
Before natural selection can take place in an animal, there has to be either …
(a) a gene mutation or
(b) a change of habitat or
(c) a gene recombination or
(d) a climate change
Question 10

44. Yes
A gene mutation which caused a change in the organism could be subject to natural selection

45. No
A change of habitat might favour a variation resulting from a genetic change, such as a mutation, but selection could not result from an organism simply changing its habitat

46. Yes
A new combination of genes could produce a variation that had a selective advantage

47. No
A climate change might favour some variants in a population but could not, itself, produce those variants. There has to be a genetic change for the climate change to act upon

48. Question 10 Which of the following can be inherited?
(a) Cystic fibrosis
(b) AIDS
(c) Sickle cell disease
(d) Tuberculosis

49. Yes
Cystic fibrosis is caused by a gene mutation. The gene controls the movement of salts and water into and out of the cells. The mutated form of the gene causes thick mucus to be secreted by the lungs, airways and pancreas, plus many other symptoms The mutated gene is recessive to the normal gene..

50. No
AIDS is caused by a virus, the human immunodeficiency virus (HIV). The virus is transmitted by sexual intercourse or by infected syringe needles.
An infected mother may pass the disease on to her baby, so the disease may, superficially, appear to be inherited

51. Yes
Sickle cell anaemia is caused by a mutation in a gene controlling the composition of haemoglobin. This mutation causes the red cells to become distorted in low oxygen concentrations and so block small blood vessels The mutated gene is recessive to the normal gene

52. No
Tuberculosis is an infectious disease caused by a bacterium Mycobacterium tuberculosis. The bacteria are carried in the air In most cases, the disease affects the lungs.

53. End of questions
Back to start
End show