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Genetics
b
Q1. Colour blindness is controlled by a gene on the X chromosome. The allele for colour blindness, X , is
B
recessive to the allele for normal colour vision, X . The gene controlling the presence of a white streak in the

hair is not sex linked, with…

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Answer ............................................
(2)
(Total 7 marks)


Q2. The production of pigment in rabbit fur is controlled by two genes.

One gene controls whether any pigment is made. This gene has three alleles. Allele A codes for the production
h
of one form of the enzyme tyrosinase, which converts tyrosine into…

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(2)
(Total 9 marks)

Q3. A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat
produced 8 black kittens and 4 white kittens.

(a) (i) Explain the evidence that the allele for white fur is recessive.

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(1)…

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(iii) The breeder had expected equal numbers of chocolate and cinnamon kittens from the cross
between the chocolate male and black female. Explain why the actual numbers were different
from those expected.

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(1)

(iv) The breeder wanted to produce a population of cats that would all have chocolate…

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Q5.S Redgreen colour blindness is caused by a mutation in the gene coding for one of the opsin proteins which
are needed for colour vision. The diagram shows the inheritance of redgreen colour blindness in one family.










Person 12 is pregnant with her fourth child. What is the probability that…

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(1)

(ii) Suggest one method by which the scientists could collect a random sample of ladybirds from the
trees.

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(1)

Some of the results from the investigation are shown in the table.

Year Season Frequency of b allele

1933 Autumn 0.70

1934 Spring 0.82

1934 Autumn…

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allele. The two genes are inherited independently but the effects of the alleles interact to produce three different
coat colours. The table gives four genotypes and the phenotypes they produce.

Genotype Phenotype

BbEe black

bbEe chocolate

Bbee yellow

bbee yellow



(a) What colour coat would you expect each of the…

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(i) the genotype
bbee produces a yellow coat colour

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(2)

(ii) the genotype BbEe produces a black coat colour.

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(2)
(Total 9 marks)

Q8. Human ABO blood groups are determined by the presence or absence of two antigens (A and B) on the
plasma membrane of…

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(3)
(Total 5 marks)

Q9. (a) (i) Explain what is meant by a
recessive allele.

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(1)

(ii) Explain what is meant by
codominant alleles.

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(b) The Rhesus blood group is genetically controlled. The gene for the Rhesus blood group has two alleles.…

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Show your working.





Answer .....................................................
(3)
(Total 9 marks)


Q10. Duchenne muscular dystrophy is a sexlinked inherited condition which causes degeneration of muscle
tissue. It is caused by a recessive allele. The diagram shows the inheritance of muscular dystrophy in one
family.






(a) Give evidence from the diagram which suggests…

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