Section B: Short Answer Questions

1) Explain the relationship between DNA, genes and chromosomes:

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2 Marks

2) A brown animal is crossed with a white one. All the offspring are brown. What does this

suggest about the gene for brown colour in this organism?

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1 Mark

3) In the eye colour of vinegar flies, the trait for red eye colour (R) is dominant over the trait for

white eye colour (r).

(a) What colour are the eyes of a fly with the genotype Rr?

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(b) What are one or more possible combinations of alleles for eye colour in the zygote of a

white-eyed vinegar fly?

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1 + 1 = 2 Marks

4) Mendel discovered that in pea plants the green pea pod is dominant over the yellow pea pod.

a Using G to represent the allele for green pods, and g to represent the allele for yellow

pods, write the genotypes for:

i a homozygous plant with yellow pods: ____________________________

ii a heterozygous plant with green pods: ____________________________

b Complete the Punnett square to represent the cross of two plants heterozygous for pod

colour and state the resulting genotype and phenotype ratios.

Genotypic ratio:____________________________

Phenotypic ratio: ____________________________

1 + 1 + 1 + 1 + 1 = 5 Marks

5) The pedigree below shows the inheritance of a recessive disease caused by the allele (g). Those

with the allele that codes for the dominant trait (G) do not show the disease.

a What is the genotype of an individual:

i with the disease: _________

ii heterozygous: __________

iii without the disease:_______

b What are the genotypes of each of the

following individuals?

i generation I female:________

ii generation II-2:___________

iii affected generation III female:____

iv generation II-3:___________

c Explain how you arrived at your answer in question b, part iv, above:

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3 + 4 + 2 = 9 Marks

6) In terms of chromosomes, what is the difference between a male and a female?

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1 Mark

7) The diagram at right shows the stages

occurring during a cell division.

a) State the name of this type of cell

division: _____________________

b) Suggest one type of cell that might undergo the type of cell division shown:

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2 Marks

Section C: Extended Analysis

Write answers in the spaces provided.

1) The genetic disorder cystic fibrosis is caused by a gene on chromosome number seven. The

disease is recessive. Construct a punnet square in the space below and calculate the percentage

probability of the possible outcomes. Show your calculations.

(a) one parent has the disease and the other parent is not a sufferer or carrier of the disease

(b) neither parent has the disease but both parents are carriers of the disease

(c) neither parent suffers from the disease and one parent is a carrier?

3 + 1 + 1 + 1 = 6 Marks

2) Haemophilia is an X-linked recessive disease. The symbols used to show the relevant genes are

XH for the normal allele on the X chromosome, and Xh for the recessive allele on the X

chromosome.

a State the possible genotypes of a:

i haemophiliac male: _______________________________________

ii non-haemophiliac male:____________________________________

iii haemophiliac female: __________________________________

b A female may be a ‘carrier’ of the disease.

i What is meant by the term ‘carrier’?

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ii What is the genotype of a ‘carrier’ of Haemophilia?

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5 Marks

3) Read the following article from ‘www.goldenrice.org’

a Briefly describe how the rice has been genetically engineered, being sure to mention four facts

mentioned in the article about this process.

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4 Marks

b In your own words, state the concerns that this organisation has for the health of poorer people

and what it has suggested as a solution.

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3 marks

c Not all of the scientific community is supportive of such gene technologies. Details of the rice

were first published in the year 2000 however it is not currently available for human

consumption. Outline a potential benefit and a potential risk of this type of gene technology.

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2 marks