LGS AS Level Biology [Mark Scheme: Inherited Change ] 1/5
Biology 9700 / A2 MS : Inherited Change Marks : 40
Name: ……………………………………………………...... School: .........................
Q1 Fig. 1.1 shows the results of an animal cell that has undergone meiosis I.
Fig. 1.1
(a) State which stage of meiosis II is shown.
Metaphase; [1]
(b) Describe the next stage of meiosis II.
Centromeres divide / splits; R break
Chromatid separate;
Idea movement to opposite poles/Centrioles;
By microtubule / spindle fibres;
Idea mechanism of movement ; [3 max]
LGS AS Level Biology [Mark Scheme: Inherited Change ] 2/5
(c) Describe what has happened before the start of meiosis to
(i) the nuclear membrane;
Breaks down / disperses; [1]
(ii) the centrioles.
Centriole divides / replicate ;
To form two pairs (of centrioles);
Move to (opposite) poles; [2]
(d) Name and explain two ways in which meiosis can lead to variation.
1 random alignment / independent assortment / or description;
Different mix of maternal and paternal chromosome / chromatids;
2 crossing over / chiasmata formation / exchange of genetic material ;
Between chromatids of homologous chromosomes;
Break up linkage groups / mix maternal and paternal alleles ;
In 1 or 2 ref. different gametes produced ; [max 4]
[Total : 11]
Q2 Pure-breeding pea plants with round, yellow seeds were crossed with pure-breeding pea plants with
wrinkled, green seeds. The offspring all had round, yellow seeds. These seeds were grown and the
resultant plants allowed to self-pollinate.
This produced 1112 offspring with the following characteristics.
630 round, yellow seeds
202 round, green seeds
216 wrinkled, yellow seeds
64 wrinkled, green seeds
(a) Using the symbols R for round, r for wrinkled, B for yellow and b for green, draw a genetic
diagram to explain these results.
[4]
LGS AS Level Biology [Mark Scheme: Inherited Change ] 3/5
(b) Explain why the wrinkled, green seeds produced pure-breeding offspring, while the round,
yellow seeds did not.
(c) A ratio of 9:3:3:1 was expected.
A chi-squared test was carried out to test the significance of the differences between the
observed and expected results. This gave a value of 0.47.
With reference to the table of probabilities, explain how the value for the chi-squared test
supports the hypothesis that these are two pairs of segregating alleles at two loci.
[Total : 9]
Q3 (a) Distinguish between phenotype and genotype.
phenotype is the feature/characteristic;
results from interaction of genotype and environment on organism
/environment may alter the appearance of an organism;
genotype unaffected by environment;
genetic characteristics inherited/passed on to offspring/ora
/represents alleles possessed; [2 max]
(b) Define the terms
(i) gene;
length of DNA/sequence of bases/locus on a chromosome;
coding for a characteristic/protein/polypeptide/enzyme; [2]
(ii) allele.
alternative form of a gene;
determining contrasting characters/controls one form of a character;
occupies same locus;
ref. sequence of bases;
ref. dominance; [3 max]
[Total : 7]
LGS AS Level Biology [Mark Scheme: Inherited Change ] 4/5
Q4 In mice, the intensity of pigmentation of the fur is controlled by multiple alleles of a single gene.
The alleles are listed below in order of dominance, with C as the most dominant.
• C = full colour
• Cch = chinchilla
• Ch = himalayan
• Cp = platinum
• Ca = albino
(a) Explain how multiple alleles arise.
gene mutation ;
a change in the, base(s) / nucleotide(s) ;
e.g. base, substitution / deletion / addition [2]
(b) Eye colour in mice is controlled by two alleles of a single gene, B/b:
• allele B codes for black eyes
• allele b codes for red eyes.
A mouse with full colour fur and black eyes was crossed with a mouse with himalayan fur and
black eyes. One of the offspring was albino with red eyes.
Using the symbols above, draw a genetic diagram to show the genotypes and phenotypes of the
offspring of this cross.
[6]
[Total: 8]
LGS AS Level Biology [Mark Scheme: Inherited Change ] 5/5
Q6 The fruit fly, Drosophila melanogaster, is widely used in genetic research. It has many phenotypic
variants in features such as body colour, wing shape and eye colour.
Two variations from the normal-winged, grey-bodied phenotype are:
• vestigial (very short) wings, coded for by the recessive allele of the gene N/n
• ebony (black) body colour, coded for by the recessive allele of the gene G/g.
(a) Using the symbols given, state the possible genotypes of normal-winged, grey-bodied fruit flies.
NNGG
NNGg
NnGG
NnGg ;; 4 correct = 2 marks 2/3 correct = 1 mark [2]
(b) Describe how you would determine the genotype of a normal-winged, grey-bodied fly.
[Total: 5]
