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Date	May 2018	Marks available	3	Reference code	18M.2.HL.TZ2.3
Level	Higher level	Paper	Paper 2	Time zone	Time zone 2
Command term	Determine	Question number	3	Adapted from	N/A

Question

The micrograph shows a plant cell of Lilium grandiflorum during meiosis.

Identify, giving reasons, the stage of meiosis shown by this cell.

[2]

a.i.

Outline the law of independent assortment.

[2]

a.ii.

The genes for cystic fibrosis and blood group are not linked. Two parents are heterozygous for cystic fibrosis. One parent has blood group O and the other has blood group AB. Using a Punnett square, determine the probability that their child will have both cystic fibrosis and blood group A.

[3]

Markscheme

a. anaphase II

b. as four daughter cells are being formed
OR
the centromeres split / sister chromatids separate
OR
sister chromatids/ chromosomes are pulled «by the spindle microtubules» to opposite poles

a.i.

a. two «or more» traits/genes are inherited independently of one another. Accept vice versa.

b. observed for traits/genes that are not linked/far apart on the chromosome
Can be shown in annotated diagram.

c. «due to homologous» chromosomes aligning independently/randomly on equator during metaphase I/meiosis I

d. during anaphase I homologues pulled to separate poles

Can be shown in annotated diagram.

a.ii.

a. correct parental genotypes shown / Ff ii, FfI^A I^B

b. Punnett square with correct gametes shown

c. correct probability: $\frac{1}{8}$

OR
12.5%

Must use blood type symbols I^B I^A and i. No specific letters required to represent cystic fibrosis allele though dominant and recessive must be apparent.

Examiners report

[N/A]

a.i.

[N/A]

a.ii.

[N/A]

Syllabus sections

Core » Topic 3: Genetics » 3.4 Inheritance

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