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Date May 2018 Marks available 2 Reference code 18M.2.HL.TZ2.3
Level Higher level Paper Paper 2 Time zone Time zone 2
Command term Identify 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]
b.

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, FfIA IB 

b. Punnett square with correct gametes shown 

c. correct probability:  1 8

                                   OR
                                   12.5%

Must use blood type symbols IB IA and i. No specific letters required to represent cystic fibrosis allele though dominant and recessive must be apparent.

b.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.

Syllabus sections

Additional higher level » Topic 10: Genetics and evolution » 10.1 Meiosis
Core » Topic 3: Genetics » 3.3 Meiosis
Core » Topic 3: Genetics
Additional higher level » Topic 10: Genetics and evolution
Core
Additional higher level

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