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Date November 2017 Marks available 2 Reference code 17N.2.HL.TZ0.05
Level Higher level Paper Paper 2 Time zone TZ0 / no time zone
Command term Describe Question number 05 Adapted from N/A

Question

Describe the process of crossing over.

[2]
a.

Explain the reason for linked genes not following the pattern of inheritance discovered by Mendel.

[2]
b.

Markscheme

a. occurs during prophase I/during meiosis

b. homologous chromosomes form bivalents/pair up

c. breakage and rejoining of chromatids

d. exchange «of DNA/alleles» between non-sister chromatids/homologous chromosomes

[Max 2 Marks]

a.

a. «linked genes are» on the same chromosome

b. Mendel's genes were on different chromosomes

c. linked genes are inherited together

    OR

    no independent assortment

d. «linked genes» only separated by crossing over

    OR

    fewer recombinants than with unlinked genes

Reject sex-linkage

b.

Examiners report

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

Syllabus sections

Additional higher level » Topic 10: Genetics and evolution
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