Edexcel IAL Biology 3.10 Meiosis and genetic variation

Track homologous chromosomes and chromatids through the diagram, name the correct meiotic event and connect new allele combinations to variation in gametes.

Exam points

Explain crossing over between non-sister chromatids at chiasmata in prophase I.
Explain independent assortment through random homologous-pair orientation at metaphase I.
Complete chromosome or gamete diagrams with the correct chromosome and chromatid number.

[Maximum number: 3]

The photograph shows a mother and baby Malayan tapir (Tapirus indicus). They live in the rainforests of southeast Asia. Each gamete of a Malayan tapir contains 26 chromosomes.

Figure for Question 3.10—Meiosis and genetic variation question 1 — Edexcel A-Level Biology AS

The body cells of the mother Malayan tapir have some genetic similarities to and differences from the cells of her baby. Explain why the body cells of the mother and baby have genetic similarities and differences.

An explanation that makes reference to three of the following points:

- (the body cells of) baby will have $\{26$ / half the $\}$ chromosomes that are \{similar / identical\} to those in the mothers (cells) (1)

- the other $\{26$ / half of $\}$ chromosomes in the baby body cells will be (genetically) different as they came from the \{sperm cell / father\} (1)

- (there may be genetic differences in the gamete chromosomes inherited from the mother) due to \{mutation / crossing over\} (1)

ACCEPT \{genetic material / DNA / alleles\} for chromosomes

IGNORE genes

ACCEPT baby has inherited \{26 / half\} of the chromosomes from the mother IGNORE genetic similarities unqualified IGNORE inherited some chromosomes from mother

ecf for 13

ACCEPT baby has inherited \{26 / half\} of the chromosomes from the father IGNORE inherited some chromosomes from father

IGNORE \{independent / random\} assortment

IGNORE incorrect stage of meiosis

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3.10—Meiosis and genetic variation question 1