Genetic Variation

Question 1

Meiosis I

Answer 1

Interphase: the DNA replicates so there are now two identical copies of each chromosome (referred to as chromatids).

Prophase I: chromatids condense and arrange themselves into homologous pairs
Crossing over occurs (recombination). The nuclear envelope disintegrates and spindle fibres form.

Metaphase I: homologous chromosomes line up along the equator and attach to the spindle fibre by their centromeres.

Anaphase I: homologous chromosomes are separated

Telophase I: chromosomes reach opposite poles of the cell. Nuclear envelope reforms around the chromosomes. Cytokinesis results in the formation of two daughter cells.

Question 2

Meiosis II

Answer 2

Prophase II: chromosomes condense, nuclear envelope disintegrates and spindle fibres form.

Metaphase II: chromosomes attach to the spindle fibre by their centromeres.

Anaphase II: sister chromatids are separated.

Telophase II: chromatids reach opposite poles of the cell. Nuclear envelope reforms and cytokinesis takes places. Four genetically unique daughter cells are produced.

Question 3

How does meiosis increase genetic variation

Answer 3

Crossing over:
-when the homologous chromosomes move towards each other and exchange genetic material
-Pieces of chromosomes are exchanged and the chromatids separate, forming chromosomes with different combinations of alleles.

Mutations