Meiosis

Question 1

Meiosis

Answer 1

• Two-stage cell division that takes place in reproductive organs
• Results in the formation of four genetically different haploid daughter cells
• Haploid gametes are essential so that following fertilisation the diploid number of chromosomes is restored

Question 2

Meiosis stages

Answer 2

-Interphase

-Meiosis I:
Prophase I
Metaphase I
Anaphase I
Telophase I

Cytokinesis

Meiosis II (Same as Mitosis):
Prophase II
Metaphase II
Anaphase II
Telophase II

Cytokinesis

Question 3

Meiosis I

Answer 3

Prophase I:

• Synapsis occurs where the paternal and maternal chromosomes come together as a homologous pair
• This homologous pair is called a bivalent
• The pair of chromosomes cross over and swap sections of genes, which leads to genetic variation
• Centrosomes move to the poles
• Nuclear envelope breaks down

Metaphase I:

• Bivalents meet at equator of the cell
• Paternal and maternal chromosomes arrange randomly which gives rise to variation

Anaphase I:

• Homologous chromosomes in each bivalent separate as spindle fibres shorten
• Each pole receives one of each homologous chromosome
• There is random mixture of paternal and maternal chromosome due to their random arrangement at Metaphase I

Telophase I:

• The homologous pairs separate with one chromosome from each going into separate nuclei
• Nuclear membrane reforms
• Spindle fibres disintegrate

Cytokinesis: Forms two genetically different haploid daughter cells

Question 4

Meiosis II

Answer 4

Prophase II:

• Nuclear envelope broken down again
• centrioles separate

Metaphase II:

• Spindle fibres attach to chromosomes at centromere
• Chromosomes arrange themselves on the equator of the spindle fibres

Anaphase II:

• Spindle fibres shorten and centromere divides
• Chromatids pulled to opposite poles

Telophase II:

• The chromatids uncoil
• Spindle fibres disintegrate
• Nuclear envelope and nucleoli reform

Cytokinesis: Forms four genetically different haploid daughter cells