Meiosis

Question 1

Interphase

Answer 1

• Thread like chromosomes
• Chromosomes replicate (DNA Synthesis)
• Centrioles replicate

Question 2

Prophase 1

Answer 2

-Chromatin condenses and coils chromosomes become visible
-Nuclear membrane breaks down
Nucleolus Disappears
- Spindle starts to form
-Homologous pairs of chromosomes form bivalents
-Bivalents are linked at physical points called chiasmata
-This can lead to the crossing over of chromatids which can cause genetic variation
-Homologous chromosomes repel but remain attached at chiasmata

Question 3

Metaphase 1

Answer 3

-Bivalents line up along the equator attached to the spindle by their centromeres

Question 4

Anaphase 1

Answer 4

• Homologous chromosomes separate and are pulled by the spindle fibres towards opposite poles of the cells
• Independent segregation (random separation of maternal and paternal chromosomes

Question 5

Telophase 1

Answer 5

-Chromosomes reach poles
Often the cell goes straight into meiosis 2
-Spindles disappear
-Nuclear membrane starts to reform
-Cell divides by cytokinesis

Question 6

Prophase 2

Answer 6

• Spindle forms (at right angles to original spindle)

- Nuclear membrane disappears if it had reformed

Question 7

Metaphase 2

Answer 7

-Chromosomes line up at equator attached to spindle by their centromere

Question 8

Anaphase 2

Answer 8

-Centromere divides & chromatids separate

Question 9

Telophase 2

Answer 9

• Chromosomes reach poles & uncoil
• Spindle disappears
• Nuclear Membrane reforms
• Cytoplasm divides (cytokinesis)
• Tetrad of 4 haploid cells