MEIOSIS

Question 1

Produces

Answer 1

4 haploid cells as gametes

Question 2

How many divisions and what are they called

Answer 2

2
Meiosis 1 and 2

Question 3

Interphase 1

Answer 3

Cell grows, copies its chromosomes and prepares for cell division
G0 - cell leaves the cell cycle due to death or differentiation.
G1 - cellular contents excluding the chromosomes are duplicated.
S - each of the 46 chromosomes are duplicated in DNA replication
The cell “checks” the duplicated chromosomes for errors and makes repairs

Question 4

Prophase 1

Answer 4

Chromosomes condense and become visible in the DIPLOID CELL
Bivalents form (2 homologous chromosomes)
Chiasma form and crossing over occurs
Centrioles begin to migrate to poles
Spindle fibres form microtubules and attach to centromeres
Nuclear envelope breaks down
Nucleolus disappears

Question 5

Crossing over

Answer 5

Non-sister chromatids exchange alleles
They become entangled and the crossing points are chiasmata
The entanglement places stress on the DNA molecules
As a result a section of chromatid from one chromosome breaks and rejoins with the chromatid from another chromosome
Makes them genetically identical, a type of translation.

Question 6

Metaphase 1

Answer 6

Spindle fibres move bivalents to the centre of the cell
Chiasmata remain attached

Question 7

anaphase 1

Answer 7

Spindle fibres contract and pull on centromeres
Centromeres remain intact but chromosomes separate in each bivalent

Question 8

Telophase 1 and cytokinesis

Answer 8

Chromosomes arrive at poles of cell
Spindle fibres break down
Nuclear envelope formed
Nucleolus reforms (NOT in plant cells)
Cytoplasm splits into two forming 2 new HAPLOID daughter cells

Question 9

Prophase 2

Answer 9

Nuclear envelope and nucleolus disperse
Centrosomes and centrioles replicate and move to opposite poles of the cell

Question 10

Metaphase 2

Answer 10

Centrioles at the polls of the cell produce spindle fibres
Chromosomes align randomly across the equator of the spindle
Chromosomes are attached to the spindle by centromere

Question 11

Anaphase 2

Answer 11

Centromeres detach and the chromatids separate
Spindle fibres shorten and pull chromatids towards opposite ends of the dividing cell
A complete set of chromatids migrate to the opposite side of the cell

Question 12

Telophase 2 and cytokinesis

Answer 12

Chromatids have separated and are now chromosomes again
Chromosomes start to decondense to form chromatin
Spindle fibres disintegrate and new nuclear envelope starts to form
A contractile ring, made of myosin and actin filaments assembles equatorially
Myosin 2 uses the free energy released when ATP is hydrolysed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow
Continued hydrolysis causes this cleavage furrow to ingress
The parent cells become 4 genetically different HAPLOID cells