2.1.6 Meiosis

Question 1

Meiosis is…

Answer 1

Special type of cell division that is responsible for the production of gametes

Question 2

Homologous pair?

Answer 2

Two chromosomes that have the same genes in the same sequence; one of each comes from each parent

Question 3

Gametes are different to body cells because…

Answer 3

They are haploid; not identical, show genetic variation; four daughter cells produced

Question 4

Gamete examples?

Answer 4

Sperm + eggs in animals; pollen + eggs in plants; spores in some plants and fungi

Question 5

Meiosis begins during…

Answer 5

Puberty for mammalian males; before birth for mammalian females

Question 6

Before meiosis…

Answer 6

Interphase occurs, checkpoints are worked through

Question 7

Meiosis 1 step 1, prophase 1

Answer 7

Occupies +90% of meiosis time; chromosomes begin to condense and nuclear membrane disappears; in synapsis homologous chromosomes pair up to form bivalents (aligned gene by gene)

Question 8

Synapsis?

Answer 8

Process of forming bivalents

Question 9

Bivalents?

Answer 9

Pairs of chromosomes joined by genes, only happens in meiosis

Question 10

Meiosis 1 step 2, metaphase 1?

Answer 10

Bivalents line up at the equator of cell; orientation of each bivalent is random and independent of each other

Question 11

Meiosis 1 step 3, anaphase 1?

Answer 11

Homologous pairs in the bivalent are pulled to opposite ends of the cell, but sister chromatids remain joined together

Question 12

Meiosis 1 step 4, telophase 1?

Answer 12

Chromosomes start to disperse; nuclear envelope reforms; cleavage furrow begins to form

Question 13

There is no…

Answer 13

Interphase between meiosis 1 and 2

Question 14

Meiosis 2 step 1, prophase 2?

Answer 14

Chromosomes still made up of two sister chromatids; condense to become visible; nuclear envelope breaks down (2 cells attached to one another)

Question 15

Meiosis 2 step 2, metaphase 2

Answer 15

Chromosomes line up at equator of cell and attach to spindle fibres

Question 16

Meiosis 2 step 3, anaphase 2

Answer 16

Chromatids pulled to poles of cell; chromosome from each pair is pulled to other end of cell

Question 17

Meiosis 2 step 4, telophase 2

Answer 17

Chromatids disperse and become less visible, nuclear envelope reforms; 4 haploid cells are formed

Question 18

Crossing over?

Answer 18

Chromatids of homologous chromosomes twist around one another, crossing over many times; portions of the chromatid are exchanged; genetic information is swapped (same genes)

Question 19

Chiasmata?

Answer 19

Point of chromatid breakage during crossing over

Question 20

Recombinant chromosomes?

Answer 20

Chromosomes that have crossed over

Question 21

Independent / random assortment is due to…

Answer 21

Separation of chromosomes at each stage