2.6.2 mitosis

Question 1

chromatids

Answer 1

replicates of chromosomes

Question 2

cytokinesis

Answer 2

division of cytoplasm of cell following mitosis

Question 3

mitosis

Answer 3

type of nuclear division that maintains chromosome number
- each new daughter cell contains same genetic info as parent cell
- genetically identical to each other (daughter cells)

Question 4

reasons for living organisms needing to produce genetically identical daughter cells via mitosis

Answer 4

• asexual reproduction
  –> single celled protoctists divide by mitosis to produce new individuals
• growth
  –> all multicellular organisms grow by producing more genetically identical cells
• tissue repair
  –> wounds heal when growth factors stimulate proliferation of endothelial/smooth muscle cells (repair damaged blood vessels)

Question 5

what are growth factors secreted by

Answer 5

• platelets & macrophages (white blood cells)
• damaged cells of blood-vessel walls

Question 6

stages of mitosis

Answer 6

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 7

events during stage 1 - prophase

Answer 7

• chromosomes (that have replicated in S phase of interphase & consist of 2 identical sister chromatids) shorten & thicken as DNA supercoils
• nuclear envelope breaks down
• centriole (animal cells) divides & 2 new daughter centrioles move to opposite poles
• cytoskeleton protein (tubulin) threads form a spindle between centrioles –> plant cells = tubulin threads formed from cytoplasm

Question 8

events during stage 2 - metaphase

Answer 8

• pairs of chromatids attach to spindle threads at equator region (metaphase plate)
• attach by centromeres

Question 9

events during stage 3 - anaphase

Answer 9

• centromeres of each pair of chromatids split
• motor proteins (walking along tubulin threads) pull each sister chromatid, in opposite directions, to poles
• (as centromere first) the chromatids, now called chromosomes, assume a V shape

Question 10

events during stage 4 - telophase

Answer 10

• separated chromosomes reach poles
• nuclear envelope forms around each set of chromosomes
• cell contains 2 nuclei –> genetically identical

Question 11

what occurs after mitosis/telophase

Answer 11

cytokinesis = cell splits in 2

Question 12

cytokinesis in animal cells

Answer 12

plasma membrane folds inwards & ‘nips in’ cytoplasm

Question 13

cytokinesis in plant cells

Answer 13

• end plate forms where equator of spindle was
• new plasma membrane/cellulose cell wall material laid down on either side along end plate

Question 14

what does mitosis form

Answer 14

2 new genetically identical daughter cells
–> genetically identical to parent cell too