mitosis

Question 1

what happens during prophase?

Answer 1

• chromosomes become visible due to the condensation of chromatin & each chromosome consists of 2 sister chromatids joined at the centromere
• the nucleolus disappears, & in animal cells, the centrosomes migrate to opposite poles of the cell
• the spindle fibres extend from each pole towards the equator of the cell
• the nuclear envelop breaks down, where the nuclear lamina & nuclear pore complexes dissociate, & the nuclear envelop fragments turn into vesicles

Question 2

what happens during metaphase?

Answer 2

• the spindle fibres attach to the kinetochore at the centromere of the chromosome
• the chromosomes arrange themselves 90° to the spindle axis in a single row, at the metaphase plate of the cell

Question 3

what happens during anaphase?

Answer 3

• the centromere of each chromosome divides, causing the sister chromatids of each chromosome to separate
• the sister chromatids move to opposite poles of the cell, centromere first, due to the shortening of the spindle fibres
• the cell elongates as the non-kinetochore spindle fibres lengthen

Question 4

what happens during telophase?

Answer 4

• the sister chromatids reach the respective poles of the cell & become chromosomes of the daughter cells
• the chromosomes uncoil & become chromatin, while the nucleolus in each nucleus reappears
• the nuclear envelope reforms around the chromosomes at each pole, where the nuclear membrane vesicles fuse, & the nuclear lamina and nuclear pore complexes reassemble
• the spindle fibres break down

Question 5

can cytokinesis be observed during telophase?

Answer 5

YES

Question 6

what is the significance of mitosis?

Answer 6

• mitosis maintain the genetic stability of an organism or a cell from 1 generation to the next,
• as the 2 daughter cells formed are genetically identical to the parent cell,
• and the daughter cells have the same number & types of chromosomes as the parent cell

Question 7

how does mitosis maintain genetic stability from 1 generation of cells to the next?

Answer 7

1. DNA replication occurs in the parent cell before mitosis begins, with the amount of DNA being doubled during S phase of interphase, and halved after cytokinesis
2. the chromosomes are arranged at the equator of the cell during metaphase
3. sister chromatids separate during anaphase, & are equally distributed between the 2 nuclei during telphase

Question 8

when does mitosis occur?

Answer 8

• during growth & development of a multicellular organism
• during the replacement of cells or worn-out tissues of the body
• during an immune response

Question 9

how is mitosis the basis of asexual reproduction?

Answer 9

this is because the offspring produced will be identical to the parents, allowing a population to rapidly colonise a habitat

Question 10

what are the 2 factors affecting the length of the cell cycle

Answer 10

-

Question 11

do prokaryotes undergo mitosis during asexual reproduction?

Answer 11

• no, they undergo binary fission