mitosis

Question 1

define mitosis

Answer 1

process of nuclear division to produce two genetically identical daughter cells

Question 2

describe the events in prophase (mitosis)

Answer 2

chromosomes condense (and become visible)

the nuclear envelope disintegrates
(the nucleolus disappears)

Question 3

describe the events in metaphase (mitosis)

Answer 3

centrosomes reach opposite poles

spindle fibres extend from centrosomes to attach to the centromere of a chromosome

chromosomes line up at the equator

Question 4

describe the events in anaphase (mitosis)

Answer 4

chromatids separate at the centromere

spindle fibres contract to pull chromatid to their pole

Question 5

describe the events of telophase (mitosis)

Answer 5

chromosomes decondense

nuclear envelope and nucleolus starts to reform around each set of chromosomes

spindle fibres break down

Question 6

what is mitosis fundamental for

Answer 6

1. growth of multicellular organisms
2. replacement of damaged cells/repair of tissue
3. asexual reproduction

Question 7

define meiosis

Answer 7

form of nuclear division that results in the production of haploid cells

Question 8

describe the events of prophase 1

Answer 8

DNA condenses

chromosomes arranged in homologus pairs cross over (as bivalents)

crossing over occurs at the chiasma

nuclear envelope disintegrates and centrioles migrate to opposite poles

Question 9

describe the events of metaphase 1

Answer 9

bivalents line up along the equator of the spindle

spindle fibres attach to the centromeres

independent assortment occurs
( so the proportion of paternal or maternal chromosomes tha tend up on each side of the equator is due to chance)

Question 10

describe the events of anaphase 1

Answer 10

homologus pairs of chromosomes separate as microtubules pull whole chromosomes to opposite ends

(centromeres do not divide)

Question 11

telophase 1

Answer 11

chromosomes arrive at opposite poles

spindle fibres breaks down

nuclear envelope forms around two groups of chromosomes (and nucleolus reforms)

Question 12

describe how cytokinesis occurs

Answer 12

cell surface membrane pinches inward to create a cleavage furrow which then contracts to divide the cytoplasm in half

Question 13

describe prophase 2

Answer 13

nuclear envelope breaks down

chromosomes condense

spindle forms perpendicular to the old one

Question 14

describe metaphase 2

Answer 14

chromosomes line up at the equator

Question 15

anaphase 2

Answer 15

centromeres divide

chromatids pulled to opposite poles

Question 16

telophase 2

Answer 16

nuclear membrane forms around the group of chromatids

then cytokinesis occurs

Question 17

how is meiosis significant

Answer 17

genetically different offspring may be advantageous for natural selection

crossing over and independent assortment create genetic variation as they result in a different combination of alleles

Question 18

define crossing over in meiosis

Answer 18

process by which non-sister chromatids exchange alleles at chiasma

section of chromatid break off and rejoin with a chromatid from another chromosome

Question 19

describe independent assortment in meiosis

Answer 19

production of different combination of alleles in daughter cells due to random alignment of homologous pairs along the equator

Question 20

how can mutations affect the genetic variation of a species?

Answer 20

random mutations occur within genes

during DNA replication

leading to the production of new alleles