(02) Cell Division

Question 1

define somatic cell

Answer 1

body cell

Question 2

define germ cell

Answer 2

egg in females and sperm in males
involved in reproductive cell division

Question 3

define diploid / haploid

Answer 3

haploid has 23 chromosomes
diploid has full set of 46 chromosomes

Question 4

stages of interphase

Answer 4

G1 = growth phase
S = synthesis of DNA
G2 = Growth / gap phase 2

Question 5

describe G1

Answer 5

general life is happening for the cell… cells grow and get larger, many ORGANELLES duplicate

Question 6

describe S phase

Answer 6

DNA replication
ends up with two copies of all DNA in the cell - NOTE THIS IS DIFFERENT FROM RNA TRANSCRIPTION - we do not cover DNA replication process

Question 7

describe G2

Answer 7

doing a number of checks in preparation for Mitotic phase
replication of centrosomes completed

Question 8

name the four stages of the mitotic phase

Answer 8

Prophase
Metaphase
Anaphase
Telophase + cytokinesis

Question 9

Describe prophase for mitosis

Answer 9

Forming mitotic spindle (made of microtubules (tubulin))
Nucleus condenses into chromosomes
Nuclear envelope disappears so chromosomes are more free

Question 10

describe metaphase

Answer 10

condensed chromosomes align in the middle
spindles pull it

Question 11

describe anaphase

Answer 11

spindle fibres contract, separating chromosomes to opposite poles of the cell

Question 12

describe telophase

Answer 12

nuclear envelope reforms
cleavage

Question 13

in what forms does DNA exist in each stage of cell division?

Answer 13

usually exists as chromatin (soup)
prophase - condenses into 2 identical sister chromatids per chromosome (attached at centromere)
anaphase - sister chromatids separate

Question 14

the result of cell division

Answer 14

two daughter cells that are genetically identical to the parent cell

Question 15

where are mitotic cell checkpoints located

Answer 15

three key checkpoints: G1, end of G2, M

Question 16

what is checked during the M phase checkpoint?

Answer 16

that all chromosomes are attached to spindles (in the pro-meta phase)

Question 17

where does meiosis occur?

Answer 17

occurs in the gonads (ovaries and testes)

Question 18

what does meiosis produce

Answer 18

gametes = haploid cells
they are GENETICALLY DIFFERENT from the parent cell
from diploid to haploid cells - daughter cells have exactly half the number of chromosomes

Question 19

what are homologous pairs

Answer 19

one maternal and one paternal chromosome that pair up during fertilisation
carry the same genes but not necessarily the same alleles of those genes

Question 20

name the two stages of meiosis and the main functions

Answer 20

Meiosis I = separates homologous chromosomes
Meiosis II = separates sister chromatids

because both the homologous pairs AND sister chromatids must be separated

so one starting cell can produce four gametes

Question 21

describe prophase I in Meiosis

Answer 21

synapsis - two sister chromatids of each pair of homologous chromosomes pair up, forming a TETRAD

recombination - non-sister chromatids within these tetrads then cross over

Question 22

describe metaphase I in Meiosis

Answer 22

homologous PAIRS line up at the metaphase plate
(at random! = random assortment, so gametes with different sets of homologues are formed)

Question 23

describe anaphase I and telophase I in Meiosis

Answer 23

homologues separate to opposite sides of cells (sister chromatids remain attached)
cleavage, newly formed cells are haploid (2n???)

Question 24

describe Meiosis II

Answer 24

very similar to mitosis
sister chromatids line up at the middle of the cell
sister chromatids separate in anaphase II
haploid (1n) daughter cells form (4 gametes total per parent) \

Question 25

differences in DNA replication for mitosis and meiosis

Answer 25

DNA replication occurs during interphase before mitosis, and also interphase before Meiosis I but NOT before Meiosis II

Question 26

what are sources of genetic variation as a result of meiosis?

Answer 26

crossing over at prophase = recombination
independent assortment at metaphase
fusion between two gametes