2.3 Eukaryotic Cell Cycle + Division

Question 1

describe the difference between DNA normally and DNA during cell division

Answer 1

normally, DNA is all tangled

during cell divison, DNA condenses and appears as visible chromosomes

Question 2

describe the process of DNA forming a visible chromosome

Answer 2

1. DNA is a double helix
2. DNA wraps around histone proteins to form a nucleosome
3. nucleosome attaches into chromatin
4. chromatin coils and supercoils and condenses into a visible chromosome

Question 3

describe, in order, the events of the cell cycle

Answer 3

during interphase:
G1- cell assimilates molcules
    - cell grows
S-phase- semi-conservative DNA replication
             -replication of DNA
G2- cell synthesis of more organelles
during mitosis:
prophase
metaphase
anaphase
telophase
cytokinesis

Question 4

give 4 key points of mitosis

Answer 4

• 2 new daughter cells made
• genetically identical to parent cells
• used for growth + replacement
• asexual reproduction

Question 5

what happens during interphase in mitosis

Answer 5

cellular organelles double in number, the DNA replicates, and protein synthesis occurs. the chromosomes are not visible and the DNA appears as uncoiled chromatin

Question 6

what happens during prophase in mitosis

Answer 6

• nuclear membrane and nucleolus break down
• centrioles migrate to opposite poles
• chromatin condenses to form visible chromosomes
• spindle fibres start to form

Question 7

what happens during metaphase in mitosis

Answer 7

• chromosomes attach singly to the equator by centromere

- centromere attaches them on to the spindle fibres

Question 8

what happens during anaphase in mitosis

Answer 8

• centromeres replicate

- sister chromatids split and move to opposite poles

Question 9

what happens during telophase in mitosis

Answer 9

• nuclear membrane and nucleolus reform
• centrioles move away from poles
• chromatins reform (chromosomes decondense)
• spindle fibres break down

Question 10

give 3 ways that growth can be defined as

Answer 10

a permanent increase in number of cells
a permanent increase in the mass of an organism
a permanent increase in the size of an organism

Question 11

what are the three aspects of growth

Answer 11

cell division
assimilation
cell expansion

Question 12

how are worn out or damaged cells replaced

Answer 12

by mitosis

Question 13

describe asexual reproduction

Answer 13

involves one parent
no gametes involved
quicker than sexual reproduction
clones are genetically identical to parent
useful for extreme environments or solitary organisms
lots of different methods

Question 14

describe sexual reproduction

Answer 14

requires two parents 
fusion of gametes occurs
gametes are produced by meiosis
more complex organisms
offspring show genetic variation

Question 15

describe binary fission as a process of asexual reproduction

Answer 15

involves mitosis and cytokinesis to make 2 offspring

Question 16

describe spores as a process of asexual reproduction

Answer 16

involves mitosis and production of asexual spores- each spore grows into a new individual

Question 17

describe regeneration as a process of asexual reproduction

Answer 17

some organisms can replace body parts when lost

Question 18

describe bud production as a process of asexual reproduction

Answer 18

outgrowth from parent organism- a smaller, genetically identical organism is produced that then detaches and becomes independent

Question 19

describe new plant structures as a process of asexual reproduction

Answer 19

vegetative propagation occurs in flowering plants. a new plant is propagated from the parent

Question 20

is a gamete haploid or diploid

Answer 20

haploid

Question 21

define homologous

Answer 21

same genes in the same places

Question 22

what are the male gamete and site of production in animals

Answer 22

sperm cells in testes

Question 23

what are the male gamete and site of production in plants

Answer 23

pollen in anther

Question 24

what are the female gamete and site of production in animals

Answer 24

ovum in ovaries

Question 25

what are the female gamete and site of production in plants

Answer 25

ovum in ovaries

Question 26

give a summary of the two stages of meiosis

Answer 26

MEIOSIS I normal interphase different PMAT to mitosis MEIOSIS II no S-phase in interphase no semi-conservative DNA replication PMAT is the same as mitosis

Question 27

what are the end products of meiosis

Answer 27

four genetically identical haploid gametes

Question 28

describe interphase of meiosis I

Answer 28

same as mitosis | G1 , s-phase and G2 occur

Question 29

describe prophase of meiosis I

Answer 29

nuclear membrane and nucleolus break down centrioles migrate to opposite poles chromatin condenses to form visible chromosomes homologous chromosomes form bivalents crossing over occurs; where nits of maternal and paternal chromosomes are cut and joined at random points called chiasma

Question 30

describe metaphase of meiosis I

Answer 30

independent assortment occurs; either of a pair of homologous chromosomes, maternal or paternal, can move to either pole

Question 31

describe anaphase of meiosis I

Answer 31

whole chromosomes move to opposite poles

Question 32

describe telophase of meiosis I

Answer 32

centrioles move away from poles nuclear membrane and nucleolus reform chromatin reforms spindle fibres break down

Question 33

describe interphase of meiosis II

Answer 33

there is G1 and G2 but no s-phase so no semi-conservative DNA replication occurs

Question 34

describe prophase of meiosis II

Answer 34

nuclear membrane and nucleolus break down centrioles migrate to opposite poles chromatin condenses to form chromosomes spindle fibres start to form

Question 35

describe metaphase of meiosis II

Answer 35

chromosomes attach singly to the equator by centromere | centromere attaches them on to the spindle fibres

Question 36

describe anaphase of meiosis II

Answer 36

centromeres replicate | sister chromatids split and move to opposite poles

Question 37

describe telophase of meiosis II

Answer 37

centrioles move away from poles nuclear membrane and nucleolus reform chromatin reforms spindle fibres break down

Question 38

what is a chromosomal mutation

Answer 38

a change in the large scale structure of a chromosome

Question 39

describe the effect of a non-disjunction mutation on meiosis

Answer 39

during anaphase of meiosis II, the sister chromatids should split and move to opposite poles in non-disjunction mutations, there is a failure of chromosomes splitting so both chromatids go to one poke

Question 40

what effect does a non-disjunction mutation have on the gametes

Answer 40

one gamete will have two copies of a chromosome whereas another gamete will have none.

Question 41

define aneuploidy

Answer 41

too little or too many chromosomes

Question 42

give two examples of aneuploidy

Answer 42

trisomy | monosomy

Question 43

what are the consequences of a non-disjunction mutation

Answer 43

it can be fatal | can cause Down's syndrome, which is trisomy @ 21st chromosome pair