Cell continuity

Question 1

Mitosis prophase

Answer 1

chromosomes condense and become visible

Nucleolus disappears and nuclear membrane breaks down

centrioles move to opposite ends of the cell and spindle fibres begin to form

Question 2

Mitosis metaphase

Answer 2

chromosomes align in the equator of the cell

spindle fibres attach to the centromeres

Question 3

Mitosis anaphase

Answer 3

centromeres split and the spindle fibres contract, this pulls the chromatid apart

Question 4

Mitosis telophase

Answer 4

sister chromatids end at opposite polls of the cell

chromatids decondense and become less visible
Nucleolus reappears and nuclear membrane reforms

spindle fibres disappear

Question 5

Mitosis cytokineses

Answer 5

cell divides and to produce 2 diploid daughter cells

Question 6

Meiosis prophase 1

Answer 6

homologous chromosome pairs pair up to form bivalents

chromosomes condense and become more visible

nucleolus disappears and nuclear membrane breaks down

in late prophase, chromosomes repel to reveal chiasmata

in animal cells, centrioles migrate to opposite ends of the cell

crossing over takes place in prophase 1

Question 7

Meiosis metaphase 1

Answer 7

chromosome pairs (bivalent) align in the equator of the cell

spindle fibres attach to centromeres of each chromosome

Question 8

Meiosis anaphase 1

Answer 8

spindle fibres contract and pull full chromosomes apart from their pair (bivalent) to opposite sides of cell

this ensures that each daughter cell will have one of each pair chromosome

Question 9

Meiosis telophase 1

Answer 9

chromosome pulled to opposite poles of cell

nuclear membrane begins to reform and nucleolus reappears

chromsomes decondense and become less visible

Question 10

Meiosis 1 cytokinesis

Answer 10

produces 2 haploid daughter cells

Question 11

Meiosis 2 prophase 2

Answer 11

chromosomes stay in their condensed form and new spindles are formed at right angles to the old ones

Question 12

Meiosis 2 metaphase 2

Answer 12

chromosomes each consisting of 2 chromatids align in the equator

Question 13

Meiosis 2 anaphase

Answer 13

spindles contract and chromatids pull apart to opposite ends of the cell

Question 14

Meiosis 2 telophase 2

Answer 14

chromsomes elongate and spindle fibres disappear

nuclear membrane reforms + nucleolus

Question 15

meiosis 2 cytokinesis

Answer 15

produces 4 haploid daughter cells

Question 16

cytokinesis in animal cells

Answer 16

cleavage furrow forms as cell surface membrane invaginates and splits into 2

caused by the shortening of cytoskeleton fibres

Question 17

cytokineisis in plants

Answer 17

cell plate is laid down along the centre of the cell

vesicles forming along the equatorial plate fuse and cytoplasm divides

Question 18

what is a diploid organism?

Answer 18

have their chromosomes arranged in homologous pairs within the cell

Question 19

What is a chromosomes structure?

Answer 19

extended DNA molecule supported by histones that are folded into compact stacks and the DNA is coiled tightly around it known as a nucleosome
nucleosomes help protect and support DNA

Question 20

why are histones so important?

Answer 20

They provide support for DNA when chromatin condenses to form visible chromosomes during nuclear division

Question 21

what are the differences between meiosis and mitosis?

Answer 21

meiosis occurs in reproductive organs such as the ovaries or the testes or pollen grains

meiosis involves 2 divisions and produces 4 haploid daughter cells

the chromosome arrangement in the daughter cells are both different to each other and the parent cells ( ALL GENETICALLY DIFFERENT)

Question 22

what is G1 phase

Answer 22

G1 phase is when organelles and other cytoplasmic components replicate / form

the cell will also increase in size

Question 23

what is s phase

Answer 23

S phase is when DNA is duplicated and chromatids form with the nucleus

this is also where histones are formed

Question 24

what is G2 phase

Answer 24

G2 is when spindle proteins are synthesised
it is also where chromosomes are checked for error and repaired if necessary

this is a second growth phase for the cell

Question 25

where do all phases of mitosis occur in

Answer 25

interphase, an active phase where many metabolic processes take place as the cell prepares for division

Question 26

what happens at G1 checkpoint

Answer 26

this checkpoint is at the end of G1 phase and checks the cell has reached a critical size there is enough nutrients available for the next stage the necessary growth regulator factors are in place there is no DNA damage

Question 27

what happens if a cell doesn't meet he requirements at G1 checkpoint

Answer 27

it will enter the G0 known as the resting phase, this phase can be short, long or permenant depending on the internal and external factors of the cell. the cells within G0 are suspended from cell division but can still carry out normal cell functions

Question 28

what cells can never enter G0

Answer 28

cells in epithelial tissue

Question 29

what cells dont return to cell cycle

Answer 29

highly differentiated cells

Question 30

what happens at G2 checkpoint

Answer 30

This checkpoint is after G2 phase this checkpoint checks that DNA replication has taken place accurately and that there is no DNA damage the cell can start mitosis if there is no problems

Question 31

what happens if the cell requirements are met at G1 checkpoint

Answer 31

the cell will enter the S phase where DNA synthesis occurs

Question 32

how is cancer caused

Answer 32

uncontrolled cell division

Question 33

can cancer cells enter G0

Answer 33

NO

Question 34

what is cancer involved in

Answer 34

the breakdown in the ability of the checkpoints to regulate the process of cell division

Question 35

what is an example of the inhibition of micro tubules formation and what type of drug is it classified as

Answer 35

vincristine mitotic poisons

Question 36

what happens with vincristine

Answer 36

vincrisitne binds with the tubules in the microtubules and prevents them from functioning properly it stops the formation of microtubules which means no spindle fibres will be produced it can also stop the spindle fibres contracting and pulling chromatids apart thus preventing anaphase

Question 37

whats an example of an antimetabolites

Answer 37

fluorouracil

Question 38

what does it do?

Answer 38

act as s phase inhibitors preventing DNA synthesis as it inhibits an enzyme involved in making nucleotides that contain the base thymine, preventing DNA synthesis

Question 39

what happens to DNA in preparation for mitosis

Answer 39

the cell content doubles to provide enough DNA for new chromosomes to be synthesised

Question 40

what does mitotic division do

Answer 40

maintain the state of ploidy

Question 41

what is reduction division

Answer 41

cell division that halves the number of chromosomes in gametes

Question 42

independent assortment

Answer 42

in meiosis - only one chromosome from each homologous pair can enter a gamete however, for any gamete it can be either of the 2 homologous pairs that actually enter the particular gamete

Question 43

what is a gamete

Answer 43

reproductive cell

Question 44

what does ploidy mean

Answer 44

the number of chromosomes in each cell

Question 45

when does independent assortment occur

Answer 45

when the chromosomes line up at the cell equator in metaphase 1 of meiosis

Question 46

crossing over

Answer 46

2 non sister chromatids break and exchange sections with each other

Question 47

when does crossing over occur

Answer 47

during prophase 1

Question 48

what is the point of crossing over called

Answer 48

chiasmata

Question 49

if the alleles of the chromosomes differ what are the consequences

Answer 49

2 chromatids of the same chromosome are no longer genetically identical some chromatids may contain unique sequences of alleles that didnt exist in the parental chromosome

Question 50

what is a gene locus

Answer 50

the position of a gene on the chromosome

Question 51

when is crossing over complete

Answer 51

metaphase 1