Cell division

Question 1

what is the cell cycle

Answer 1

a highly ordered sequence of events that takes place in a cell

Question 2

what does the cell cycle result in

Answer 2

division of the cell and the formation of two genetically identical daughter cells

Question 3

what are the two main phases of the cell cycle

Answer 3

interphase and mitotic (division) phase

Question 4

why do we need new cells

Answer 4

for growth and repair

Question 5

whats a period of cell division called

Answer 5

M phase

Question 6

what does M phase involve

Answer 6

mitosis and cytokinesis

Question 7

what are the three separate growth stages of interphase

Answer 7

G1, s, G2

Question 8

what happens during interphase

Answer 8

• the cells prepare to divide
• the cell’s DNA is unravelled and replicated
• the organelles are also replicated so it has spare ones and its ATP content is increased

Question 9

what is mitosis needed for

Answer 9

growth an repair

Question 10

what kind of process is mitosis

Answer 10

continuous process but is described as a series of stages

Question 11

what is the chromosomes structure

Answer 11

the chromsomes are made of two strands joined in the middle by a centromere
the separate strands are called chromatids
two strands on the same chromosome are called sister chromatids

Question 12

why is there two strands of chromosomes

Answer 12

each chromosome has already made an identical copy of itself during interphase

Question 13

what happens to the chromosome when mitosis is over

Answer 13

the chromatids end up as one-strand chromosomes in the new daughter cells

Question 14

what happens during prophase

Answer 14

the chromosomes condense
centrioles move to the opposite ends of the ceell, forming protein fibres across called the spindle
- the nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 15

what happens during metaphase

Answer 15

the chromosomes line up along the middle of the cell and become attache to the spindle by their centromere
- at the metaphase checkpoint, the cell checks all the chromosomes are attached to the spindle before mitosis can continue

Question 16

what happens during anaphase

Answer 16

the centromeres divide, separating each pair of sister chromatids
- the spindles contract, pulling chromatids to opposite ends of the cell, centromere first

Question 17

what happens during telophase

Answer 17

the chromatids reahc opposite poles on the spindle
they uncoil and become long and thin again
they are now called chromosomes again
a nuclear envelope forms arounf each group of chromosomes

Question 18

what happens during cytokinesis

Answer 18

the cytoplasm divides
a cleavage furrow forms to divide the cells
two genetically identical daughter cells are formed

Question 19

when does cytokinesis begin

Answer 19

in anaphase

Question 20

when does cytokinesis end

Answer 20

telophase

Question 21

how do investigate mitosis

Answer 21

to do this you treat the tips of the growing roots in HCl and break them open carefully and spread a few on a microscopic slide
- add a few drops of stain
- squash under a coverslip
- view under microscope

Question 22

what are gametes

Answer 22

sperm cells and egg cells

Question 23

what happens during sexual reproduction

Answer 23

two gametes join together at fertilisation to form a zygote

Question 24

what number of chromosomes do gametes have?

Answer 24

a haploid numberw

Question 25

how many chromsomes does a body cell have?

Answer 25

a diploid number

Question 26

what is meiosis

Answer 26

cell division that produce gametes

Question 27

are gametes genetically identical?

Answer 27

no they are genetically different because each cells ends up with a combination of chromosomes

Question 28

what is the first phase of meiosis

Answer 28

interphasein

Question 29

what happens during interphase of meiosis

Answer 29

the cells DNA unravels and replicates to produce double-armed chromosomes (sister chromatids)

Question 30

what is meiosis 1

Answer 30

involves two divisions (M1 and M2)
after interphase the cell enter M1
M1 is the reduction division (it halves the chromosome number)