topic 2 - cell division (mitosis)

Question 1

what is mitosis

Answer 1

cell division that produces genetically identical cells

Question 2

what are the two types of cell division in eukaryotes

Answer 2

mitosis and meiosis

Question 3

what is mitosis needed for

Answer 3

the growth of multicellular organisms and for repairing damaged tissues

Question 4

what does the cell cycle consist of

Answer 4

a period o called f cell growth and DNA replication called interphase - interphase is subdivided into three separate growth stages - G1, S, G2

Question 5

what happens in gap phase 1 (G1)

Answer 5

the cell grows and new organelles and proteins are made

Question 6

what happens in synthesis (S)

Answer 6

the cell replicates its DNA ready to divide by mitosis

Question 7

what happens in gap phase 2 (G2)

Answer 7

the cell keeps growing and proteins needed for cell division are made

Question 8

what are the four stages of mitosis

Answer 8

prophase, metaphase, anaphase, telophase

Question 9

what happens in interphase

Answer 9

the cell carries out normal functions but also prepares to divide - the cell’s DNA is untravelled and replicated to double its genetic content - the organelles are also replicated so it has spare ones and its ATP content is increased

Question 10

why is the organelles ATP content increased in interphase

Answer 10

because it provides the energy needed for cell division

Question 11

what happens in prophase

Answer 11

the chromosomes condense, getting shorter and fatter - tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle - the nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 12

what happens in anaphase

Answer 12

the centromeres divide, separating each pair of sister chromatids - the spindle fibres contract putting chromatids to opposite poles of the spindle, centimetre first - this makes the chromatids appear v-shaped

Question 13

what happens in metaphase

Answer 13

the chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere

Question 14

what happens in telophase

Answer 14

the chromatids reach the opposite poles on the spindle - they uncoil and become long and thin again - they’re now called chromosomes again - a nuclear envelope form around each group of chromosomes, so there are now two nuclei - the cytoplasm divides (cytokinesis) and there are now two daughter cells that are genetically identical to the original cell and to each other - mitosis is finished and each daughter cell starts the interphase part of the cell cycle to get ready for the next round of mitosis

Question 15

how can you calculate how long each stage of mitosis lasts

Question 16

what is cancer the result of

Answer 16

uncontrolled cell division

Question 17

what are mitosis and the cell cycle controlled by

Answer 17

genes

Question 18

what are mutations

Answer 18

changes in the base sequence of an organism’s DNA

Question 19

how are tumours formed

Answer 19

normally when cells have divided enough times to make enough new cells they stop but if there’s a mutation in a gene that controls cell division the cells can grow out of control - the cells keep on dividing to make more and more cells which form a tumour

Question 20

how do cancer treatments that target the cell cycle work

Answer 20

they are designed to control the rate of cell division in tumour cells by disrupting the cell cycle but doesn’t distinguish tumour cells from normal cells so also kill normal body cells that are dividing - however tumour cells divide more frequently than normal cells so the treatments are more likely to kill tumour cells

Question 21

what are two types of cell cycle targets of cancer treatments

Answer 21

(1) G1 (cell growth and protein production) - chemotherapy
(2) S (DNA replication) - radiation

Question 22

how does chemotherapy treatments work

Answer 22

it prevents the synthesis of enzymes needed for DNA replication - if these aren’t produced, the cell is unable to enter the synthesis phase, disrupting the cell cycle and forcing the cell to kill itself

Question 23

how do radiation treatments work

Answer 23

at several points in the cell cycle DNA is checked for damage - if severe damage is detected the cell will kill itself - preventing further tumour growth