Mitosis

Question 1

what are the three phases of the cell cycle

Answer 1

1. interphase
2. nuclear divison(mitosis)
3. cytokinesis

Question 2

what happens during interphase

Answer 2

the cell increases in mass and size for cell division by synthesising proteins and replicating its DNA

Question 3

what are the 3 phases interphase consists of

Answer 3

• g1 phase
• s phase
• g2 phase

Question 4

explain the G1 phase

Answer 4

Cells make the RNA, enzymes and other proteins required for growth

Question 5

explain the S stage

Answer 5

• the DNA in the nucleus replicates by semi-conservative replication resulting in each chromosome consisiting of two identical sister chromatids

Question 6

explain the G2 phase

Answer 6

• the cell continues to grow in preperation for mitosis
• microtubules are produced which form the mitotic spindle

Question 7

what are the 4 stages of mitosis

Answer 7

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 8

explain 3 ways that mitosis is fundamental to biological processes

Answer 8

1. growth of multicellular organisms - mitosis enables zygotes to grow into multicellular organisms
2. replacement of cells and repair of tissues - damaged tissues can be repaired by mitosis
3. asexual reproduction - the offspring are genetically identical to the parent

Question 9

explain what happens during prophase

Answer 9

• chromosomes condense and are now visible
• two centrioles move towards opposite poles of the cell
• spindle fibres begin to emerge from the centrioles
• the nuclear envelope breaks down

Question 10

explain what happens during metaphase

Answer 10

• chromosomes line up at the equator of the cell
• chromosomes attach to the spindle fibres by their centromers

Question 11

explain what happens during anaphase

Answer 11

• spindle fibres shorten and centromere splits
• this pulls the sister chromatids to opposite poles of the cell

Question 12

explain what happens during telophase

Answer 12

• chromosomes arrive at opposite poles nd begin to uncoil
• the spindle fibres break down
• nuclear envelope begins to reform around each set of chromosomes

Question 13

explain what happens during cytokinesis

Answer 13

• the cytoplasm divides forming two genetically identical cells

Question 14

what is the formula to calculate mitotic index

Answer 14

mitotic index = number of cells with visible chromosomes / total number of cells

Question 15

what is cancer

Answer 15

uncontrolled mitosis

Question 16

a changes in the base sequence of a gene is known as a _______

Answer 16

mutation

Question 17

what are carcinogens

Answer 17

• any agent that may cause cancer

Question 18

some tumours do not spread from their original site, these are known as _____

Answer 18

benign
* they do not cause cancer

Question 19

some tumours spread through the body, invading and destroying other tissues. These are known as _____

Answer 19

malignant

Question 20

what is the process of cell division in prokaryotic cells called

Answer 20

binary fission

Question 21

explain the process of binary fission

Answer 21

1. the single, circular DNA molecule undergoes DNA replication
2. any plasmids present undergo DNA replication
3. the parent cell divides into two cells, with the cytoplasm roughly halved
4. the two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids