T2: The Cell Cycle and Mitosis

Question 1

what is the cell cycle?

Answer 1

interphase
nuclear division (mitosis)
cell division (cytokinesis)

Question 2

what is mitosis?

Answer 2

the part of the cell cycle in which a eukaryotic cell divides to produce two genetically identical daughter cells

Question 3

what are the stages of mitosis?

Answer 3

PMAT
Interphase before
Cytokinesis after

Question 4

why is mitosis needed?

Answer 4

produces 2 genetically identical cells for growth and repair

Question 5

describe interphase

Answer 5

cell prepares to divide: energy stores increase + cell gets bigger
organelles are replicated
DNA is unravelled and copied

Question 6

describe prophase

Answer 6

chromosomes condense and are now visible when stained

the chromosomes consist of two sister chromatids joined together at the centromere

the two centrosomes move towards opposite poles
spindle fibres begin to emerge from the centrosomes
the nuclear envelope breaks down into small vesicles

Question 7

describe metaphase

Answer 7

each centrosome reaches a opposite pole
chromosomes line up across the equator of the spindle, attached by their centromeres

Question 8

describe anaphase

Answer 8

centromeres divide separating each pair of sister chromatids
spindle fibres begin to shorten pulling sister chromatids to opposite ends of the cell

Question 9

describe telophase

Answer 9

chromatids reach opposite poles and uncoil
spindle fibres break down and a nuclear membrane forms around DNA

Question 10

how many chromosomes do human diploid cells have?

Answer 10

46 chromosomes

before the parent cell undergoes mitosis there is 92 in the nucleus

Question 11

what can be seen during prophase?

Answer 11

chromosomes are visible
nuclear membrane is breaking down

Question 12

what can be seen during metaphase?

Answer 12

chromosomes are lined up along the middle of the cell

Question 13

what can be seen during anaphase?

Answer 13

chromosomes are moving away from the middle of the cell, towards opposite poles

Question 14

what can be seen during telophase?

Answer 14

chromosomes have arrived at opposite poles of the cell
chromosomes begin to decondense
the nuclear envelope is reforming

2 groups of chromosomes (one at each pole)

Question 15

why do you place root tips in ethanol?

Answer 15

helps to “fix” the tissue and prevent mitosis from continuing in the cells

Question 16

why do you place root tips in warm HCl?

Answer 16

separates the cells

Question 17

why do you press down on the coverslip after adding it to a specimen on a slide?

Answer 17

spreads out the cells so they are all one layer thick

Question 18

how to calculate mitotic index?

Answer 18

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

Question 19

what causes cancer?

Answer 19

uncontrollable cell division

cancers start when mutations occur in the genes that control cell division
most mutations either result in early cell death or result in the cell being destroyed by the immune system

cancerous cells do not die so can be passed on

Question 20

what are benign tumours?

Answer 20

tumours that do not spread from their original site
do not cause cancer

Question 21

what are malignant tumours and why is it difficult to treat them?

Answer 21

malignant tumours spread through the body
+ interfere with the normal functioning of the organ / tissue
their cells can break off and travel through the blood to form secondary growths
it can be difficult to detect, locate and remove secondary cancers

Question 22

what are plasmids?

Answer 22

smaller, circular DNA molecules that are also replicated and inherited
the number of copies of plasmids that each cell inherits can vary

Question 23

describe binary fission in prokaryotes

Answer 23

the single, circular DNA molecule undergoes DNA replication
any plasmids present undergo DNA replication

the parent cell divides into two cells, with the cytoplasm roughly halved between two daughter cells

the two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids

Question 24

describe the appearance of chromosomes during prophase

Answer 24

chromosomes become visible and appear as two sister chromatids joined at the centromere

Question 25

describe the appearance of chromosomes during metaphase

Answer 25

chromosomes line up on the equator of the cell
they are attached to spindle fibres by their centromeres

Question 26

describe the appearance of chromosomes during anaphase

Answer 26

the centromere splits
sister chromatids are pulled to opposite ends of the cell

Question 27

describe the appearance of chromosomes during telophase

Answer 27

chromatids unwind becoming longer