MITOSIS AND CELL CYCLE

Question 1

Role of mitosis

Answer 1

Asexual reproduction/binary fission
Growth (embryogenesis)
Repair injury or replacing cells
Differentiation of stem cells

Question 2

Role of meiosis

Answer 2

Sexual reproduction
Production of haploids (gametes)
Increases genetic variation

Question 3

What is the cell cycle

Answer 3

All cells arise from other cells
Cells are always in one of the phases of the cell cycle
Not all cells in multicellular organisms retain the ability to divide

Question 4

Mitosis in adults

Answer 4

.Neuronal cells once differentiated dont undergo mitosis and stay in the rest position
New neurones are generally not produced in adults
.most tissues in the body are replenished in a similar way to skin tissue where stem cells divide to produce new differentiated cells
.an epidermal stem cell undergoes mitosis to produce a non- replicating epithelial cell and another stem cell to continue genesis

Question 5

Describe how chromosomes change during the cell cycle

Answer 5

Before a cell can divide it needs to grow and increase the number of sub cellular structures such as ribosomes and mitochondria
The DNA replicates to form two copies of each chromosome
One set of chromosomes is pulled to each end of the cell and the nucleus divides
Finally the cytoplasm and cell membranes divide to form two identical cells

Question 6

what is a chromosome

Answer 6

a genetic material that has all the features and characteristics of an organism

Question 7

cycle in more detail

Answer 7

chromosomes shorten and thicken
chromosomes have two identical chromatids due to replication
chromatids move to the equator
attach to individual spindle fibres
spindle fibres contract and centromeres divide
chromosomes move to opposite poles
each pole receives identical copies of each chromosome
nuclear envelope forms around each group of chromosomes at each pole

Question 8

what is cancer

Answer 8

a disease resulting from cells that break away from an original tumor to form a secondary tumor elsewhere in the body (metastasis)

Question 9

what is a tumor

Answer 9

a swelling that is made up of cells that continue to divide in an abnormal way

Question 10

what is metastasis

Answer 10

the spread of tumor forming cells usually through blood stream or lymph nodes to form secondary tumors

Question 11

what are checkpoint controls

Answer 11

a cells surveillance mechanism which ensures that the cell cycle (hence cell growth) happens only when necessary and correctly

Question 12

which proteins carry out the checkpoint control

Answer 12

1. growth factors
2. cyclins- coded for by tumor suppressor genes and proto-oncogenes

Question 13

sometimes checkpoints are ineffective, what is the effect of this

Answer 13

can cause cancer

Question 14

two types of mutations

Answer 14

gene
chromosome

Question 15

what are gene mutations

Answer 15

mutations that affect small regions of DNA, usually one base
occur during DNA replication during mitosis

Question 16

what are chromosome mutations

Answer 16

mutations that affect large regions of DNA that is contained within chromosomes
occur during metaphase of meiosis

Question 17

what are mutagenic agents

Answer 17

rate of reaction is increased by mutagenic agents

Question 18

two types of mutagenic agents

Answer 18

carcinogens
mutagen

Question 19

what is a carcinogen

Answer 19

causes a mutation in one cell that leads to tumor growth

Question 20

what is a mutagen

Answer 20

causes mutation in a cell or entire organism that can be inherited

Question 21

3 types of mutagen

Answer 21

radiation
chemicals
viruses

Question 22

describe radiation

Answer 22

high energy ionising radiation such as x-ray, UV, or alpha radiation, ionise bases or affect bonding of correct base pairs

Question 23

describe chemical mutagens

Answer 23

intercalating (seperates DNA strands)
e.g. mustard gas, agent orange, asbestos

Question 24

describe viruses mutagen

Answer 24

some viruses such as HPV can change the base sequence in DNA causing genetic disease and cancer