Mitosis And Meiosis

Question 1

Stages of the cell cycle

Answer 1

Interphase:
G1
S phase
G2

Mitosis
Cytosine

Question 2

G1 phase

Answer 2

Cellular contents excluding chromosome are duplicated. Normal metabolism.

Question 3

S phase

Answer 3

Each of the chromosomes is duplicated by the cell.

Question 4

G2

Answer 4

The cell double checks the duplicated chromosomes for weeks, making any necessary repairs, proteins produced for cytoskeleton.

Question 5

G0 phase

Answer 5

Cell cycle arrest. Stop of cell division, differentiation and specialisation.

Question 6

Terminally dofferentiated

Answer 6

Cells which can no longer divide

Question 7

Centrosomes

Answer 7

Microtubule organising centre - at spindle poles

Question 8

Kinetochore microtubules

Answer 8

Microtubules holding onto chromosomes

Question 9

Daughter cells

Answer 9

Cells produced as a result of mitosis or meiosis of a parent cell

Question 10

Chromatin

Answer 10

The mixture of DNA and protein from which chromosomes are made

Question 11

Spindle apparatus

Answer 11

A set of fine tubular protein fibre that span the cell from pole to pole

Question 12

Haploid

Answer 12

Cells in which there is only one copy of each chromosome.

Question 13

Prophase

Answer 13

Chromosomes become visible, spindle apparatus forms, nucleolus disappears and nuclear envelope breaks down.

Question 14

Anaphase

Answer 14

The spindle fibres contract, causing the two chromatids of each chromosomes to separate and move to the piles of the cell.

Question 15

Metaphase

Answer 15

Chromosome arrange themselves on the equator of the spindle attached by their centromeres.

Question 16

Telophase

Answer 16

The chromosomes reach the poles and a new nuclear envelope forms around each set, the chromosomes uncoil, becoming invisible.

Question 17

Meristem cells

Answer 17

Special areas of plants that undergo cell division. Located in shoot and root tips and under bark for girth growth,

Question 18

Formation of cleavage furrow in animals

Answer 18

Mitosis is followed by actin and myosin micro filaments forming a ring around plasma membrane. Contracts and pulls in membrane.

Question 19

Formation of cell plates in plants

Answer 19

Following mitosis, vesicles carrying cell all and membrane components are delivered to the lane of division. Vesicles fuse and cell plate grows outwards.

Question 20

Mitosis definition

Answer 20

Process of asexual reproduction into which cell divides into two exact replicas.

Question 21

Meiosis definition

Answer 21

Type of cellular reproduction in which number of chromosomes are reduced by half through separation of homologous chromosomes, forming four daughter cells.

Question 22

Sources of genetic variation (list)

Answer 22

Crossing over
Independent assortment of chromosomes at metaphase 1
Independent assortment of chromatids at metaphase 2
Random fertilisation
Mutation

Question 23

Random fertilisation

Answer 23

Takes place when two gametes fuse as any make gamete can fertilise egg

Question 24

Gene mutation

Answer 24

Bases can change during DNA replication and mutations in gametes will be present in all cells of offspring.

Question 25

Crossing over during meiosis

Answer 25

Homologous chromosomes align, chromosomes crossover at chiasmata, and forms recombinant chromosomes.

Question 26

Prophase 1

Answer 26

Chromosomes condense, nuclear envelope disintegrates, nucleolus disappears and spindle formation begins, as with mitosis. Homologous chromosomes pair up forming bivalents, sister chromatids become entangled, breaking off and rejoining at points called chiasmata, sometimes resulting in an exchange of DNA forming recombinant chromosomes.

Question 27

Metaphase 1

Answer 27

Same at mitosic metaphase but homologous pairs of chromosomes assemble along metaphase plate. Randomly orientated, thus independent assortment causing genetic variation.

Question 28

Anaphase 1

Answer 28

Homologous chromosomes are pulled to the opposite poles, but sister chromatids stay joined together. Crossing over finishes as the break leaving recombinant DNA with exchanged alleles and so genetic variation.

Question 29

Telophase 1

Answer 29

Same as telophase in mitosis. Chromosomes assemble at like and nuclear membrane reforms, chromosomes uncoil, cytokinesis and cell is now haploid.

Question 30

Prophase 2

Answer 30

Chromosomes condense and become visible, spindle formation and breakdown of nuclear envelope.

Question 31

Metaphase 2

Answer 31

Individual chromosomes assemble on metaphase plate. Chromatids are no longer identical because of crossing over so there is independent assortment again and more genetic variation produced .

Question 32

Anaphase 2

Answer 32

Chromatids of individual chromosomes are pulled to opposite poles after the division of the centromere as in mitosis.

Question 33

Telophase 2

Answer 33

Chromatids assemble at the poles as in telophase of mitosis, chromosomes uncoil and form chromatin, nuclear envelope reforms and nucleolus becomes visible again. Cytokinesis follows.