12.6 Cell Cycle And Cell Division

Question 1

Interphase

Answer 1

Period between divisions

Question 2

What 3 stages is interphase in?

Answer 2

1. G1 phase
2. S phase
3. G2 Phase

Question 3

G1 phase

Answer 3

Cell increases in size and new biomass is made

Question 4

S phase

Answer 4

DNA replicates by semi conservative replication

Question 5

G2 phase

Answer 5

Cell prepares for division, synthesis and stores of ATP and new organelles synthesised

Question 6

Nuclear division (mitosis and meiosis)

Answer 6

Period when the nucleus divides into 2 (mitosis) or 4 (meiosis)

Question 7

Cell division (cytokinesis)

Answer 7

Cytoplasm divides to produce 2 new cells or 4 new cells

Question 8

Not all cells go through all parts of cell cycle particularly…

Answer 8

Differentiated cells

Question 9

Gene is…

Answer 9

A section of dna that codes for one specific polypeptide

Question 10

Chromosome

Answer 10

Independent DNA molecule which has been supercoiled into a condensed form (contains many different genes)

Question 11

Centromere

Answer 11

2 genetically identical copies of the DNA molecule are made and attached at this central point

Question 12

Each of DNA copies…

Answer 12

Supercoil using histone proteins to help them coil in eukaryotes

Question 13

Chromosome number js represented by

Answer 13

n

Question 14

homologous chromosomes

Answer 14

Same genes in the same gene loci but different alleles of the genes (one maternal and one paternal)

Question 15

Prophase

Answer 15

Chromosomes supercoil and become visible

1) nuclear membrane breaks down
2) centrioles start to move to the poles of the cell and make spindle fibres
3) chromosomes supercoil and condense/shorten/thicken and become visible
4) each chromosome appear as 2 identical sister chromatids joined at the centromere

Question 16

Metaphase

Answer 16

Chromosomes line up on the equator of cell

1) centrioles complete the production of spindle fibres
2) chromosomes are attached to spindle fibres by their centromere
3) chromosomes align down the equator of the cell

Question 17

Anaphase

Answer 17

Spindles get shorter, centromere splits identical sister chromatids separate

1) spindle fibres shorter
2) centromere splits
3) identical sister chromatids are pulled to opposite poles
4) making a “V” shape

Question 18

telophase

Answer 18

two nuclei

1) nuclear membrane starts to reform around each set of chromosomes
2) chromatids/chromosomes unwind become longer/thinner and become invincible

Question 19

Describe the appearance and behaviour of chromosomes during mitosis (5marks)

Answer 19

1. During prophase chromosomes supercoil and condense to become visible
2. Chromosomes appear as 2 identical sister chromatids joined by centromere
3. During metaphase chromosomes line up on the equator of the cell
4. Chromosomes attach to spindle fibres
5. By their centromeres
6. During anaphase, centromere splits
7. Sister chromatids are pulled to opposite poles of the cell making V shape
8. During telophase chromatids uncoil and become thinner

Question 20

Allele

Answer 20

one of a number of alternative forms of the same gene

Question 21

As cells are produced…

Answer 21

The differentiate and produce various tissues, organs and organ systems and the whole organism

Question 22

once tissues have been formed…

Answer 22

Cell divisions stopped

Question 23

Tumour suppressor genes

Answer 23

Codes for proteins that slow down the cell cycle

Question 24

Proto-onco genes

Answer 24

Codes for proteins that speed up cell cycle

Question 25

Example of control genes

Answer 25

- tumour suppressor genes - proto-onco genes

Question 26

If a mutation occurs in one of these control genes…

Answer 26

Cell division continues uncontrolled

Question 27

Describe uncontrolled division

Answer 27

It’s often rapid and cells produced are abnormal. Tumour develops If cells start to spread into the tissue/body, the tumour is regarded as a cancer

Question 28

How cancer is treated

Answer 28

Drugs to inhibit cell division These drugs may stop: DNA replication, spindle formation, cytokinesis or other processes linked to mitosis

Question 29

Binary fission

Answer 29

Replication of Circular DNA Division of cytoplasm Replication of Plasmids

Question 30

What 2 solutions does the plant need to be soaked into before observation

Answer 30

50 °C Hydrochloric acid Ethano-orcein stain

Question 31

Why add Ethano-orcein stain

Answer 31

To stain the chromosomes (adds contrast) so they can be viewed under the microscope.

Question 32

why add 50 °C Hydrochloric acid

Answer 32

To break down the cellulose cell walls, ensuring the stain can enter and the tissue and the root tissue can be squashed into a layer one cell thick so that light passes through the thin sample of tissue /cells.

Question 33

How do you calculate mitotic index

Answer 33

MI= number of cells in PMAT / total number of visible cells

Question 34

Serial dilution formula

Answer 34

M1 X V1 = M2 X V2 M1 = Desired diluted concentration (mol dm-3) V1 = Desired Volume (cm3) M2 = Original concentration (mol dm-3) V2 = Unknown Volume of stock solution (cm3)