2.3.2- Cell Division

Question 1

What is interphase?

Answer 1

A period of cell growth and DNA replication

Question 2

What are the three growth phases of interphase?

Answer 2

G1 S and G2

Question 3

What happens in Gap phase 1

Answer 3

The cell grows (vol of cytoplasm) and new organelles and proteins are made.

Question 4

What happens in the synthesis phase?

Answer 4

The cell replicates its DNA (semi-conservitively), this leads to 2 identical chromatids joined at a centromere

Question 5

What happens in Gap phase 2

Answer 5

The cell keeps growing and proteins needed for cell division are made.

Question 6

Describe in detail the three main events that occur during interphase.

Answer 6

• DNA is unravelled and replicated to double genetic content
  -Organelles are replicated so it has spare ones
  -ATP content is increased as it is needed for cell division

Question 7

Describe prophase in mitosis.

Answer 7

The chromosomes condense getting dhorther and fatter as ting bundles of proteins being the centrioles move to oppposite ends of the cell forming a network of protein fibres across it called the spindle. The nuclear envelope around the nucleus breaks down and the chromoseomes lie free in the cytoplasm.

Question 8

Describe metaphase in mitosis.

Answer 8

The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.

Question 9

Describe anaphase in mitosis.

Answer 9

The centometres divide, seperating each pair of sister chromatids. The spindles contracts, pulling chromatids to opposite poles (ends) of the spindle, centrometre first. Thsi makes the chromatids appear v- shaped.

Question 10

Describe telephase in mitosis.

Answer 10

The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They are now called chromosomes again. A nuclear envelope forms around each group of chromsomes, so now there are two nuclei. Then cytokineseis occures.

Question 11

Describe cytokinesis

Answer 11

Startes during anaphase and finishes in telephase and is the division of cytoplasm. At the end of it therre are now two daughter cells that are genetically indentical to the origional cell and to eachother. Then each daughter cell starts interphase to do it all over again.

Question 12

Why are there sister chromatids on the chromosome before mitosis begins?

Answer 12

Because during interphase, each chromosome has already made an identical copy of itself?

Question 13

What is a sister chromatid?

Answer 13

Two strands of the same chromosome.

Question 14

Give three uses of mitosis

Answer 14

Growth
Repair
Asexual reproduction

Question 15

What is cancer?

Answer 15

A tumour that invades surroumnding tissue cause by uncontrolled cell division from a mutation in a gene that controlls cell division.

Question 16

Why is cancer treatment more likely to kill cancerous cells than normal cells?

Answer 16

Because cancer cells divide much more frequently than normal cells.

Question 17

Dscribe how some cancer treatments target cell cycles.

Answer 17

During g1 chemotherapy prevents the sythesis of enzymes needed for synthesis causing it to kill itself.
During synthesis radiation and some DNA drugs damage DNA and if sever damage id detected, the cell will kill istelf both preventing tumour growth.

Question 18

In what stage of the cell cycle does all the DNA unravel.

Answer 18

The S phase.

Question 19

What os the mitotic index?

Answer 19

The proportion of cells in a tissue sample that are undergoing mitosis.

Question 20

State the formula to work put the mitotic index

Answer 20

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

Question 21

Give the formula for calculating actual size

Answer 21

Actual Size =Image size (with ruler)÷Magnification

Question 22

State a 2 suitable stains that can be used to investigate mitosis.

Answer 22

Toludoine
Ethano-orcein

Question 23

State the abbreviagtion of formula used to calculate magnification.

Answer 23

IAM

Question 24

What does the name ‘Binary Fission’ refer to

Answer 24

Division in Prokaryotic cells

Question 25

How is binary fission diffferent from normal mitosis?

Answer 25

There is no nuclesr envelope to breakdown
There are no spindle fibres present

Question 26

Describe the process of Binary fission

Answer 26

A single circular DNA molecule molecule undergoes DNA replication and any plasmids present. The parent cell divides into two and cytoplasm is roughkly parted between the two daugher cells.Each daughter cell contains a singular copy of the circular DNA molecule and a variable number of plasmids.

Question 27

How is it ensured each daughter cell inherits a copy of a single DNA moleucle and some plasmids?

Answer 27

If it does not receive the singular circular DNA molecule, or at least one copy of a plasmid the die.

Question 28

How come the daughter cells produced in binary fission can have different no. of plasmids but still be genetically identical?

Answer 28

The contain the same genetic code they just have less or more identical copies of that code.

Question 29

Why cant viruses undergo cell division?

Answer 29

They are parastic meaning they can only reproduve by infecting living cells (host cells).

Question 30

What stage of the cell cycle do cells spend most of their life in?

Answer 30

G1 (Interphase)

Question 31

Where does DNA syntheseis happen in a eukaryotic cell?

Answer 31

Nucleus

Question 32

Describe how to prepare squahses of cells from plant root tips

Answer 32

Cut a thin slice of a root tip(5mm) from end using scalpel and mount onto a slide
Soak root tip in HCl the rinse
Stain for DNA (end toluidine blue)
Lower coverslip using a mounted needle at 45” not trapping ait bubbles
Squash by firmly pressing down on a glass slip

Question 33

Why are root tips used in Practical 2?

Answer 33

That is where mitosis occurs

Question 34

Why is a stain used in practical 2

Answer 34

To distinguish chromosmes which are not visible otherwise

Question 35

Why press dwon on the cover of the slip when using an optical microscope to identify the stages of mitiosis

Answer 35

Thois creates a single layer of cells so light passes throught to make chromosomes visible

Question 36

Why is it important to not oush the slip sideways in Practical 2?

Answer 36

To avoid rolling cells tg and breaking chromosmes

Question 37

Why are root tips soaked in HCL in Practical 2?

Answer 37

This seperates cells/ cells walls allowing stain to diffuse into cells.This allows cells to be more easily squashed and it stops mitosis

Question 38

Descibe how to set up and use an optical microscope

Answer 38

Clip slide onto stage and turn on the light
Set power to lowest objective lens
Use coarse focusng dial to move stage close to lens then turn coarse focusing dial to move away from lens u till image comes into focus.
Add fine focusing dial to get clear image
Swap to higher objective power lens then refocus

Question 39

Describe how viruses replicate

Answer 39

Their attachment proteins attach to complementary receptors on host cells
This injects its viral RNA/DNA into the host cell
Infected host cell replicates virus particles
Nucleic acid replicated so cell produces protein/ caspid/enzymes
Virus is assmepled and then released