3.2.2 all cells arise from other cells

Question 1

what is produced by mitosis and what are they used for?

Answer 1

-genetically identical cells unless there is a mutation of DNA
-produced by asexual reproduction so are diploid
-used to replace old/damaged cells, growth and embryonic formation

Question 2

What is produced through meiosis?

Answer 2

-haploid gametes: sex cells which only contain one set of chromosomes

Question 3

What are the 2 stages in the cell cycle?

Answer 3

-interphase
-mitosis

Question 4

What phases are within interphase and what happens in each one?

Answer 4

-1st growth phase: replication of organelles. Can enter cell cycle arrest where replication stops
-s-phase: DNA synthesis
-2nd growth phase

Question 5

What do cells pass through after each stage in the cell cycle?

Answer 5

-checkpoints
-these are genes which code for proteins which control the cell cycle

Question 6

what are the 4 stages of mitosis?

Answer 6

-prophase
-metaphase
-anaphase
-telophase

Question 7

What happens in prophase?

Answer 7

-chromosomes condense and become shorter, fatter and visible
-spindle fibres begin to form
-the nuclear envelope breaks down and the chromosomes are free in the cytoplasm

Question 8

What happens in metaphase

Answer 8

-chromosomes line up along the equator
-chromosomes attach to spindle fibres by their centromere

Question 9

What happens in anaphase?

Answer 9

-chromosomes divide at the centromere, separating the sister chromatids
-spindle fibres contract
-chromatids are pulled to opposite sides of the cell

Question 10

What happens in telophase

Answer 10

-chromatids uncoil and become long and thin known as chromosomes
-a nuclear envelope forms
-cell splits into two in a process called cytokinesis

Question 11

What happens during cytokinesis

Answer 11

-physical separation of the parent cell into 2 genetically identical daughter cells
-cell membrane/ wall forms

Question 12

What causes cancer

Answer 12

-mutations in the genes that control cell division causing cells to grow out of control

Question 13

What will happen if the cancer cells pass through the checkpoints

Answer 13

-they will continue to divide via mitosis
-the cells will layer on top of each other forming a tumour.
-these can can cause blockages or damage to other organs
-they need their own blood supply but often they suffer from low oxygen and the blood supply can’t satisfy the tumours oxygen demand causing necrosis

Question 14

Malignant tumours

Answer 14

-grow quickly and will invade other tissues
-they will break off and spread around the body causing tumours in other organs (metastasis)
-more likely to become life threatening

Question 15

Benign tumours

Answer 15

-tumour grows slowly and is kept in one place
-they don’t invade other tissues and start tumours in other areas and organs
-not usually life threatening

Question 16

how do you calculate mitotic index

Answer 16

Number of cells in mitosis/ total cells

Question 17

How does chemotherapy work?

Answer 17

-prevents the synthesis of the enzymes needed for DNA replication
-meaning the cell cycle stops before the S-phase
-so cells can’t divide

Question 18

How does radio therapy work

Answer 18

-damages the DNA meaning the cell won’t pass the checkpoint in the s-phase
-forces the cell to kill itself (apoptosis)
-cells won’t divide

Question 19

How do cancer drugs work?

Answer 19

-prevents the formation of spindle fibres
-so stops anaphase
-means one cell will have double the amount of DNA and the other will have none
-prevents the cell from functioning or dividing again

Question 20

What does a virus cell contain?

Answer 20

-capsid
-reverse transcriptase
-genetic information
-lipid envelope
-attachment proteins

Question 21

How are viruses replicated?

Answer 21

-virus attaches via attachment proteins to specific receptors on cell surface membrane
-capsid is injected into host cell (the capsid contains the genetic material)
-genetic material is incorporated into the host DNA
-protein synthesis makes viral proteins
-these assemble and burst out of cells

Question 22

How is HIV replicated

Answer 22

-HIV attachment proteins bind to specific receptors on the cell surface membrane on T-helper cells
-Nucleic acid/ RNA enters cell
-the reverse transcriptase turns the RNA into DNA
-protein synthesis makes viral proteins
-these assemble and burst out of cells

Question 23

How does bacterial replication by binary fission work

Answer 23

-circular DNA and plasmids replicate
-cytoplasm divides
-cell wall reforms

Question 24

Why do bacteria replicate via binary fission

Answer 24

prokaryotes have no centrioles so no there is no spindle fibres so sister chromatids can’t be separated