Cells: All cells arise from other cells

Question 1

Define tumour:

Answer 1

A swelling in an organism made up of cells that continue to divide in an abnormal way.

Question 2

What type of cell division produces genetically identical cells?

Answer 2

Mitosis

Question 3

What do the newly produced cells from mitosis replace?

Answer 3

Old/damaged cells

Question 4

What is a diploid cell?

Answer 4

A cell that has two sets of chromosomes.

Question 5

What type of cell division produces diploid cells?

Answer 5

Mitosis

Question 6

What are haploid gametes?

Answer 6

Sex cells that have half the normal amount of chromosomes.

Question 7

What type of cell division produces haploid gametes?

Answer 7

Meiosis

Question 8

What are the two main stages that make up the cell cycle?

Answer 8

• Interphase
• Mitosis

Question 9

What are the three stages that occur in interphase?

Answer 9

• Growth stage 1
  -Synthesis of DNA (S-phase)
  -Growth stage 2

Question 10

What happens in stage Growth stage 1 during interphase?

Answer 10

• Replication of organelles, e.g. mitochondria, ribosomes

Question 11

What happens in synthesis of DNA stage during interphase?

Answer 11

• Replication of DNA (DNA content will double)

Question 12

What happens in growth stage 2 during interphase?

Answer 12

• Checks that cell is ready for mitosis

Question 13

In what stage of interphase does cell cycle arrest occur?

Answer 13

G1

Question 14

What happens in cell cycle arrest?

Answer 14

• Cell cycle stops
• Cell ‘rests’

Question 15

What are checkpoints in the cell cycle?

Answer 15

Stages where the cell is checked to ensure that it is ready to move on to the next phase of the cell cycle.

Question 16

What are checkpoints controlled by?

Answer 16

Genes that code for proteins

Question 17

What is created through mitosis?

Answer 17

Two genetically identical daughter cells

Question 18

Give three reasons why mitosis is important in the life of an organism:

Answer 18

• Allows the creation of new body cells for growth and repair
• Replaces old/damaged cells
• Embryo formation

Question 19

Give three reasons why meiosis is important in the life of an organism:

Answer 19

• Haploid gametes are produced, allowing fertilisation
• Genetic variation
• Restoring chromosome number

Question 20

What are the four stages of mitosis?

Answer 20

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 21

What happens in prophase?

Answer 21

• Chromosomes condense, becoming shorter, fatter and visible
• Spindle fibres begin to form
• Nuclear envelope breaks down; chromosomes become free in the cytoplasm

Question 22

What happens in metaphase?

Answer 22

• Chromosomes line up at the cells equator
• Chromosomes attach to spindle fibres by their centromeres

Question 23

What happens in anaphase?

Answer 23

• Chromosomes divide at their centromere, separating the pair of sister chromatids.
• Spindle fibres contract, pulling the chromatids to opposite poles of the cell centromere first.

Question 24

What happens in telophase?

Answer 24

• Chromatids reach the opposite poles of the cell and uncoil, becoming long.
• Nuclear envelope forms around each set of chromosomes
• The cell splits into two (cytokinesis)

Question 25

What is cytokinesis?

Answer 25

The reforming of the cell membrane/wall and the separation that produces two genetically identical daughter cells.

Question 26

What is a centriole?

Answer 26

Organelles that produces spindle fibres

Question 27

What is the role of the centromere in mitosis?

Answer 27

Allows chromosomes to move towards the opposite poles of the cell.

Question 28

How does chemotherapy work?

Answer 28

- Prevents enzyme synthesis (required for DNA replication) - S phase will not occur - DNA cannot be replicated = division cannot occur

Question 29

How do drugs work to treat cancer?

Answer 29

- Prevent spindle fibres from forming - One cell will have 2x normal amount of chromosomes, one cell will have none. - Cells are faulty and cannot divide.

Question 30

How does radiotherapy work?

Answer 30

- Damages cells DNA. - Cell will not pass checkpoints in S phase - Causes apoptosis

Question 31

What is a carcinogen?

Answer 31

A chemical form of radiation or other agent that causes cancer

Question 32

What is the centromere?

Answer 32

The centre structure within a chromosome that joins the chromatids.

Question 33

What is a clone?

Answer 33

A group of genetically identical organisms formed from a single parent by asecual reproduction.

Question 34

What is differentiation?

Answer 34

The process by which a cell becomes specialised for different functions.

Question 35

What are homologous chromosomes?

Answer 35

A pair of chromosomes (one maternal, one paternal) that have the same gene loci and determine the same features.

Question 36

What is a mutagen?

Answer 36

Any agent that induces a mutation

Question 37

What is a mutation?

Answer 37

A sudden change in the amount or arrangement of the genetic material in a cell

Question 38

What is a photomicrograph?

Answer 38

A photograph of an image produced by a microscope

Question 39

What are stem cells?

Answer 39

Undifferentiated dividing cells that occur in embryos and adult animal tissues that require constant replacement.

Question 40

What is the tumour suppressor gene?

Answer 40

A gene that maintains normal rates of cell division and prevents the development of tumours.

Question 41

Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of this:

Answer 41

More cells can be produced to replace damaged/old cells.