Topic 5 - The Mitotic Cell Cycle

Question 1

How long is DNA

Answer 1

2nm

Question 2

What is the Centromere

Answer 2

Holds the two chromatids together. There are not genes in this region. It is the region that becomes attached to the spindle fibres in divison

Question 3

What do telomeres do

Answer 3

They prevent parts of genes being lost after DNA replication and stop uncontrolled cell division.

Question 4

Why are telomeres important

Answer 4

Because they prevent uncontrolled cell division, which can lead to tumors which can be cancerous

Question 5

What are Chromatids [2]

Answer 5

They contain 1 DNA molecule, which is composed of genes.
They are held together by a centromere formed during interphase.

Question 6

What is a centrosome

Answer 6

An organelle made up of two centrioles, near the nucleus in animal cells and is involved in the formation of the spindle prior to nuclear divison.

Question 7

What is chromatin [3]

Answer 7

A material containing protein,
it is present in the nucleus of eukaryotic cells at interphase,
and turns into DNA

Question 8

When are chromosomes visible

Answer 8

When stained during nuclear division

Question 9

What are sister chromatids

Answer 9

Either of the two identical chromatids formed by the replication of a chromosome

Question 10

What are the components that make up a chromosome [5]

Answer 10

• DNA
• Histone Protein
• Sister chromatids
• Centromere
• Telomeres

Question 11

What is the purpose of Mitosis [3]

Answer 11

Produces 2 genetically identical daughter cells for:
- Growth
- Cell Replacement
- Asexual reproduction

Question 12

What is the cell cycle

Answer 12

Regulated cycle of cell division with intermediate periods of growth

Question 13

Outline the stages of the cell cycle

Answer 13

1. Interphase
2. Mitosis
3. Cytokinesis

Question 14

Outline what happens during interphase [3]

Answer 14

• G1 - Cell synthesises proteins for replication (e.g. tubulin for spindle fibres), cell size doubles
• S - DNA replicates, chromosomes consist of two sister chromatids joined at a centromere
• G2 - Organelles divide

Question 15

What are the 4 stages of mitosis

Answer 15

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 16

Outline what happens in prophase [3]

Answer 16

1. Chromosomes condense and become visible X shaped, two sister chromatids joined at centromere
2. Centrioles move to opposite poles of the cell and mitotic spindle fibres form
3. Nuclear envelope and nucleolus break down, leaving chromosomes free in the cytoplasm

Question 17

Outline what happens during metaphase

Answer 17

Sister chromatids line up at the cell equator attached to the mitotic spindle by their centromeres

Question 18

Outline what happens during anaphase [3]

Answer 18

1. Spindle fibres contract, centromeres divide
2. Sister chromatids separate into two distinct chromosomes and are pulled to opposite poles of the cell (looks like V shape)
3. Spindle fibres break down

Question 19

What does anaphase require to happen

Answer 19

ATP from hydrolysis

Question 20

Outline what happens during telophase [3]

Answer 20

1. Chromosomes decondense and can no longer be observed
2. New nuclear envelopes form around each set of chromosomes - two new nuclei each with one copy of each chromosome
3. Cytoplasm constricts

Question 21

What happens during cytokinesis [2]

Answer 21

1. Cell membrane cleavage furrow forms
2. Contractile division of cytoplasm

Question 22

What are telomeres made up of

Answer 22

Multiple repeats of short sequence DNA that cap chromosome tips

Question 23

What are stem cells

Answer 23

Cells that are specialised and retain the ability to differentiate into a range of cell types

Question 24

What are the 4 types of stem cell

Answer 24

• Totipotent
• Pluripotent
• Multipotent
• Unipotent

Question 25

What are totipotent stem cells

Answer 25

can develop into any cell type including the placenta and embryo

Question 26

What are Pluripotent stem cells

Answer 26

can develop into any cell type excluding the placenta and embryo

Question 27

What are multipotent stem cells

Answer 27

can only develop into a few different cell types

Question 28

What are unipotent stem cells

Answer 28

can only develop into one type of cell

Question 29

What are 2 uses of stem cells

Answer 29

1. Repair of damaged tissue
2. Drug testing on artificially grown tissues.

Question 30

Why is regulation of the cell cycle important

Answer 30

Irregular growth of cells where repair is not required can result in the formation of cell masses, which can lead to cancer