Week 1 - Mitosis and the Cell Cycle

Question 1

What are the two types of cell division, and what are they?

Answer 1

Mitosis - results in two identical daughter cells

Meiosis - results in four haploid cells

Question 2

What are the key roles of cell division?

Answer 2

1. Reproduction
2. Growth and Development
3. Tissue Renewal

Question 3

What can uncontrolled cell division lead to?

Answer 3

Tumours

Question 4

What is the difference between the terms chromatin, chromosome, heterochromatic, euchromatin, and chromatid

Answer 4

Chromatin = a complex of DNA and protein that condenses during cell division

Chromosome = molecules of DNA

Heterochromatin = chromatin that is condensed and not transcriptionally active

Euchromatin = chromatin that is less condensed and is transcriptionally active

Chromatid = each copy of a replicated chromosome.

Question 5

What is a genome?

Answer 5

All genetic material in a cell

Question 6

What is a centromere?

Answer 6

The constriction or link between sister chromatids

Question 7

What is a kinetochore?

Answer 7

A specialised protein structure involved in cell division

Question 8

What are telomeres?

Answer 8

The end regions of a eukaryotic chromosome with characteristic telomeric sequences

Question 9

What are the two arms of a chromosome called, and what distinguishes them?

Answer 9

P arm (usually the short arm)
Q arm (usually the longer arm)

Question 10

What is telomerase?

Answer 10

An enzyme that protects telomeres from shortening

Question 11

How many chromosomes and pairs of chromosomes does a human have?

Answer 11

46 chromosomes and 23 pairs (22 chromosome pairs and one sex chromosome pair)

Question 12

How many chromosomes do human gamete cells have?

Answer 12

23

Question 13

How many chromosomes do human somatic cells have?

Answer 13

46

Question 14

What are the two main phases of the cell cycle, and what occurs during each?

Answer 14

Interphase - cell grows, carries out normal functions and copies its chromosomes ready for cell division.

Mitotic Phase - The cell undergoes cell division where DNA is compacted and genes are inactive.

Question 15

What are the three subphases of interphase?

Answer 15

G1 = Normal cell functions
S1  = When a cell copies its chromosomes
G2 = When the cell has twice as much DNA

Question 16

What is the basic role of the mitotic spindle?

Answer 16

Controls chromosome movement during mitosis

Question 17

What occurs during prometaphase?

Answer 17

Some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes.

Question 18

What are the two types of microtubules called, and what’s the difference?

Answer 18

Kinetochore microtubules attach to the kinetochore, while nonkinetochore microtubules do not.

Question 19

What are kinetochores?

Answer 19

Protein complexes associated with centromeres

Question 20

What occurs during metaphase?

Answer 20

All chromosomes are lined up at the metaphase place, an imaginary structure at the midway point between the spindle’s two poles.

Question 21

What occurs during anaphase?

Answer 21

Sister chromatids separate, microtubules shorten by depolymerising at their kinetochore ends, and nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell.

Question 22

What occurs during telophase?

Answer 22

Genetically identical daughter nuclei form at the opposite ends of the cell.

Question 23

At what point does the process of cytokinesis begin?

Answer 23

During anaphase or telophase,

Question 24

What is cytokinesis?

Answer 24

The physical separation of one cell into two daughter cells

Question 25

How is cytokinesis different in plant vs animal cells?

Answer 25

In animal cells, a contractile ring forms around the cell membrane, which then pinches the cell, separating it into two daughter cells. In plant cells, a cell plate forms in the centre of the cell, eventually forming a cell wall, which divides the cell into two daughter cells.

Question 26

How do prokaryotes reproduce?

Answer 26

By a process called binary fission.

Question 27

Explain the process of binary fission

Answer 27

The DNA ring replicates two forms of two identical DNA rings, which then move to opposite sides of the cell. Then the cell divides into two daughter cells.

Question 28

What came first, mitosis or binary fission?

Answer 28

Mitosis is thought to be the evolved version of binary fission.

Question 29

What three cell cycle checkpoints and criteria must be true for the cycle to progress to the next stage?

Answer 29

G1 – Cell size is adequate, nutrients are sufficient, social signals are present, DNA is undamaged G2 – Chromosomes have replicated successfully, DNA is undamaged, activated MPF is present M – All chromosomes are attached to the spindle apparatus.

Question 30

What is MPF and what is its function?

Answer 30

MPF (Mitosis-promoting Factor), also known as maturation promoting factor, is a protein kinase that drives the cell cycle

Question 31

How does MPF activate?

Answer 31

MPF is made of the cyclin-dependant kinase (Cdk) that is active only when bound to the cyclin subunit

Question 32

What is a kinase?

Answer 32

An enzyme that transfers phosphate groups to product energy

Question 33

What are two types of physical signals that can control mitosis, and how do they function?

Answer 33

Anchorage dependence – where cells anchor to a surface and divide Density-dependent inhibition – where cells cover a certain area, they stop dividing.

Question 34

What is the process whereby a normal cell is turned into a cancerous cell?

Answer 34

Transformation

Question 35

What is the difference between a tumour and cancer?

Answer 35

Tumours may be benign (non-cancerous) or malignant (cancerous). Malignant tumours can spread to surrounding tissue. Benign tumours remain localised

Question 36

What is the difference between benign, malignant, and metastatic tumours?

Answer 36

Benign tumours remain in a single location. Malignant tumours spread to surrounding tissue and can metastasize. Metastatic tumours spread from a malignant tumour and spread to another part of the body.

Question 37

List 6 possible characteristics of cancer cells

Answer 37

May have an unusual chromosome number. No need for growth factors to grow/divide May engage in angiogenesis (creation of new blood vessels) No density-dependent inhibition of anchorage dependence Loose attachment to nearby cells Rapidly dividing

Question 38

Is cancer a genetic disease? Why/why not?

Answer 38

Cancer is considered a genetic disease as it arises from a mutation in the cell cycle control system.

Question 39

What is HER2+?

Answer 39

Human epidermal growth factor receptor 2 is a protein that is found in patients in about 20% of breast cancer cases.

Question 40

How does chemotherapy work? Why are there so many side effects?

Answer 40

It targets and is toxic to cells that are rapidly dividing. | This means it can affect cancer cells but also affects other cells that are rapidly dividing, e.g. hair cells.