Paper 2 - Mutations, Regulations Of Protein Synthesis And Cancer

Question 1

Define stem cell

Question 2

Explain the characteristics of totipotent cells

Answer 2

A stem cell that can develop into any type of body cell - found in the embryos

Question 3

Pluripotent cells

Answer 3

Cells that can differentiate into any body cell except for placenta cells - found in the embryo

Question 4

Multipotent cells

Answer 4

Cells that can divide to form only a limited number of different cell types - found in mature mammals

Question 5

Unipotent cells

Answer 5

Cells that can only divide to form a single type of cell - found in mature mammals

Question 6

Explain what a transcription factor is

Answer 6

A protein molecule that binds to the promotor region of a gene and controls transcription of the gene. It can either stimulate transcription (activator) or inhibit transcription (repressor)

Question 7

Explain the role of oestrogen in the regulation of transcription in genes

Answer 7

1. Oestrogen is a lipid soluble hormone that enters target cells by simple diffusion
2. Target cells have complementary oestrogen receptors that oestrogen binds to = oestrogen-oestrogen receptor complex
3. This complex is an activated transcription factor and enters the nucleus
4. The complex binds to specific promotor regions of DNA and helps RNA polymerase to bind
5. This stimulates transcription of the gene

Question 8

What are epigenetic markers ?

Answer 8

Chemical tags that can attach to the DNA and make chromatic either more/less condensed

Question 9

Define a protooncogene

Answer 9

A gene that produces a protein that stimulates cell division

Question 10

Define tumour suppressor gene

Answer 10

A gene that produces a protein to inhibit cell division

Question 11

SiRNA

Answer 11

1. SiRNA binds to a complex of proteins and an enzyme and becomes single stranded
2. This complex binds to an mRNA strand by complimentary base pairing
3. The enzyme cuts up mRNA into smaller fragments
4. The mRNA cannot be translated so a protein cannot be made

Question 12

Methylation of DNA

Answer 12

1. More methyl groups are attached to DNA = chromatin is more condensed
2. This prevents transcription factors from binding to the promotor region of a gene
3. This makes it harder for RNA polymerase to bind and transcribe DNA
4. Rate of transcription is reduced

Question 13

Deacetylation of histones

Answer 13

Enzyme HDAC removes acteyl groups from histones

1. Acetyl groups are removed from histones = chromatin more condensed
2. This prevents transcription factors from binding to the promotor region
3. Harder for RNA polymerase to bind to the promotor region and transcribe DNA
4. Rate of transcription is reduced and gene isn’t expressed

Question 14

What’s a vector?

Answer 14

Something that is used to transfer DNA into a cell e.g, a plasmid