BM210

Question 1

Describe transcription factors

Answer 1

A sequence specific DNA binding protein which helps regulate transcription initiation

Question 2

Where are missense mutations found within the gene?

Answer 2

Exon regions

Question 3

In which region of the gene is there an enrichment of CpG islands?

Answer 3

Promotor region

Question 4

Describe epigenetics and give an example

Answer 4

Modifications to the genome that affect gene expression but do not alter the DNA sequence

eg: DNA methylation

Question 5

Describe DNA methylation

Answer 5

The addition of methyl groups to nitrogen bases of nucleotides (mainly cytosine).

DNA methylation regulates gene expression by gene silencing, by inhibiting the binding of transcription factors to DNA or recruiting proteins involved in gene repression.

Question 6

What role do CpG islands play in gene expression?

Answer 6

CpG islands undergo chemical modifications which alter binding of transcription factors

Question 7

Which enzyme methylates the cytosine in CpG islands?

Answer 7

DNMT (DNA Methyltransferase)

Question 8

Describe the 2 chromatin states

Answer 8

Euchromatin: Loosely packed, enriched in genes

Heterochromatin: Tightly packed,
genetically inactive

Question 9

What is the start and end sequence of all introns?

Answer 9

Begin with GU and end with AG

Question 10

Describe alternative splicing?

Answer 10

A process where different mRNAs are generated from the same primary transcript, thereby generating proteins with different functions

Question 11

Describe the 2 mechanisms of cell communication

Answer 11

Intercellular signalling:
- Communication between cells
- Eg: synaptic transmission

Intracellular signalling:
- Signalling within the cell
- Eg: generation of second messengers

Question 12

Describe autocrine signalling and give an example?

Answer 12

Cell targets itself, synthesising a soluble ligand that is then released
Eg: Il2

Question 13

Describe paracrine signalling and give an example?

Answer 13

Cell targets nearby cells, generating a signal resulting in a mediator being released.
Eg: the release of chemokines by neutrophils, which attract other cells by chemotaxis

Question 14

Describe endocrine signalling and give an example?

Answer 14

Hormone dependent mechanism where the signalling cell targets a distant cell through the bloodstream.
Eg: the liver is an endocrine gland due to the secretion of insulin

Question 15

Describe the bonding present in Starch

Answer 15

Amylose - Alpha 1,4 glycosidic (Unbranched)

Amylopectin - Alpha 1,4 with Alpha 1,6 branches (tightly packed)

Question 16

Describe the bonding in glycogen

Answer 16

Alpha 1,4 glycosidic bond with lots of Alpha 1,6 branches (compact)

Question 17

Describe the bonding in cellulose

Answer 17

Beta 1,4 glycosidic bond (unbranched, straight fibrous chain)

Question 18

Describe the gene to protein formation

Answer 18

1. Enzymes break H bonds between bases, unwinding the helix
2. RNA polymerase builds a complimentary strand of mRNA using nucleotides from the nucleus
3. The mRNA template leaves nucleus to ribosome
4. tRNA transports amino acids to ribosome
5. Peptide bonds form between amino acids to form poly peptide chain

Question 19

What are the key steps involved in the activation of PKB in target cells by insulin?

Answer 19

Insulin binds to its receptor (IR) which is a tyrosine kinase, this leads to receptor auto-phosphorylation.

The phosphorylated insulin receptor acts as a docking site for insulin receptor substrate proteins (IRS).

The receptor phosphorylates IRS, which then recruits the lipid kinase, phosphoinositide 3-kinase, which converts PIP2 to PIP3.

Binding to PIP3 activates PDK1, which then phosphorylates and activates PKB.

Question 20

Explain GLUT4 and which type of transport it is?

Answer 20

A carrier protein which transports glucose, through facilitated diffusion which is passive transport

when insulin is present, glut4 inserts into fat and muscle cells

glucose then binds to glut4 which results in conformation shape of carrier protein

glucose is released inside cell

Question 21

Describe the function of histone proteins

Answer 21

Histones are highly basic proteins which are positively charged, this allows them to associate with DNA which is negatively charged. DNA wraps around histone proteins in order for it to condense and package correctly within the nucleus.

Question 22

Name 2 second messengers?

Answer 22

cAMP and Ca2+