WEEK 5

Question 1

What is the phenotype of an organism?

Answer 1

The characteristics an organism has (eg. height, weight, blood group etc)

Question 2

What is the genotype of an organism?

Answer 2

The combination of genes inherited from parents

Question 3

What two factors influence the phenotype of an organism?

Answer 3

The genotype and the environment (eg. infectious agents, toxins, diet etc)

Question 4

What are ‘housekeeping genes’?

Answer 4

A set of structural genes constitutively expressed in all cell types coding for proteins found in all cells

Question 5

What causes different cell-types to express different proteins?

Answer 5

Turning on/off certain genes

Question 6

Detail the regulation of gene expression with regards to the pathway of DNA to protein

Answer 6

DNA-(transcription control)->RNA transcript-(RNA processing control)->mRNA-(RNA transport and localisation control)->mRNA-(mRNA degradation control/translation control)->inactive mRNA/Protein-(protein activity control)->inactive protein

Question 7

What is a gene composed of?

Answer 7

structural information coding for a protein and regulatory sequences giving instructions for expression

Question 8

What are gene promoters?

Answer 8

5′ (upstream) regulatory sequences which control transcription initiation

Question 9

What is the role of general transcription factors?

Answer 9

Recognise and bind to the gene promotor, recruit RNA polymerase II, allow ‘basal’ level of transcription

Question 10

What are gene enhancers?

Answer 10

Regulatory sequences found upstream and downstream of the gene which control the rate of transcription

Question 11

What is the role of gene-specific transcription factors?

Answer 11

TFs that bind to enhancers and cause increased transcription

Question 12

What is the difference between a gene promoter and enhancer?

Answer 12

Promoter initiates transcription, enhancer enhances transcription

Question 13

How far are enhancers and promoters located from the gene?

Answer 13

Enhancer is much further from the gene than the promoter, which needs to be close

Question 14

What is the nucleosome composed of?

Answer 14

8 histones (2x H2A, H2B, H3 and H4)

Question 15

What are histone tails subject to?

Answer 15

Chemical modifications which act as regulatory information

Question 16

What is the ‘histone code’?

Answer 16

Layer of information overlapping the DNA, involved in turning genes on/off

Question 17

What is responsible for histone tail modification?

Answer 17

Enzyme families (eg. histone acetyl transferases=acetyl addition on lysine residues, histone de-acetylases=acetyl removal from lysine residues)

Question 18

How does the environmental factors (eg. diet) and therapeutic drugs affect histone tail modification?

Answer 18

Can cause enzyme inhibition

Question 19

Increased methylation:

opposite occurs for decreased methylation

Answer 19

attracts proteins which condense the DNA-histone complex, so TFs less able to bind (gene inhibition)

Question 20

Decreased acetylation:

opposite occurs for increased acetylation

Answer 20

increases +ve charge on histone, increases attraction to phosphate (PO4-) groups on DNA, condenses DNA-histone complex, so TFs less able to bind (gene inhibition)

Question 21

What is an example of epigenetic heritability?

Answer 21

X-linked inactivation in female mammals (one X c’some is inactivated to ensure equal gene expression levels (dosage compensation)-inactive state passed on)