Gene organisation and transcription I

Question 1

What is a gene?

Answer 1

Functional unit of DNA

Encodes information for making proteins and functional RNAs

Question 2

What does the human genome consist of?

Answer 2

22 pairs of autosomal chromosomes

1 pair of sex chromosomes

Question 3

Give an example of genes expressed in all cells

Answer 3

Housekeeping genes

Question 4

Transcription

Answer 4

process of nucleotide information in DNA being copied into RNA

Question 5

3 steps of transcription

Answer 5

DNA strands unwind
Ribonucleotide base pair with DNA bases on 1 strand
Ribonucleotide bases joined by phosphodiester bonds in 5’ to 3’ direction

Question 6

Which strand of DNA is transcribed?

Answer 6

Anti-sense

it is anti-sense to the mRNA produced

Question 7

What are the roles of the 3 types of RNA polymerase?

Answer 7

I – transcribes rRNA genes
II – transcribes genes encoding proteins into mRNA
III – transcribes tRNA and 5S RNA genes

Question 8

Transcription factors

Answer 8

Special gene regulatory factors
Regulate levels of transcription
Either activator or repressor

Question 9

Transcription activators

Answer 9

Activate gene expression

Question 10

Transcriptional repressors

Answer 10

Suppress gene expression

Question 11

What requires an initiation step and why?

Answer 11

Elongation reaction of RNA synthesis

To build a transcription complex

Question 12

Gene promotor

Answer 12

DNA complex at which initiation complex assembles

Question 13

TATA DNA sequence

Answer 13

Specifies initiation point for transcription, after which RNA polymerase II will begin transcription

Question 14

Basal transcription complex

Answer 14

Allows RNA polymerase II to be phosphorylated and engage in transcription

Question 15

What constitutes the basal transcription complex?

Answer 15

TFII (D, A, B, F, E, H, J)
and
RNA polymerase II

Question 16

How does the basal transcription complex form?

Answer 16

TF II D binds to TATA, partially unwinding DNA asymmetrically so transcription is unidirectional
TF II A and TF II B bind
RNA polymerase II and TF II F bind to TF II B
TF II E, TF II H and TF II J bind to RNA polymerase II

Question 17

What does TF II H promote?

Answer 17

further unwinding of DNA helix

to facilitate RNA synthesis by RNA polymerase II

Question 18

What do transcription factors bind to?

Answer 18

Transcription factor binding sites

Bend DNA

Question 19

How do transcription factors facilitate transcription?

Answer 19

Help remodel chromatin by recruiting proteins with enzymatic activity that modify histones

Question 20

Hyperacetylation of histones

Answer 20

Gene expression

Question 21

Hypoacetylation of histones

Answer 21

Gene repression

Question 22

What factors determine TF expression?

Answer 22

Cell lineage

Signals outside cell (hormones, growth factors)

Question 23

What may arise if TFs are mutated?

Answer 23

Genetic disorders

Cancer

Question 24

Give 2 examples of cancers which arise from mutated TFs

Answer 24

Leukaemia
Breast cancer (over expression of oestrogen receptor)