Gene Expression 1 (Genetics 5)

Question 1

Control elements

Answer 1

non-coding DNA segments that regulate transcription by binding transcription factors

Question 2

Promoters

Answer 2

sequences of DNA bound by the first component

Question 3

Enhancers

Answer 3

short nucleotide sequences that influence the rate of transcription, could be thousands of nucleotides away from the promoter, could also be bound by silencers/ repressor proteins

Question 4

Introns

Answer 4

non-coding

Question 5

Transcription

Answer 5

The process by which the information in a strand of DNA is copied into a new molecule of mRNA

Question 6

Where does Transcription take place?

Answer 6

within the nucleus, Mature mRNA is exported to the cytoplasm for translation

Question 7

What are the 4 steps of transcription

Answer 7

Initiation, Elongation, Termination and processing

Question 8

Initiation

Answer 8

unwinding of DNA, RNA polymerase binds to the template strand

Question 9

Elongation

Answer 9

RNA polymerase moves along the temperature strand, synthesising the pre-mRNA molecules

Question 10

Termination

Answer 10

addition of additional adenine nucleotides at the 3’ of the RNA transcript (polyadenylation)

Question 11

Processing

Answer 11

Introns are removed and the exons are spliced together to form a mature mRNA molecule consisting of a single protein-coding experience

Question 12

What is the purpose of Chromatin remodelling?

Answer 12

Exposes the Promoter

Question 13

Initiation: Recognition

Answer 13

Pre-initiation complex binds to
recognition sites within the promoter
» Control elements facilitate the binding
of the complex components
* Remember that distal control
elements can be far upstream but 3D
folding can bring them physically
closer
» Transcription occurs within a
transcription bubble opened by the
polymerase which has multiple
functions

Question 14

Mediator Complex

Answer 14

Made up of many proteins in head, middle and tail regions, it interacts with transcription factors and RNA polymerase II

Question 15

TATAA box

Answer 15

a recognition site within the
promoter with the nucleotide sequence TATAA.

Question 16

PreInitiation Complex (PIC)

Answer 16

General Transcription Factors + RNA Polymerase

Question 17

Anti-Sense Strand

Answer 17

non-coding DNA strand

Question 18

Sense Strand

Answer 18

Coding strand, carries the translatable information

Question 19

Pre-mRNA processing

Answer 19

both ends of pre mRNA are modified by the addition of chemical groups, introns are removed and exons are spliced together

Question 20

What is capping

Answer 20

As RNA polymerase is elongating the
transcript, guanyltransferase attaches a
methylated GTP cap to the 5’ end of the
mRNA

Question 21

What are the purposes of capping

Answer 21

1. Regulation of nuclear export
2. Prevention of degradation by exonucleases
3. Promotion of translation
4. Promotion of 5′ proximal intron excision.

Question 22

Splicing

Answer 22

introns must be removed to get mature mRNA

Question 23

How are introns removed?

Answer 23

a complex of RNAs and proteins called the spliceosome

Question 24

Poly-A-Polymerase

Answer 24

Adds about 100-250 Adenine nucleotides to the cut end forming a Poly-A-Tail

Question 25

Termination

Answer 25

Has a different mechanism for each polymerase

Question 26

Cleavage

Answer 26

A reaction that severs one of the covalent sugar-phosphate linkages between NUCLEOTIDES that compose the sugar phosphate backbone of DNA.

Question 27

What does RNA polymerase I produce?

Answer 27

rRNA

Question 28

What does RNA polymerase II produce?

Answer 28

mRNA

Question 29

What does RNA polymerase III produce?

Answer 29

tRNA

Question 30

What does mitochondrial RNA polymerase produce?

Answer 30

all mitochondrial RNA

Question 31

What part of the template strand does RNA polymerase bind to?

Answer 31

The promoter region

Question 32

How is the pre-initiation complex formed?

Answer 32

TBP binds to the TATTA box found in the promotor region
TFIID recruits TFIIA and TFIIB, TFIIB recruits TFIIF which then recruits TFIIE and TFIIH

Question 33

What is RNA polymerase ii made out of?

Answer 33

A complex of 12 protein subunits which act as
* Helicase
* Sliding clamp
* Single-stranded DNA binding protein etc.

Question 34

What is the benefit of a poly-A-tail?

Answer 34

The tail stabilises the transcript, aids in transcription termination and exportation from the nucleus to the cytosol