18.01.04 Gene structure Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is a gene?

A

Region of coding DNA either for:
mRNA encoding for a functional polypeptide chain or
a functional RNA molecule (ncRNa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the sequence of the start codon?

A

AUG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the sequence of the stop codon.

A

TAA
TAG
TGA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Give three examples of cis-acting transcriptional regulatory DNA element.

A

1) Promoter
2) Enhancers
3) Silencers
4) Insulators

All contains recognition sites for trans-acting DNA-binding TFs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the structure of the promoter?

A

Core promoter and nearby regulatory elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where is the core promoter located? Describe some of its features

A

Located at 5’ end of the gene
Docking site for transcriptional machinery
Defines transcription start site
Defines direction of transcription (sense/antisense)
Contains the TATA box

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the TATA box.

A

Conserved 8bp sequence - TATA(T/A)A(T/A)N
Binding site for TATA-box-binding protein subunit of RNA polymerase II transcription factor
Reversal of sequence (seen in some mutations) will remove its ability to promote transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Name three other regulatory elements associated with the promoter.

A

1) Initiator element
2) Downstream promoter element (DPE)
3) Downstream core element (DCE)
4) RNA polymerase II transcription factor-recognition element
5) Motif ten element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe proximal promoter elements

A

Immediately upstream of core promoter
Works synergistically
Contains multiple binding sites for activators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the role of enhancers.

A

Typically long-distance transcriptional control elements that can be situated distally from the promoter.

Regulates transcription in spatial or temporal way
Functions independently of the distance and orientation of the promoter
Functionally similar to PPEs
Often associated with genes that are abundantly expressed e.g. IG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the role of silencers.

A

1) Sequence-specific elements that confer a negative effect on transcription of target gene.
2) Functions independently of the distance and orientation of the promoter
3) Can be situated as part of the proximal promoter,distal enhancer or further away.
4) Can be located in and intron or 3’UTR
5) Can act synergistically with negative TFs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the role of insulators.

A

Can block genes from being affected by the transcriptional activity of neighbouring genes. Two main properties:

1) Block enhancer-promoter communication
2) Prevents the spread of repressive chromatin

Usually 0.5-3kb in length. Functions independently of the distance and orientation of the promoter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe some features of the 5’UTR.

A

1) Binds ribosome for translation
2) Usually ~100-200nt
3) High GC content
4) 10-18% express alternative 5’UTRs by using multiple promoters for regulation of gene expression
e. g. BRCA1 has two different transcripts relating to two different promoters and therefore have 5’UTR differences. Longer transcript predominantly expressed in breast cancer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe some features of the 3’UTR.

A

1) Contains a terminator sequence for RNA polymerase release
2) Regulatory elements in this region can influence mRNA polyadenylation, translation efficiency, localiation and stability.
3) Contains primary signal for the polyadenylation signal (AATAAA/AAUAAA)
4) PolyA tail added to mRNA transcript to control nuclear export, translation and stability of mRNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Name a disease associated with mutations in the core promoter?

A

B-Thalassemia - mutation in TATA box

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Name two diseases associated with mutations in the proximal promoter.

A

FH - promoter variants reported in LDLR

CMT - mutation in connexin 32 promoter

17
Q

Name a disease associated with mutations to an enhancer.

A

X-linked deafness. 900kb deletion upstream of POU3F4 gene.

18
Q

Name a disease associated with mutations to a silencer.

A

FSHD - deletion of D4Z4 repeats

19
Q

Name a disease associated with mutations to an insulator.

A

Beckwith-Wiedemann syndrome. CTCF binding site of H19/Igf