Genetics Lecture 4 Flashcards Preview

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Flashcards in Genetics Lecture 4 Deck (29)
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1
Q

Does RNA polymerase require a template?

A

No.

2
Q

During transcription, what unwinds the DNA?

A

RNA polymerase has helicase activity.

3
Q

Define the promoter region for transcription initiation. Where is it found?

A

Site where RNA polymerase attaches. Immediately precedes the transcription initiation site, upstream of the gene.

4
Q

The first site of transcription begins with +1. Where is the promoter region found?

A

Negative region.

5
Q

What 3 things collectively make a gene?

A

The promoter, the RNA coding sequence, and the terminator.

6
Q

What direction does RNA polymerase transcribe?

A

5’ to 3’.

7
Q

Describe the prokaryotic promoter region, including where they are found and the sequence.

A

Has 2 conserved regions:
At -35 - TTGACA
At -10 - TATAAT

8
Q

In prokaryotes, how does RNA polymerase attach to the promoter region?

A

A polypeptide called sigma factor binds to the two promoter regions, RNA polymerase binds at -55 to +20. Holoenzyme untwists the DNA at -10, and the sigma factor dissociates.

9
Q

When RNA polymerase is bound to the DNA, where is the DNA untwisted, and by what? What is it called before and after holoenzyme action?

A

At -10 region by holoenzyme.

Closed promoter complex before untwisting, and opened promoter complex after.

10
Q

As RNA polymerase moves forward transcribing, does the RNA remain bound to the DNA or does it dissociate?

A

Dissociates as RNA polymerase moves.

11
Q

Which is faster, DNA polymerase or RNA polymerase, and why?

A

RNA polymerase is slower as it proofreads as it moves forward.

12
Q

How many kinds of RNA polymerases are in prokaryotes vs eukaryotes?

A

Prokaryotes have one, eukaryotes have three.

13
Q

What are snRNA?

A

Small nuclear RNA, that binds to some enzymes like telomerases.

14
Q

What type of RNA makes up the most?

A

rRNA.

15
Q

Which eukaryotic RNA polymerase transcribes mRNA?

A

RNA polymerase 2.

16
Q

Where is the core promoter in eukaryotes? What is it called, and what kind of sequence is it?

A

Within 50bp upstream of +1. An initiator sequence called Inr, and has a TATA box.

17
Q

Eukaryotic promoter regions have an additional 2 boxes in addition to the one found in the core promoter. Where are the two found, what are they called, and what sequence are they?

A

Promoter-proximal elements
CAAT box at -75
GGGCGG at -90

18
Q

What mediates binding of RNA polymerase in eukaryotes?

A

Transcription factors.

19
Q

How many copies of mRNA are made, just one or many?

A

Many.

20
Q

How is transcription terminated in prokaryotes?

A

Stops as soon as the RNA polymerase reaches the termination sequence.

21
Q

How is transcription terminated in eukaryotes?

A

Transcription continues for an additional 30bp. Is a special sequence that induces a termination hairpin formation, dissociating RNA polymerase.

22
Q

Which of the two, eukaryotes and prokaryotes, have pre-mRNA?

A

Just eukaryotes.

23
Q

What does pre-mRNA have at the polar ends that mature mRNA doesnt have? Why is it present?

A

An untranslated region that acts as a buffer, and later modifed to protect the mRNA from exonucleases.

24
Q

What happens to the 5’ end of pre-mRNA? Whats unusual about it, and what does this facilitate?

A

A capping enzyme adds 2 methylated guanine molecules, an unusual 5’ to 5’ bond, which exonucleases cant break.
Facilitates ribosomal binding.

25
Q

What happens to the 3’ end of pre-mRNA? What does this facilitate and inhibit?

A

A polyA tail of 50-250 adenine molecules are added.

Inhibits degradation, and facilitates export from the nucleus.

26
Q

What do introns begin and end with that allows then to be spliced?

A

Begin with GU, and end with AG.

27
Q

What mediates splicing, and what are they? How many are there? Name them.

A

Small nuclear ribonucleoprotein particles - SnURPs. Are snRNA associated with proteins.
Are 5 of them
U1, U2, U4, U5, U6.

28
Q

Describe how splicing is carried out.

A

The SNURPs U1 and U2 recognise the GU and AG of introns and bind to them
The other 3 SNURPs bring the U1 and U2 together. The strands are then joined together.

29
Q

Can translation occur at the same time as transcription in prokaryotes and eukaryotes?

A

Yes in prokaryotes only.

In eukaryotes, it must finish transcription, be exported, and spliced first.