7.2 Transcription and Gene expression (HL) Flashcards

1
Q

What are the 3 main parts of transcribed RNA?

A

Promoter
Coding sequence
Terminator

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2
Q

What is the function of the promoter?

A

Non-coding sequence responsible for initiation if transcription

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3
Q

What binds the the promoter?

A

RNA polymerase

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4
Q

What controls the binding of RNA polymerase to the promoter?

A

Transcription factors

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5
Q

What are the two types of transcription factors?

A

Proximal or distal

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6
Q

What is the function of the coding sequence?

A

To code for proteins

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7
Q

What is the function of the terminator?

A

To stop RNA polymerase from continuing to transcribe

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8
Q

Which strand is the antisense strand?

A

The strand that is transcribed into RNA

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9
Q

Which strand is the sense strand?

A

The strand that is not transcribed into RNA

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10
Q

What is another name for the antisense strand?

A

Template strand

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11
Q

In which direction is the sense strand?

A

It is gene specific as either strand could have a gene

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12
Q

What is transcription?

A

The process by which DNA sequence (gene) is copied into complementary RNA sequence

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13
Q

What enzyme carries out transcription?

A

RNA Polymerase

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14
Q

Describe the process of transcription

A

RNA pol covalently binds nucleotide triphosphates (releasing 2 phosphates)
The 5’ phosphate links to the 3’-end

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15
Q

In what direction does transcription occur?

A

5’ - 3’

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16
Q

What must happen to the RNA sequence post-transcriptionally in eukaryotes?

A

Modification to the RNA sequence

17
Q

Define capping

A

Involves adding a methyl group to the 5’ end of RNA

18
Q

Why does capping occur?

A

To protect against degradation by exonucleases
Also used for recognition

19
Q

What are the 3 post-transcriptional events that occur to form mature mRNA?

A

Capping
Polyadenylation
Splicing

20
Q

Define polyadenylation

A

Adding a long chain of adenine nucleotides (poly-A tail) to the 3’ end of the transcript

21
Q

Why does polyadenylation occur?

A

Improves transcript stability and facilitates the export from the nucleus

22
Q

Define splicing

A

The removal of introns from RNA

23
Q

Why does splicing occur?

A

Introns do not code for proteins

24
Q

Define alternative splicing

A

The removal of exons that will result in the formation of different polypeptides from a single gene sequence

25
What are the functions of the regulatory proteins?
Bind to DNA sequences outside of the promoter and interact with transcription factors
26
Where do activator proteins bind?
Enhancer site
27
What is the function of activator proteins?
Increase rates of transcription
28
Where do repressor proteins bind?
Silencer sequences
29
What is the function of repressor proteins?
Decrease rates of transcription
30
What can cause changes in gene expression?
A variety of external and internal factors such as chemical signals
31
What determines how tightly DNA is packaged?
The protruding tails on histone
32
What can make DNA coil less tightly on a histone?
Adding an acetyl group to the tail, neutralising the charge on the histone
33
Why would we want DNA to coil less tightly?
Ease of transcription
34
What can make DNA coil more tightly on a histone?
Adding a methyl group to the tail, maintaining the positive charge
35
Define heterochromatin
DNA which is supercoiled and not accessible for transcription
36
Define euchromatin
DNA which is loosely packed and therefore accessible to the transcription machinery
37
What effect will increased methylation have on gene expression?
Decrease gene expression (by preventing the binding of transcription factors)
38
Define epigenetics
The study of changes in phenotype as a result of variations in gene expression levels
39
What factors (other than genes) can effect epigenetics?
Environmental factors E.g.: Pathogens, diet, exposure