Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology HL IB 2020-22 > 7.2 Transcription and gene expression (HL) > Flashcards

7.2 Transcription and gene expression (HL) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What are promoters?

A

Non-coding sequence/ region of DNA responsible for initiation of transcription

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

How do promoters help production of polypeptides?

A

They act as binding sites for RNA polymerase, which is responsible for formation of covalent bonds between nucleotides that synthesize RNA/mRNA for polypeptides.

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

How is binding of RNA polymerase to promoter mediated?

A

Controlled by multiple transcription factors in eukaryotes

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

What are operators?

A

They also regulate transcription however usually through inhibition

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

What are repressors?

A

Proteins that bind to operators to prevent RNA polymerase from transcribing

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

In a lac operon, does the lactose need to be broken down or made and why?

A

When lactose is present, enzymes need to be made to break it down to provide energy for the prokaryote.

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

How does a lac operon work?

A
  • Lactose binds to the repressor
  • Repressor cannot bind to the operator
  • RNA polymerase binds to the promoter allowing genes that produce proteins to be transcribed
  • mRNA is used to make enzyme to break down lactose after which repressor is free and it will bind to the operator again
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does transcription need to be inhibited in a lac operon?

A

If lactose is not present, there is no need to transcribe enzymes for it. Hence, it is more energy efficient for the prokaryote

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

Similarities and differences between gene expression in prokaryotes and eukaryotes

A

They both have promoters however eukaryotes don’t have operators. Instead they have enhancers and silencers

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

What is an enhancer?

A

Coding sequence that binds to activator proteins to increase rate of transcription

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

What is a silencer?

A

Coding sequence that can bind to repressor proteins to block or reduce rate of transcription

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

How can environment of an organism impact gene expression?

A

Exposure to pathogens, chemicals, toxic materials. Hair and skin color can be affected by sunlight and temperatures.

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

What is a morphogen?

A

Chemical that affects gene expression by regulating transcription factors

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

How does environment affect fur pigmentation in Himalayan rabbits?

A

Gene C controls pigmentation. It is active when temp is between 15-25C. At higher temp, it is inactive so fur will be white as no pigment is produced. In colder weather, the rabbit’s colder extremities (feet, nose, ears) produce a black pigment

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

What are specific examples of environmental impact on gene expression?

A
  • Changing of flower color due to pH of soil

- Animals changing sex in response to social cues

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

What are the 3 regions of the gene

A

The promoter (where transcription is initiated), the coding region (region transcribed) and the terminator (where transcription ends).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How would you describe the concentration of morphogens in embryonic cells?

A

They contain uneven concentrations which results in activation and inhibition of different genes in different cells and hence why we are unique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a nucleosome made of?

A
  • Histone H1
  • DNA coils
  • Octamer of histones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What part of nucleosome is exposed and what does this allow?

A

Tail of histone is usually exposed which allows it to be easily modified

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

2 chemical groups that affect transcription regulation

A

Acetyl and methyl group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Does methylation of histones promote or inhibit transcription?

A

Direct methylation usually inhibits however it can either promote or inhibit depending on location in genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What can DNA methylation be affected by?

A

They can be associated with age, diet, environmental conditions or exposure to infectious agents

23
Q

How are euchromatin and heterochromatin made?

A
  • Heterochromatin is when DNA is bound more tightly to the histone to inhibit transcription making it less accessible
  • Euchromatin is when DNA is loosened to make it more accessible to transcription factors
24
Q

What are the types of methylation?

A

Hypermethylation is when genes are unable to express completely while hypomethylation is when a lot of genes are being transcribed and expressed

25
Q

Why will twins show different levels of methylation?

A

They will have different experiences and environment stimuli which will cause different levels of methylation in different chromosomes

26
Q

Why do cells become more specialized as they age?

A

As cells age, they have gone through acetylation and methylation so there is more inhibited and promoted DNA

27
Q

What is acetylation?

A

It is addition or removal of acetyl groups from the histone

28
Q

Outline the process of acetylation on lysine of histone tails

A
  • Lysine usually bears a positive charge which binds to negatively charged DNA to form condensed structure, inhibiting transcription
  • Histone acetylation neutralizes positive charge so structure is less condensed= more transcription
29
Q

What is epigenetics?

A

It is the study of heritable changes in organisms that are brought about by changes in gene expression as opposed to modification of genetic code

30
Q

How can modified histones get inherited by offspring?

A

As not all epigenetics get erased (usually 1% remains), some can get passed down to offspring during cell division

31
Q

What are epigenetic tags?

A

Markers that acetylation and methylation used to mark DNA to control transcription.

32
Q

Epigenome

A

Sum of epigenetic tags

33
Q

Does methylation of DNA change in replication or get copied?

A

It gets copied

34
Q

Why do new zygotes not inherit all epigenetic tags?

A

They get erased because babies need unmarked DNA so cells can differentiate into specialized cell types

35
Q

Give examples of how inheritance and creation of epigenetic tags can be influenced at different stages in life

A
  • Fertilization: Some imprinted genes are not erased
  • Pregnancy: Maternal diet
  • Infancy: Early exposure to bacterial microbes
  • Young adult: Diet, lifestyle
  • Senior: Age related changes
36
Q

Why dont prokaryotes have pre-mRNA as opposed to eukaryotes?

A

Prokaryotes don’t have a nucleus so they combine transcription and translation. Eukaryotes require post-transcription modification (removal of introns) so immediate product is pre-mRNA and after splicing, it is mature mRNA `

37
Q

What were introns referred to as previously?

A

‘Junk’ DNA

38
Q

What direction does transcription occur in and through which parts?

A

5’ to 3’ direction. 5’ end/ phosphate of RNA nucleotide is added to 3’ end of growing mRNA

39
Q

What is covalently bonded in transcription?

A

Ribonucleoside triphosphates

40
Q

What are introns?

A

Non-coding region of the gene that doesn’t express but plays a role in transcription initiation

41
Q

What are exons?

A

Part of the mRNA which expresses genes

42
Q

What is a spliceosome?

A

Complex made of smaller mRNA and proteins that removes introns and causes it to form a loop while allowing exons to be joined

43
Q

What can introns do after being removed?

A

They will be broken down and used to form nucleotides

44
Q

What is mature mRNA?

A

It contains only exons and leaves nucleus to be translated into polypeptides

45
Q

What is alternative splicing?

A

Removal of exons from the mRNA

46
Q

What does mature mRNA consist of on both ends?

A

It will have a poly A tail (100-200 adenines) on 3’ end and it will be capped on the 5’ end by a methyl group

47
Q

Purpose of capping mature mRNA

A

Prevents degradation of mRNA and allows it to be recognized

48
Q

Purpose of poly A tail

A

Improves stability and facilitates export

49
Q

What does alternative splicing imply for a gene?

A

They can have varying biological functions as different proteins can be made

50
Q

What is a protein family that is commonly alternatively spliced?

A

Immunoglobulin

51
Q

What happens after enhancer or silencer is activated?

A

DNA will start to bend using DNA bending protein and enhancer/silencer will be on top of promoter. According to their function, this can either attract or prevent transcription factors and hence affect the calling for RNA polymerase

52
Q

What is a distal control element?

A

Includes enhancers and silencers but are distant from promoter

53
Q

What is a proximal control element?

A

Nearer to promoter and binding is necessary to initiate transcription

Biology HL IB 2020-22 (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions