Brainscape's Knowledge GenomeTM

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


See full index

Genetics I > Gene Expression > Flashcards

Gene Expression Flashcards

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

What is the purpose of transcription?

A

Convert DNA to RNA. First step in protein synthesis

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

What is transcription performed by?

A

RNA polymerase

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

Describe the stages of transcription.

A
  1. Uses DNA template
  2. Ribonucleotides
  3. Produces RNA copies known as transcripts
  4. RNA polymerase binds to regions of DNA called promoters
  5. Transcribes a region before terminating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the subunits of RNA polymerase responsible for?

A

Binding to the promoter. Separating DNA strands. Transcript relocation.

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

What is the promoter region?

A

Contains sequences which are recognised by RNA polymerase.

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

Where are most prokaryotic promoters conserved sequences?

A

2 regions: -10 and -35

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

Where is the start of transcription?

A

+1. Anything before this is negative and referred to as upstream

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

Where is downstream?

A

Anything after +1

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

In prokaryotes what is the sigma factor involved in?

A

Binding to these sequences and recruiting the rest of RNA polymerase enzymes

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

What happens in the Promoter Melting process?

A

DNA strands are separated.

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

Which stranded of DNA is copied?

A

The template strand

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

Which direction does RNA polymerase move in?

A

3’ to 5’ direction with base pairing rules.

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

What is meant by the transcription bubble?

A

Only a short section is single stranded. Transcript only paired a few bases at time.

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

What are the Watson-Crick rules?

A

Complementary base pairing.

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

When does transcription end?

A

Termination signals are encountered and RNA polymerase dissociates

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

What do most prokaryote terminus sequences involve?

A

Inverted repeat structures

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

What happens at the terminus sequence in prokaryotes?

A
  • Region transcribed and RNA formed will create a hairpin structure
  • Causes RNA polymerase to pause and transcript factor is released
  • Another factor there will be an AT rich region which when transcribed will be an AU rich region
  • Will help release as weaker hydrogen bonds than CG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does mRNA do?

A

Codes for proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What do non-coding proteins do?

A

Regulatory. Structural.

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

Describe mRNA

A
  • Protein coding region = open reading frame
  • Start and stop codon
  • Surrounded by untranslated regions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How many proteins do transcripts code?

A

Can code for multiple proteins - typical for genes in same metabolic pathway

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

How can transcripts code for multiple proteins?

A
  • Genes are clustered and therefore transcripts have multiple reading frames
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is meant by polycistronic?

A

Multiple open reading frames and code for multiple proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Why is eukaryotic mRNA more complicated than prokaryotic mRNA?

A

Undergoes specialised processing events at their 5’ and 3’ ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What happens at the 5’ end on eukaryotic mRNA?

A

Modified by addition of 5’cap. Modified base 7-methyguanosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens at the 3’ end on eukaryotic mRNA?

A

Addition of 150-200 adenine nucleotide (polyAtail)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Where does transcription take place?

A

Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What do the modifications of mRNA help with?

A

Ensuring RNA stability, export from nucleus and translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What does mRNA undergo in higher eukaryotes?

A

Splicing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the purpose of translation?

A

RNA to polypeptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How is A U C G translated into amino acid chains?

A

By ribosomes and tRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How is mRNA read?

A

Read in triplets. Each triplet is either a start, stop or an amino acid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the genetic code?

A
  • 64 codons
  • Degenerate
  • Often 3rd base isn’t important
  • Unambiguous
  • Universal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is tRNA?

A

Transfer RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the role of tRNA?

A
  • Amino acids attached to a specific tRNA
  • tRNA with amino acid attached is described as charged
  • Has an anticodon loop, can base pair with a codon through its anticodon
  • 5’ end of codon pairs with the 3’ end of the anticodon
  • Need to have the correct amino acid attached to the tRNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What attaches amino acids to tRNA?

A

tRNA synthetase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Describe the tRNA synthetase.

A

2 binding sites: amino acid and tRNA. Reaction uses ATP, attaches them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the site of protein synthesis?

A

Ribosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Describe a ribosome.

A
  • Composed of RNA and proteins
  • Contains a small and a large subunit
  • Ribosomal RNAs provide the catalytic function for translation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What are the 3 important sites on the ribosome?

A

Aminoacyl site. Peptidyl Site. Exit site.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is the role of Aminoacyl site?

A

Decoding centre. New charged tRNA will enter the ribosome. Anticodon and codon will pair here.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the role of Peptidyl site?

A

Growing polypeptide chain is located

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is the role of Exit site?

A

tRNAs released when no longer needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Where are the A and P site located?

A

Next to each other so peptide bonds can form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is the start codon?

A

AUG

46
Q

What is translation initiation in Prokaryotes?

A
  • Shine Dalgamo sequence which is located upstream of the start codon in the 5’ untranslated region
  • Shine dalgarno is able to pair the 165 ribosomal RNA - small subunit
  • Anchors the mRNA so that the start codon is in the P site
  • Modified version of the methionine is used for the initiating amino acid
47
Q

What is translation initiation in Eukaryotes?

A
  • Small subunit and initiating tRNAiMet binds to the 5’cap

- Then scans the mRNA until the first AUG is reached in the P site

48
Q

Describe the stages of Translation Elongation

A
  1. A ‘charged’ amonacyl tRNA enters the A site pairing codon with anticodon
  2. Elongation factors act as transporters to bring in the aminoacyl tRNA
  3. Peptide bond formation and covalent bond between tRNA and amino acid in P site is broken
  4. Uncharged tRNA at P site
  5. tRNA enters E site, two move to the P site a new one joins at A site (shifts by 3 bases)
  6. Aided by elongation factors
  7. Elongation steps are repeated
  8. Stop codon enters A site - release factors stimulate hydrolysis of the polypeptide from the tRNA
  9. Polypeptide released
49
Q

What is the coding strand?

A

Has the same sequence as the RNA produced

50
Q

What are UTRs?

A

Untranslated regiom - non-coding sequence

51
Q

What is an ORF?

A

Open Reading Frame - part that is translated

52
Q

Where can gene expression be controlled?

A

DNA (transcription initiation). RNA - how stable. Translation - translate or not. Protein- stability.

53
Q

Is RNA more or less stable than DNA?

A

Less

54
Q

What is the key to regulating transcription initation?

A

Regulating the interaction of RNA polymerase with the promoter region.

55
Q

What are regulatory proteins?

A

Transcription factors. Regulate RNA polymerase.

56
Q

What is positive regulation?

A
  • RNA polymerase doesnt have strong affinity for its promoter
  • Needs an activating transcription factor to attract it and turn transcription on
  • Activator proteins need to be able to recognise specific DNA sequences
57
Q

What is negative regulation?

A
  • RNA polymerase is bound to the promoter and is transcribing
  • Gene is expressed unless a repressor protein is present to turn it off
  • Recognises specific sequences
58
Q

How is control of gene expression in prokaryotes special?

A

Can change their gene expression to suit their environmental conditions

59
Q

What do regulatory proteins in prokaryotes do?

A

Respond to changes in environment.

60
Q

What are the 2 forms of regulatory proteins in prokaryotes?

A

One form can bind and regulate gene expression. One form doesn’t. Shape will change.

61
Q

Where is the promoter region of regulatory regions?

A

Upstream. RNA polymerase and activating transcription factor proteins bind

62
Q

What is the operator region?

A

Where repressor transcription factor proteins bind. Blocks RNA polymerase

63
Q

What does the Lac Operon allow for?

A

Allows synthesis of lactose metabolising enzymes in E.coli when lactose is present as a carbon source.

64
Q

What does B galactosidase do?

A

Metabolises lactose

65
Q

What are the structural genes in the Lac Operon?

A

B galactosidase (lacZ). Permease (lacY). Transacetylase (lacA).

66
Q

How is the Lac Operon regulated?

A

Through repressor protein (lacI)

67
Q

What does the LacI gene do on the lac operon?

A

Produces I repressor protein - binds to operator - prevents transcription of lac operon

68
Q

What happens if lactose is present?

A

LacI repressor binds to lactose. LacI changes shape and can’t bind

69
Q

What is allosteric regulation?

A

Regulation of a protein by binding of an effector molecule at a site other than the enzymes active site or DNA binding domain. Causes a conformational change

70
Q

What are the 2 domains of LacI?

A

One for DNA binding. One for lactose.

71
Q

What is the Operator Constitutive?

A

LacI repressor would normally be recognising a sequence of DNA. Doesn’t repress

72
Q

What happens to the lac operon if glucose is present?

A

Glucose is a better carbon source than lactose. If glucose is present the lac genes are not expression. Controlled by the CAP transcription factor.

73
Q

What happens if glucose and lactose are present?

A

Glucose used first - lag phase (lac operon being translated) - then lactose is used

74
Q

How is glucose levels monitored?

A

via cAMP - produced from ATP. cAMP catalysed by adenylate cyclase. Low glucose = cAMP levels increase

75
Q

Describe what happens if glucose is present and the involvement of CAP

A

Glucose - cAMP low - no lactose - no lac mRNA. CAP doesn’t bind (no positive regulation)

76
Q

Where does translation take place?

A

Cytoplasm.

77
Q

What is the difference in translation in eukaryotes and prokaryotes?

A

Eukaryotes = has to move. Prokaryotes = can be translated as soon as its transcribed.

78
Q

Where are ribosomes found?

A

Cytoplas. RER

79
Q

Give an example of when gene expression goes wrong.

A

Drosphilia = legs instead of antennae. Gene which switches off legs in that section doesn’t seem to work

80
Q

What are physical consequences due to?

A

Gene expression - regulatory system rather than the DNA itself

81
Q

How is DNA packaged?

A

Highly ordered - compact. Difficult to transcribe. Different levels.

82
Q

What is chromatin?

A

DNA and proteins. Condensed

83
Q

What is heterochromatin?

A

Dense packagin. Little transcriptional activity.

84
Q

What is Euchromatin?

A

More open, location of most protein coding genes.

85
Q

What is postition effect variegation?

A

Evidence that chromatin packaging can influence gene expression.

86
Q

What is meant by a dynamic structure?

A

Nucleosomes become more spaced out

87
Q

What is in active gene?

A

Regularly spaced nucleosomes

88
Q

What is an active gene?

A

Opening up of chromastin structure so there can be chromatin remodelling.

89
Q

What does the opening up of the chromatin require?

A

Protein complexes that can perform chromatin remodelling

90
Q

What does the opening up of the chromatin allow?

A

Access for RNA polymerase

91
Q

What is the core promoter?

A

RNA polymerase assembles here.
Establishes start site for transcription initiation and includes the TATA box and initiation site
Promoter elements are upstream of the TATA box

92
Q

What are basal promoter elements?

A

Set the basal level of transcription

93
Q

What are the response elements?

A

Allow certain genes to respond to environmental stimuli

94
Q

What are cell specific elements?

A

Located in promoters of genes expressed in only one type of tissue

95
Q

Where can regulatory sites be found?

A

Way upstream or downstream

96
Q

What can increase the level of transcrption?

A

Multiple proteins upstream or downstream to get RNA polymerase to bind. ‘Enhancer’ elements.

97
Q

Describe the multiple binding sites?

A

Some responsible for opening chromatin. Help recruit RNA polymerase. Some cells type specific.

98
Q

What are TERT promoter mutations?

A

The human TERT gene encodes for telomerase reverse transcriptase
Gene is normally transcribed at low levels in most adult differentiated cells
Common mutation in many cancers occurs within the TERT promoter and creates a new binding site for a transcription factor
Result is increased expression of TERT that contributes to cancer cell immortality

99
Q

What is the structure of mRNA?

A

exons and introns

100
Q

What happens to exons?

A

Join together to form the mature mRNA

101
Q

What happens to the introns?

A

non-coding sequences that are removed from the primary transcript

102
Q

Where does splicing occur?

A

In the nucleus at the spliceosome. Formed of RNA and protein.

103
Q

What is Alternative Splicing?

A

Alllows a single gene to produce multiple protein produces. Increasing protein diversity

104
Q

What is RNA localisation?

A

Where to gove

105
Q

What can determine where splicing occurs?

A

Regulatory proteins

106
Q

What is a missense mutation?

A

Mutation that results in an amino acid change but does not change the reading frame of the protein

107
Q

What is a silent mutation?

A

A mutation that does not result in a change in amino acid

108
Q

What is a frameshift mutation?

A

A mutation involving insertion or deletion of bases that is not a multiple of 3. This shifts the reading frame in all codons following the site of mutation

109
Q

What is a nonsense mutation?

A

A mutation that changes a codon specifying an amino acid into a stop/termination codon

110
Q

What are loss of function mutations?

A

Usually recessive and involve either complete loss or reduction in protein function

111
Q

What are gain of function mutations?

A

Usually dominant and involve either an increase in protein function, acquisition of new function oor acquiring the ability to interfere with the function of the wild-type protein.

Genetics I (5 decks)

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