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MCB 1 > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

Name of bond that links Sugar to Base

A

B-N-Glycosidic Bond

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2
Q

Primary Structure of Nucleic Acids

A

Linear chains of interconnected Nucleotides forming a backbone
(Phosphodiester bond)

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3
Q

Secondary Structure of Nucleic Acids

A

Double helix where base pairing occurs between 2 strands and H-Bond linkage

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4
Q

A-DNA

A
  • Right Handed
  • 2.6nm diameter
  • 11 Bp/turn
  • Anti conf.
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5
Q

B-DNA

A

MOST COMMON
- Right handed
- 2.0nm diameter
- 10 Bp/turn
- Anti conf.

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6
Q

Z-DNA

A
  • Left handed
  • 1.8nm diameter
  • 12 Bp/turn
  • Pyr: Anti , Pur: Syn
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7
Q

Tautomers

A

Isomers differing in position of Proton or Electron
- Oxo-Enol
- Amino-Imino

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8
Q

What are the physiologically preferred Tautomer forms of Bases

A

Oxo (=o) & Amino (NH2)

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9
Q

2 Types of Heterochromatin

A
  • Facultative: Can become Euchromatin
  • Constitutive: Perm. condensed
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10
Q

DNA Condensation forms

A

1) DNA Double Helix (2nm)
2) Beads on a String (11nm)
3) Solenoid Coil (30nm)
4) Radial Loop (300nm)
5) Chromatin (700nm)
6) Metaphase Chromosome (1400nm)

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11
Q

Histones that form Histone protein core

A
  • H2A
  • H2B
  • H3
  • H4
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12
Q

Chromatosome

A

Nucleosome bound to a H1 histone protein and adjacent Linker DNA

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13
Q

Non-Histone Proteins

A
  • HMG (high mobility group)
  • SMC (struct. maintenance of chromosome)
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14
Q

Condensin

A

Type of Structural maintenance of Chromosome (SMC) that extrudes and stabilizes DNA
(Activated by CDK)

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15
Q

What phase do we usually find chromatin in?

A

Interphase

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16
Q

Superspirilization in Prokaryotes

A
  • Positive Superspiralization (Overwound DNA)
  • Negative Superspiralization (Underwound DNA)
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17
Q

Linking Number

A

Number that describes linking of 2 closed circular DNA
Twists + Writhes

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18
Q

Twists

A

Right-handed helical turn

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19
Q

Writhes

A

Suprahelical turn in Negative Left-handed orientation
(unwinding a twist leads to writhes)

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20
Q

Topoisomerases

A

Enzymes that relieve Torsional stress during DNA replication
Tyrosine active site

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21
Q

Type I Topoisomerase

A
  • Acts on 1 strand only
  • No energy
  • Changes linking n. by 1
  • Creates nick
    (only for negative supercoiling in Prokaryotes)
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22
Q

Type II Topoisomerase

A
  • Acts on both strands
  • Requires ATP
  • Changes linking n. by 2
  • e.g DNA Gyrase
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23
Q

Human Genome

A

All genetic information in a cell which includes Nuclear and Mitochondrial DNA
(apx. 3 Billion BP)

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24
Q

Length of the Human Genome

A

2m

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25
Q

Mitochondrial Genome

A

Circular DNA with No Histones, No Introns!
37 total genes, 13 protein coding.
22 tRNA
2 rRNA
(mRNA is Polycistronic)

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26
Q

Polycistronic

A

One coding region can code for more than one peptide
(only in prokaryotes/mitochondria)

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27
Q

What does Mitochondrial DNA lack?

A

5’ Cap

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28
Q

5’ Cap

A

Modified Guanosine neuc. added to 5’ end of mRNA in Eukaryotes

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29
Q

What determines the complexity of the Human Genome?

A

The number of non-coding regions (introns)

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30
Q

Gene

A

Entire nucleic acid sequence that is necessary for the synth. of a functional gene product

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31
Q

What are Eukaryotic genes made up of?

A
  • Promoter region
  • Open Reading Frame (ORF)
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32
Q

Promoter region function

A
  • Initiates Transcription
  • Binds RNA Polymerase
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33
Q

2 Parts of the Promoter region

A

1) Core promoter
3) Proximal promoter

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34
Q

Core promoter

A
  • Region initiating transcription
  • Initiator element (Inr) with Start codon
  • DPE & MTE for preinitiation complex
  • TATA Box
  • B-recognition element (BRE)
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35
Q

Downstream Promoter Element (DPE) function

A

Binds Factor II D which helps recruit RNA Polymerase

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36
Q

TATA Box

A
  • Rich in Thymine and Adenine
  • Defines direction of Transcription
  • Recognized by TBP, TFIID
  • (-25)
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37
Q

B-recognition element (BRE)

A
  • Upstream of TATA box
  • Binds Factor II B, to start transcription (starting point)
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38
Q

Initiator element (Inr)

A
  • Recognized by TFIID
  • Near transcription site
  • Can sub. TATA
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39
Q

Proximal Promoter

A
  • Upstream of Core Promoter
  • CAAT Box
  • GC Box
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40
Q

CAAT Box & GC Box

A
  • Binds regulatory proteins or transcription factors (enhancers)
  • (-80) CAAT
  • (-100) GC
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41
Q

Open Reading Frame (ORF)

A

Region of the gene that is transcribed to an RNA molecule from START to STOP codons

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42
Q

How do Enhancers/Silencers interact with Promoter region?

A

Formation of a DNA loop by folding so that e/s is in close prox. to the promoter region

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43
Q

Mechanisms of Enhancer Regulation

A

1) Rigid Model (Enhanceosome)
2) Flexible Model (Billboard)
3) Collective Model

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44
Q

3 Types of Exons

A

1) Initiator Exon (splice site + start)
2) Internal Exon (2x splice site)
3) Terminal Exon (splice site + stop)

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45
Q

Alternative Splicing

A

Process that allows single gene to code for multiple proteins
So exon can be intron of other protein (vice versa)

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46
Q

Insulators

A

Regulatory gene sequences binding insulator proteins

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47
Q

Types of Insulators

A
  • Barrier Insulators
  • Enhancer Insulators
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48
Q

Barrier Insulators

A

Sequence before a gene preventing heterochromatization, allowing transcription

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49
Q

Enhancer Insulators

A

Sequences between enhancers and promoters to stop DNA loop formation
(No interaction of promoter & e/s)

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50
Q

Psudogenes

A

DNA sequences resembling a functional gene but have MUTATIONS that prevent proper expression
(Gene-Like structures)

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51
Q

Pseudogene functions

A
  • Can code for Pgk2
  • Used as template for transcription (non-coding)
  • 3D chromatin interaction (stabilize DNA)
  • Gene conversion (rare)
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52
Q

Direct Pseudogene formation

A
  • Gene mutation (Point)
  • Non-processed pseudogene
  • e.g L-gulonolactone oxidase showing humans were once able to produce VitC (gene fossil)
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53
Q

Indirect Pseudogene formation

A

Reverse transcription of mRNA/RNA back to DNA inserting into chromosomal DNA (processed pseudogene)

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54
Q

Transposons

A

Segments of DNA that can move around to different positions in the genome of a single cell
(jumping genes)

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55
Q

Class II Transposon

A
  • DNA Transposon
  • Sequence cut and pasted to new place
  • Transposase enzyme used
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56
Q

Class I Transposon

A
  • Retrotransposon
  • Copy and paste but RNA (RNA poly)
  • RNA then back to DNA (reverse transcriptase) then integrated (Integrase)
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57
Q

Types of Interspersed Repeats

A
  • LINEs
  • SINEs
  • LTR Elements
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58
Q

LINEs

A

Long Interspersed Nuclear Element
- Retrotransposon
- Codes for ORF1 (p40 mRNA) & ORF2 (endonucleases & rev. transc.)

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59
Q

SINEs

A

Short Interspersed Nuclear Element
- Parasite transposed element using LINE elements to multiply (ORF1/2 & reverse transcriptase and endonuclease)

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60
Q

LTR Elements

A

Long Terminal Repeat Elements
- Retrotransposons
- Found at end of retrovirus genome
- For integration of Virus into host DNA

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61
Q

What virus is integrated in Human genome

A

HERV
Human Endogen Retrovirus
8% integration

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62
Q

Tandem Repeats

A

Repeat sequences one after the other with no breaks or bases in bw
Formed by DNA slippage

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63
Q

Types of Tandem Repeats

A
  • Microsatellite (1-9 bp)
  • Minisatellite (10-100 bp)
  • Macrosatellite (100+ bp)
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64
Q

What causes Fragile X Syndrome

A

Mutations in FMR1 Gene
(CGG repeat)

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65
Q

Type I DNA Dependent DNA Polymerase

A
  • Synthesis, 3’ & 5’ Exonuclease activity
  • Particularly works on Lagging strand
  • Role in repair
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66
Q

Type II DNA Dependent DNA Polymerase

A
  • DNA Repair
  • Synth & 3’ Exonuclease
  • Not required for DNA replication
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67
Q

Type III DNA Dependent DNA Polymerase

A
  • Replication
  • α, ε, and θ Subunits for synth.
  • 2 B subunits for attachment
  • Synth & 3’ Exonuclease
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68
Q

OriC

A

Single defined replication origin in Prokaryotes

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69
Q

DNA separation in Prokaryotes

A
  • dnaA recognize OriC and bind dnaA box
  • dnaB & dnaC form Helicase-like complex
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70
Q

Primosome

A

Group of proteins that help initiate DNA replication by setting up proper conditions needed for synthesis

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71
Q

Parts of the Primosome

A
  • HD-proteins: Keep DNA single stranded
  • N-proteins: attached to dnaB & dnaC
  • Primase / dnaG: Synth. RNA primer
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72
Q

Replisome

A

Combination of Primosome and DNA polymerase III

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73
Q

What does DNA ligase use for energy in Prokaryotes?

A

NAD +

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74
Q

What happens in G1?

A

1) ORC to starting point on DNA
2) CdC6 & Cdtl proteins form complex similar to dnaB/C (helicase)
3) Mcm form pre-initiation complex, active helicase

75
Q

What inhibits mcm proteins?

A

CdC6 and Cdt1 because they are the ones who recruit it

76
Q

Cyclins

A

Family of regulatory proteins
- Can switch on specific CDKs
- CDKs phosphorylate proteins

77
Q

What happens in S phase?

A

1) Cdc6 phosphorylated by CDKs
2) Mcm not inhibited anymore by cdc6
3) Helicase activity
4) ORC phosphorylated and inhibited to prevent re-initiation

78
Q

α - DNA Polymerase

A

Only synthesizes initial DNA segment
- Extends RNA primer by 25-ish nucleotides (mixed RNA-DNA primer)
- Forms a tetramer complex with Primase

79
Q

β - DNA Polymerase

A

DNA Repair
(similar to DNA polymerase I in prokaryotes)

80
Q

γ - DNA Polymerase

A

DNA synthesis in the Mitochondria

81
Q

δ - DNA Polymerase

A

DNA synthesis on Lagging strand

82
Q

ε - DNA Polymerase

A

DNA synthesis on Leading strand

83
Q

PCNA

A
  • Sliding clamp
  • Ensures that δ and ε DNA polymerases dont dissociate from template
  • Increases processivity of the polymerase
84
Q

RFC

A

Clamp Loader
Inserts and opens PCNA ring to encircle region of DNA synthesized by polymerase alpha

85
Q

What removes Ribonucleotides at 5’ end of Okazaki fragments

A
  • Ribonuclease H
  • FEN I
    (5’ exonuclease activity)
86
Q

Telomerase

A

Enzyme that adds telomeric repeat sequences to 3’ ends of each chromosome to compensate for shortening due to RNA primer removal on lagging strand

87
Q

Hayflick limit

A

Limit of cell division before the telomere is too short
(Ageing)

88
Q

What stabilizes the T-loop

A

Shelterin complexes

89
Q

Shelterin complexes

A
  • TRF 1 / 2 (inh. telomerase)
  • TIN 2
  • TIPP 1 (activates telomerase)
  • POT 1
90
Q

POT 1 and TRF 2 significance

A

Sheltrin proteins that inhibit ATM and ATR which are kinases that recognize telomere as damage

91
Q

p53

A

Tumor supressor protein
- Checks DNA during G1 before replication
- All corrected before S phase

92
Q

Common types of DNA damage

A
  • Thymine dimers
  • Modification of bases by exo and endo agents
  • Loss of Purine base
  • Deamination
93
Q

DNA intercalators

A

Modify structure of the double helix causing breakage and stoppage of replication

94
Q

What types of DNA damage happen spontaneously?

A
  • Loss of a Purine base
  • Deamination
95
Q

Direct Repair

A

Damage is identified and corrected
(present in prokaryotes to repair Thymine dimers using photolyase)

96
Q

Base Excision repair

A

Damaged base is removed and missing part of the chain is resythesized
(Deamination and loss of purine base repaired)

97
Q

Nucleotide Excision repair

A

Entire DNA segment with the false conformation is removed , then resynthesized
(Repair of thymine dimers)

98
Q

Mutation

A

Permanent alteration in DNA (<1%)

99
Q

Types of chromosome mutations

A
  • Deletion, Insertion, Repeats
  • Inversion
  • Translocation
100
Q

Polymorphism

A

Genetic variation that is present in opulation with high allele freq. (>1%)

101
Q

DNA Deamination

A

Loss of an amino group from Bases of DNA, generating a foreign base.
- Oxidative deamination
- Keto group replaces amino
- Cytosine most common

102
Q

Deamination of Adenine

A

Hypoxanthine
(pairs to C)

103
Q

Deamination of Guanine

A

Xanthine
(pairs to C)

104
Q

Deamination of Cytosine

A

Uracil
(pairs to A)

105
Q

Repair of DNA Deamination

A

Base Excision Repair
1) Glycosidase enzyme removes deaminated base (AP site)
2) AP endonuclease removes sugar
3) DNA polymerase I/B resynth
4) DNA ligase adds ester bond

106
Q

Thymine dimers

A

2 Thymines break their double bonds with Adenine and form 2 single bonds with each other
(also C-C or C-T)

107
Q

What causes Thymine dimers

A

UV light
by electron excitation

108
Q

Why is Thymine dimer bad

A

2 Thymines will be read as 1, so only 1 adenine is added to the strand
(replication and transcription inhibited)

109
Q

Repair of Thymine Dimers

A

Nucleotide Excision Pair
1) Specific endonuclease used to remove whole segment
2) DNA polymerase I/B resynth
3) DNA ligase adds ester bond

110
Q

Difference between base and nucleotide excision pair

A

Glycosidase is used first in a base excision
in Nucleotide excision, we use a special endonuclease only

111
Q

Repair of Thymine Dimers in Prokaryotes

A

Direct repair
Photolyase enzyme which can reverse dimerization
Using UV light

112
Q

DNA mismatch

A

DNA damage caused by incorrect pairing of 2 bases on double helix

113
Q

Repair of DNA mismatch, how do we know which base is incorrect?

A

During synthesis, the template strand is methylated and the synthesized isnt methylated for a while

114
Q

Repair of DNA mismatch

A

1) MutS2 recognizes the mismatch
2) MutH endonuclease attaches to wrong base (inactive)
3) MutL2 activates MutH to cut region of unmethylated DNA, & UvrD helicase
4) Exonuclease breaks strand from hemi-methylated region to mismatch
5) DNA polymerase III and Ligase

115
Q

Repair of DNA mismatch, why dont we use DNA polymerase I?

A

Because its too slow
DNA Polymerase III is needed to synthesize a long segment

116
Q

Point Mutation

A

Base change with a low allele frequency (rare)

117
Q

Single Nucleotide Polymorphism (SNP)

A

Base change with High allele frequency (common)

118
Q

Same sense, Synonymous, Silent mutation

A

Nothing happens to the amino acid sequence

119
Q

Missense Mutation

A

Change of one of amino acids

120
Q

False splicing

A
  • If one Intron remains after splicing, mRNA is longer than it should be.
  • If one Exon is missing then part of the protein is missing
121
Q

Nonsense mutation

A

Amino acid codon is replaced by a stop codon
Truncated protein (shorter than it should be)

122
Q

Frameshift

A

When a base is inserted or deleted from the coding sequence causing shift.
(can also cause a nonsense mutation)

123
Q

Diseases caused by Trinucleotide repeats

A
  • Fragile X Syndrome
  • Myotonic Dystrophy
  • Huntington disease
124
Q

Diseases caused by Point Mutations

A
  • Sickle Cell Anemia
  • PKU
125
Q

Diseases caused by SNP

A
  • Cystic Fibrosis
126
Q

Huntington Disease

A

CAG repeat (poly-glutamine in protein)
Proteases cant degrade proteases
(neurodegenerative)
Autosomal Dominant

127
Q

Sickle Cell Anaemia

A

Point Mutation of Hb B-gene
Glu to Val change
Altered surface molecules
Recessive allele

128
Q

Phenylketonuria

A

Mutation of Phenylalanine Hydroxylase
Cofactor Deficiency (BH4)

129
Q

Cystic Fibrosis

A

CFTR protein mutation
Nonsense Mutation
Autosomal Recessive
(Genetherapy, adenovirus containing CFTR gene)

130
Q

Methods of Identifying Genetic Factors

A
  • Genome wide association study (GWAS)
  • Candidate Gene Analysis
  • Case-control Study
  • Transmission disequilibrium test
131
Q

Genome Wide association study (GWAS)

A
  • Polymorphisms are in the whole genome
  • No hypothesis needed
  • Stats. analysis for correction of multiple tests
132
Q

Candidate Gene Analysis

A
  • Hypothesis set before analysis
  • Selected genes analyzed
  • Sometimes important targets can be left out
133
Q

Case Control Study

A

Allele or Genotype frequencies of Case and Control groups compared to check for difference.
(GWAS & Candidate used)

134
Q

Transmission disequilibrium test

A
  • Affected child is studied to see what allele came from what parent
  • Only heterozygote parents included in the study
  • If there is a monogenic disorder they will be effected
  • Compares rates of alleles transmitted and untransmitted to the affected offspring from the parents
135
Q

What does PCR stand for

A

Polymerase Chain Reaction

136
Q

PCR is…

A

Artificial method of replicating DNA in lab
It is a form of in vitro DNA rep.

137
Q

PCR vs Normal replication

A

PCR only a small part of the genome is replicated, while in normal the whole genome is replicated

138
Q

How do we separate strands in PCR?

A

High temperature only, no proteins needed
(denaturation step)

139
Q

How many cycles of replication in PCR?

A

35 - 40 semi-conservative replication cycles in a Thermocycler

140
Q

3 steps of PCR

A

1) Denaturation
2) Annealing
3) Elongation

141
Q

PCR Denaturation

A

90 - 95 degrees
Separation of Strands
Only hydrogen bonds break

142
Q

PCR Annealing

A

Cooled to 50 - 72 degrees
25 - 30 seconds
Allows Primers to Anneal/Bind

143
Q

Primers in PCR

A

Are DNA!!!
ssDNA (16-30) synth. in test tubes

144
Q

How do we determine the Annealing Temp?

A

Based on the melting temperature of the ssDNA primer
Too High: no H-bond formation
Too Low: non-spec. binding of primer

145
Q

PCR Elongation

A

Heated to 68 - 72 degrees
Optimal temperature for DNA polymerase
Taq DNA polymerase used as it is thermostable
Keeps elongating till Denaturation temp is reached

146
Q

When do we get the correct sized product in PCR?

A

When the synthesized strand from the 1st cycle is used as a template.
Using original DNA causes overhanging of strand.

147
Q

Components of PCR reaction mixture

A
  • DNA template
  • ssDNA oligonucleotide primer
  • dNTPs
  • Taq DNA polymerase (therm.stab)
  • Buffer (for optimal env.)
148
Q

What do we use to see PCR results?

A

Agarose Gel Electrophoresis and DNA ladder to compare.
+ Intercalator dye (Ethidium Bromide)

149
Q

Novel Polymorphism

A

Genetic variation in DNA that has not been previously characterized or documented

150
Q

Sanger Sequencing

A

Direct detection of nucleotide sequence
1) Primer added to DNA strand of interest
2) DNA poly. extends the primer
3) Both dNTP and specific ddNTP incorporated to see where it binds
4) When ddNTP, no 3’ OH group so no ester bonds formed so it stops
5) Different length DNA fragments to be separated by size

151
Q

Next Generation Sequencing (NGS)

A

One DNA sample is sequenced several times.
We can measure qualitatively by checking pH or PPi after each nucleotide added
PCR based method

152
Q

Primer Extension Method - Mini Sequencing

A

‘Mini’ because we need 1 single primer
Only elongate primer by 1 nucleotide.
Color labelled ddNTPs, added complementary next to primer

153
Q

Restriction Fragment Length Polymorphism (RFLP)

A

Changes a sequence difference to a length difference
C/T Polymorphism
Type II restriction endonuclease needed (highly specific)
T - perfecT recognition
Cut, length analyzed

154
Q

Allele Specific PCR

A

Special DNA polymerase needed with no 3’ exonuclease activity
- Primer ends ON the SNP not before
- if complementary it continues
- if not it stops
- 3’ exo. would just cut the wrong base and keep going which defeats the whole purpose

155
Q

Prokaryotic Transcription Strands

A
  • Template strand
  • Coding strand
156
Q

Can transcription start without a primer in Prokaryotes?

A

Yes, because RNA polymerase is used

157
Q

Proofreading in RNA polymerase?

A

No, no 3’ exonuclease activity as RNA copy leaves the nucleus so no need, wont be genetically inherited

158
Q

What is prokaryotic transcription unit split into?

A
  • Promoter region (-10, -35)
  • Transcribed region
159
Q

2 forms of RNA polymerase

A
  • Holoenzyme
  • Apoenzyme
160
Q

Holoenzyme RNA Polymerase

A

Core + σ subunit (5)
(2a, B, B’, σ)
Can initiate transcription
Low affinity (1s) searching

161
Q

Apoenzyme RNA polymerase

A

4 subunits (2a, B, B’)
Can only elongate the RNA chain
High affinity (60min) holding

162
Q

Role of σ Subunit in RNA polymerase

A

Initiates transcription by interaction with promoter region

163
Q

Is helicase used in Prokaryotic transcription

A

No
RNA Polymerase can unwind helix

164
Q

Inhibitor of RNA polymerase in Prokaryotes

A

Natural Rifamycin
Binds to B subunit and prevents initiation

165
Q

Termination of Transcription types in Prokaryotes (2)

A
  • Rho independent termination
  • Rho dependent termination
166
Q

Rho independent Termination

A

1) RNA pol. reaches termination sequence
2) Termination sequence forms hairpin loop (G-C), poly. slows
3) Loop followed by U rich sequence
4) RNA strand pulled out of pol. due to weak U H-bonds.

167
Q

Rho dependent Termination

A

1) Rho (ρ) factor Helicase follows RNA polymerase
2) Uses ATP
3) RNA poly. slows down, Rho (ρ) factor catches up
4) Rho (ρ) factor pulls RNA strand out, because no U rich sequence after

168
Q

Post-transcriptional RNA modifications in prokaryotic cells

A

RNA transcript has tRNA and rRNA coding segments which can be modified after being cut out by endonuclease (RNase)
e.g addition of CCA sequence to tRNA on 3’ end

169
Q

Operon

A

One transcription unit that can code for more than one protein
Only in Prokaryotes

170
Q

Ribosome binding sites (RBSs)

A

Located upstream of Start codon
1st cistron RBS in 5’UTR, none in 3’

171
Q

Activator / Repressor Regulatory Proteins

A

Bind to regions in the Promoter called Operator regions

172
Q

Name of immature mRNA

A

premRNA or hnmRNA

173
Q

Type II RNA Polymerase

A

premRNA to mRNAs
Can not initiate transcription

174
Q

a-amanitin

A

Death cap mushroom poison that inhibits transcription by inhibiting RNA polymerase

175
Q

Initiation of Transcription in Eukaryotes

A

1) TFIID binds TATA
2) TFIIA/B –> core prom. –> TFIIF brings RNA Polymerase II
3) TFIIH unwinds double helix at INR using ATP

176
Q

Termiantion of Transcription in Eukaryotes

A

1) CPSF and CstF follow RNA polymerase II
2) CPSF detects stop codon (Poly-adenylation)
3) CPSF binds with high affinity to sequence and detaches from polymerase with help of CstF.

177
Q

Exon def

A

Part of the gene that remains in the mRNA after maturation

178
Q

5’ cap formation

A

1) 1st nucleotide is usually ATP, RNA terminal phosphatase removes 1 phosphate
2) GTP added to ATP by Guanylyl transferase enzyme, PPi released
3) Methylated by methyltransferase enzyme (SAM donor)

179
Q

5’ cap function

A
  • Maturation signal
  • Protective measure (shields from 5’ exonuc.)
  • Initiation of Translation (elF4E)
180
Q

Splicing

A

Splice sites bw introns and exons.
Inside Splicosome:
1) branching adenine attacks 5’ splice site forming loop (lariat)
2) Then attacks 3’ splice site linking exons together

181
Q

snRNPs in Splicing

A
  • U1: 5’ splice site
  • U2: Branching site (adenine)
  • U5: 3’ splice site
    ALL FORM SPLICOSOME
182
Q

Poly-A Tail formation

A

During termination of transcription
1) CSPF inactive following RNA polymerase II
2) Stop codon reached (TTATTT), AAUAAA transcribed on mRNA
3) CSPF recognizes and recruits CstF to cleave transcript
4) Polyadenylate polymerase enzyme add 150-200 adenine nucleotides
(Polyadenylate BP cover tail)

183
Q

Transport of the ready mRNA outside of the nucleus

A

1) mRNA covered by proteins recognized by Nuclear export receptor that its mature
2) Works with Ran GTP BP to direct mRNA to nuclear pore
3) 5’ Cap binding complex switched to Cytosolic cap binding proteins after exiting
4) Loop forms, Poly-A tail touches 5’ Cap

MCB 1 (3 decks)

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