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Genetics Test #1 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

Transcription

A

Synthesis of an RNA molecule using a DNA template

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2
Q

RNA Polymerase

A

Used in transcription

Transcribes one strand of DNA

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3
Q

DNA is read

A

3’ to 5’

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4
Q

RNA is synthesized

A

5’ to 3’

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5
Q

Template strand

A

Non-coding strand used by RNA Polymerase

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6
Q

Coding Strand

A

Non-template Strand not used by RNA Polymerase

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7
Q

Uracil vs Thymine function

A

Uracil: more flexible, can wobble pair
Thymine: more resistant to damage

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8
Q

5 types of RNA

A 
mRNA
tRNA
rRNA
snRNA
siRNA and miRNA
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9
Q

mRNA

A

Encodes amino acid sequence of polypeptide

Contain translated and untranslated regions

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10
Q

tRNA

A

Brings amino acid to ribosome during translation

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11
Q

rRNA

A

Forms ribosome with proteins

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12
Q

snRNA

A

Small nuclear
Combines with proteins to form complexes like spliceosomes used in various processes like intron splicing
Only in eukaryotes

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13
Q

siRNA and miRNA

A

Short interfering and micro

Involved in gene silencing in some eukaryotes

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14
Q

Coding RNAs

A

Translated into proteins

Only mRNA

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15
Q

Noncoding RNAs

A

All RNAs except mRNA

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16
Q

3 steps of Transcription in pro and eukaryotes

A

Initiation
Elongation
Termination

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17
Q

Initiation in Prokaryotes

A

Sigma factor of RNA Polymerase recognizes -35 and -10 regions

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18
Q

Elongation in Prokarotes

A

Sigma factor released and core RNA polymerase continues

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19
Q

Termination in Prokaryotes

A

By rho-dependent or independent terminators

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20
Q

3 regions of prokaryotic gene

A

Promoter sequence
RNA-coding sequence
Terminator

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21
Q

Promoter sequence function

A

Attracts RNA Pol to being txn at site specified by promoter

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22
Q

RNA-coding sequence in Prokayotes

A

Transcribed sequence

Begins at +1 and includes translated and untranslated regions in an mRNA

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23
Q

Terminator

A

Specifies where txn stops

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24
Q

Gene=

A

Sequence from Promoter to Terminator

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25
Promoter sequences in prokaryotes
-35 and -10 regions, upstream of +1 | Both recognized by sigma factor of RNA Pol which binds to regions and positions core enzyme
26
Transcription initiation requires
RNA Pol holoenzyme to bind to promoter
27
Holoenzyme
Complete enzyme Consists of Core enzyme (4 subunits-2 alpha and 2 beta) and sigma factor
28
Sigma factor
Can change depending on conditions Released after 8-9 nucleotide pairs have been joined in growing RNA chain Then used for other initiations
29
2 types of terminator sequences in prokaryotes
Rho-independent and Rho-dependent
30
Rho-independent
Type 1 Twofold symmetry (internal base pairing) that allows hairpin loop to form and this stalls RNA Pol Have a Poly-U region (4-8 U) after hairpin loop Make an unstable structure and cause termination (AU)
31
Rho-dependent
Type 2 No hairpin or poly-U Contain rut (rho-utilization sequence) Rho factor binds to rut, moves along RNA until it hits DNA-RNA region, and uses its helicase to separate RNA from DNA
32
How many polymerases in Pro and Eukaryotes?
Pro: One Eu: Three (focus on RNA Pol II)
33
Product of RNA Pol II
pre-mRNA
34
Eukaryote Promoters
Core and proximal promoter elements
35
Core promoter elements
Located near +1 and specify where transcription begins Required for initiation Includes initiator element (Inr) and TATA box Alone allows a low level of txn
36
Initiator element
Part of core promoter | Spans +1
37
TATA box
Part of core promoter | About -30
38
Proximal promoter elements
-50 to -200 DNA sequence that binds to activators Required for high levels of initiation Ex: CAAT box and GC box
39
CAAT box
Proximal promoter element at about -75
40
GC box
Proximal promoter element at about -90
41
Transcription initiation in Eukaryotes
TFIID binds to TATA box TFIID attracts other TFs and RNA Pol II to core promoter TFIIH (helicase) starts to unwind DNA and elongation ready to begin
42
Activators
Proteins that bind to proximal elements and enhancers Determine when and how much a gene is expressed Enhance transcription by recruiting RNA Pol to promoter
43
Enhancers
Sequences required for maximal txn of some genes Behave like proximal elements (also bind activators) but can be up or downstream of +1 May function from a distance of 1000s of bps away from +1 by DNA looping
44
Cis-acting elements
Control only genes on the same DNA molecule | Ex: Promoters and enhancers
45
Trans-acting elements
Control genes on different DNA molecules | Ex: genes that encode activators
46
Housekeeping genes
Used in all cell types for basic functions Ex: actin Have common proximal elements and are recognized by activators found in all cell types
47
Non-housekeeping genes
Expressed only in some cell types or at particular times | Have specialized proximal elements/enhancers recognized by activators found only in specific cell types or times
48
3 types of processing for mRNA
5' capping 3' polyadenylation Intron splicing ONLY IN EUKARYOTES
49
5' capping
Capping enzyme adds 7-methyl guanosine (m7g) to 5' end using 5' to 5' linkage 2 adjacent sugars are methylated at 2' oxygen
50
2 jobs of 5' cap
Ribosome binding to mRNA during translation initiation | Protection from 5' to 3' exonucleases because of unusual 5' to 5' linkage
51
3' Polyadenylation
Added after polyA signal of elongation (AAUAAA) is recognized by cleavage factors They cut off RNA 10-30 bases downstream of signal After cleavage, poly(A) polymerase (PAP) adds 50-250 As to 3' end
52
2 functions of PolyA tail
Required for efficient export of mRNA from nucleus to cytoplasm Acts as a buffer against 3' to 5' exonucleases
53
Intron
Non- amino acid coding sequences that intervene the amino acid-coding ones Typically begin with 5' GU and ends with AG 3'
54
Branch-point sequence
AKA Lariat signal About 30 bases upstream of 3' intron splice site Recognized by spliceosome complex made up of small nuclear ribonucleoproteins (snRNPs)
55
snRNPs
snRNAs+ proteins | Make up sliceosome complex
56
Spliceosome
Removes introns from pre-mRNA
57
Exons include
Amino acid-coding sequences and 5' to 3' UTRs
58
Alternative splicing
In most human multiexon genes May occur in different cell types Can generate a set of related proteins that function optimally in each cell type
59
Is pro or eukaryote txn coupled with tln?
Prokaryote
60
Pro vs Eukaryotes genes per mRNA
Pro: often polycistronic Eu: noncistronic
61
Polycistronic vs noncistronic
Poly: contains coding info from more than one question Non: contains coding info from only one gene

Genetics Test #1 (5 decks)

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