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Kaplan Biochemistry > Ch. 7: RNA and the Genetic Code > Flashcards

Ch. 7: RNA and the Genetic Code Flashcards

1
Q

central dogma of molecular biology

A

DNA (reverse) transcription RNA —> translation —> protein

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2
Q

how is mRNA made

A

transcribed from the template DNA strand by RNA polymerase then derived from from post transcriptional modifications to hnRNA

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3
Q

what does mRNA do

A

carries info specifying the amino acid sequence of the protein to the ribosome

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4
Q

codon

A

three - nucleotide segment that codes for proteins

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5
Q

how is mRNA monocistronic?

A

each molecule translates into only one protein product

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6
Q

what does tRNA do

A

recognizes and pairs with appropriate codon on an mRNA molecule while in the ribosome

forms high energy bonds needed to create peptide bonds in translation

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7
Q

where is rRNA made

A

in the nucleolus

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8
Q

what does rRNA do

A

catalyzes the formation of peptide bonds

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9
Q

anticodon

A

sequence on tRNA complementary to a codon on mRNA that allows the tRNA and mRNA to pair

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10
Q

how is condon/anticodon pairing oriented

A

antiparallel

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11
Q

what is the eukaryotic start codon

A

AUG (methionine)

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12
Q

what are the three stop codons

A

UAA (you are away)
UGA (you go away)
UAG (you are gone)

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13
Q

how is the genetic code degenerate

A

more than one codon can code for the same amino acid

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14
Q

wobble position

A

the third nucleotide in a codon that usually varies for amino acids with multiple codons

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15
Q

where do silent or degenerate mutations usually occur

A

the wobble position

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16
Q

what is a silent/degenerate mutation

A

a mutation that has no effect on the amino acid that is expressed

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17
Q

what is a point mutation

A

a mutation that effects one nucleotide

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18
Q

what are expressed mutations

A

mutation that effect the expression of an amino acid sequence

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19
Q

what is a missense mutation

A

mutation that substitutes the amino acid that was originally coded for

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20
Q

what is a nonsense mutation

A

mutation that codes for a stop codon where there wasn’t one originally

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21
Q

reading frame

A

three nucleotides of a codon

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22
Q

what is a frameshift mutation

A

some nucleotides are added or deleted, causing a shift in the reading frame

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23
Q

what occurs during transcription (big picture)

A

creation of mRNA from a DNA template

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24
Q

how is the coding strand similar to mRNA

A

identical except for T/U switch

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25
how is the template strand similar to mRNA
complementary and antiparallel
26
what occurs during translation (step by step)
- DNA unwinds via helicase and topoisomerase - RNA polymerase identifies the promoter region, binds to the TATA box with the help of transcription factors, and synthesizes RNA
27
what does RNA polymerase do
locates genes by searching for promoter regions and synthesizes RNA
28
what are promoter regions
specialized areas of DNA
29
TATA box
RNA polymerase binding site at the 'beginning' of the promoter region
30
what do transcription factors do
help RNA polymerase and to the TATA box/promoter region
31
In what direction is mRNA constructed
5' --> 3' as RNA polymerase moves 3' --> 5'
32
what is the primary product of transcription
heterogenous nuclear RNA (hnRNA) modified --> mRNA
33
what structure carries out splicing
the spliceosome
34
what are introns
noncoding sequences that are removed from the hnRNA in the form of a lariat
35
what are exons
coding sequences that are ligated together in the hnRNA
36
what is the 5' cap
7-methylguanylate triphosphate cap added to the 5' end of hnRNA during transcription that protects the mRNA from degradation in the cytoplasm
37
what is the 3' poly A tail
polyadenosyl tails that is added to the 3' end of the mRNA and protects the sequence from rapid degradation like a time-bomb fuse
38
when has hnRNA matured into mRNA
when exons are ligated and the 5' cap and 3' tail are added
39
what is the product of alternative splicing
multiple variants of proteins created from different combinations of exons from the same original gene
40
how does the mRNA transcript exit the nucleus
nuclear pores
41
where does translation occur
in the cytoplasm and in the ribosome
42
what are the three stages of translation
1. initiation 2. elongation 3. termination
43
what occurs during initiation
- small subunits bind to the 5' cap - initiator tRNA ends to the start codon - large subunit binds to the small subunit - assisted by initiation factors
44
what occurs in elongation
ribosome moves in the 5' to 3' direction, binding to sites A--> P --> E and synthesizing the protein
45
what occurs at the A site
holds the new aminoacyl-tRNA which will be added to the growing chain
46
what occurs at the P site
holds the tRNA that carries the growing chain
47
what occurs at the E site
uncharged tRNA pauses before exiting ribosome
48
what occurs during termination
- stop codons move into the A site - release factor binds to codon, causing H2O to be added - H2O causes termination factors to hydrolyzed polypeptide chain and dissociate subunits
49
what to chaperones do
assist in the protein folding process
50
phosphorylation
addition of phosphate group by protein kinases to activate or deactivate proteins
51
carboxyation
addition of carboxylic acid groups to serve as calcium binding sites
52
glycosylation
addition of ogliosaccharaides to determine cellular destination
53
prenylaton
addition of lipid groups
54
operon
cuter of genes transcribed as a single mRNA
55
structural gene
codes for the protein of interest
56
operator site
- upstream of structural gene - nonstranscribable - capable of binding repressor protein
57
promoter site
- upstream of operator site | - provides place for RNA polymerase to bind
58
regulator ene
- furthest upstream | - codes for repressor protein
59
how do repressors act in inducible systems
bind to operator site and act as a roadblock to transcribing the structural gene unbind in the presence of an inducer
60
negative control mechanisms
binding of protein reduces transcriptional activity
61
how is a repressor removed in an inducible system
inducer binds to repressor so that repressor cannot bind to promoter site
62
positive control mechanisms
binding of a molecule increases transcription of a gene
63
how do repressors act in repressible systems
inactive until it binds with a corepressor, then binds to operator site
64
what are transcription factors
transcription-activating proteins that search the DNA looking for specific binding motifs
65
DNA binding domain of a transcription factor
binds to a specific nucleotide sequence in the promoter region
66
Activation domain of the transcription factor
allows for the binding of several transcription factors
67
enhancers
group of response elements that allows for the control of gene's expression by multiple signals variety of signals can increase transcription --> transcription more likely
68
how does acetylation affect chromatin structure
opens chromatin conformation, allows for increased transcription
69
how does DNA methylation affect chromatin structure
silences genes by attaching methyl groups which prevent transcription

Kaplan Biochemistry (9 decks)

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