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Genetics exam 4 Flashcards

1
Q

Components of DNA

A
  • double stranded
  • deoxyribose as the sugar
  • contains 2’ H
  • uses thymine, cytosine, adenine, guanine
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2
Q

components of RNA

A
  • usually single stranded
  • uses ribose as sugar
  • contains 2’ OH
  • uses uracil, cytosine, adenine, guanine
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3
Q

which is more stable DNA or RNA? Why?

A

DNA is more stable due to its lack of a free hydroxyl group making RNA more rapidly. degradable

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4
Q

secondary structures of RNA?

A

called hairpins, the RNA folds in loops complementary bases on the strand must pair up

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4
Q

primary structure of RNA?

A

single stranded sequence

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5
Q

messenger RNA - mRNA

A

carries coding sequences for proteins from DNA to a ribosome

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6
Q

ribosomal RNA - rRNA

A

components of ribosome (ribosomes synthesize proteins in cells)

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7
Q

transfer RNA - tRNA

A

incorporates amino acids during translation

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8
Q

small nuclear RNA - snRNA

A

combine with small protein subunits to form snRNPs, where some convert pre-mRNA into mRNA

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9
Q

microRNA - miRNA

A

regulation of translation

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10
Q

small interfering RNA - siRNA

A

triggers degradation of target mRNAs

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11
Q

which classes of RNAs are in prokaryotes and eukaryotes?

A

prokaryotes and eukaryotes
- mRNA
- rRNA
- tRNA
eukaryotes only
- snRNA
- miRNA
- siRNA

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12
Q

pre-messenger RNA - pre-mRNA

A

intermediate products of transcription in eukaryotic cells only and are modified before becoming mRNA and exiting the nucleus for translation into protein

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13
Q

what is transcription?

A

synthesis of cellular RNAs from DNA. Only parts of the DNA molecule are copied

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14
Q

what is required for transcription?

A
  • a DNA template
  • raw materials needed to build RNA molecule - ribonucleotide triphosphate
  • proteins to catalyze synthesis of RNA
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15
Q

template strand

A

transcribed strand of DNA

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16
Q

what is the direction that RNA is synthesized?

A

5’ to 3’ direction and synthesis is complimentary and antiparallel to the template

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17
Q

does RNA require a primer to initiate synthesis?

A

no

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18
Q

promoter region

A

DNA sequence that the transcription apparatus recognizes and binds. the promoter indicates which DNA strand is to be read as the template.

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19
Q

transcription unit

A

promoter, RNA coding region, and a terminator

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20
Q

terminator

A

sequence of nucleotides that tells transcription where to end

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21
Q

Bacterial transcription - RNA polymerase

A

has several polypeptide chains - 5 subunits that make up the core enzyme - two copies of alpha, a beta, beta’, and omega

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22
Q

sigma factor

A

controls binding of RNA polymerase to the promoter so that transcription is initiated at the correct location

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23
Q

what does the core enzyme do?

A

catalyzes the elongation of RNA molecule by addition of RNA nucleotides

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24
consensus sequence
set of most commonly encountered nucleotides among sequences that possess a lot of similarity
25
-10 consensus sequence
most common consensus sequence in bacterial promoters usually written as TATAAT
26
-35 consensus sequence
lies 35 bp upstream of start site - other common sequence in bacterial promoters
27
holoenzyme
5 subunits of core enzyme plus sigma binds and unwinds the double stranded DNA
28
four steps of initiation
1. promoter recognition 2. formation of transcription bubble 3. creation of first rNTP bonds 4. escape of apparatus from promoter and then elongation
29
when does elongation begin?
after around 9-12 nucleotides are successfully added
30
what happens when the transcription bubble moves beyond the promoter region?
the sigma factor falls off and the RNA polymerase changes shape as it can no longer bind the promoter
31
rho dependent terminator
cause termination of transcription only in presence of ancillary protein called rho factor
32
rho independent terminator
do not need rho factor to bring about end of transcription contain inverted repeats and string of 6 adenines following 2nd repeat which produce string of uracils after the hairpin making the polymerase pause
33
rut site
DNA sequence upstream of the terminator that encodes RNA rich with cytosine and no secondary structures that serves as a binding site for the rho factor
34
polycistronic
one mRNA encodes for multiple proteins
35
how many RNA polymerases do eukaryotes have?
three
36
RNA polymerase I
large rRNAs
37
RNA polymerase II
pre-mRNAs, some snRNAs, and miRNAs
38
RNA polymerase III
tRNAs, small rRNAs, some snRNAs and miRNAs
39
what is basal transcription regulated by?
core promoter which is bound by general transcription factorsw
40
what is enhanced transcription regulated by?
regulatory promoter which is immediately upstream and is bound by transcriptional activator proteins
41
transcription factors
bind to DNA sequences and affect levels of transcription
42
general transcription fators
combine with RNA polymerase to form basal transcription apparatus
43
basal transcription apparatus
group of proteins that assembles near the transcription start site and initiates minimal levels of transcription
44
where is the core promoter and regulatory promoter located?
core promoter immediately upstream of gene and regulatory is immediately upstream of the core promoter
45
TATA box
consensus sequence TATAAA located -25 to -30 bp upstream of the start site within the core promoter
46
TBP or TATA binding protein
a polypeptide apart of TFIID that recognizes and binds to the TATA box
47
TFIID
first step in initiation is the binding of TFIID to the TATA box on the core promoter. TFIID consists of 9 polypeptides
48
where does the TBP bind to?
the minor groove of the DNA double helix and straddles the DNA like a saddle bending the DNA and partially unwinding it
49
when does elongation start in eukaryotes?
after around 30 bp are synthesized RNA polymerase moves downstream of promoter
50
RNA polymerase in termination
Polymerase III uses mechanism similar to rho-independent termination and polymerase I uses termination factor like rho
51
mutation
inherited change in genetic information
52
where do mutations occur?
within or near genes
53
somatic mutation
occur in non reproductive cells - through mitosis is where they are inherited and population new generations of cells
54
germ line mutation
occur in reproductive cells and are inherited through sexual reproduction
55
codon
3 nucleotides that code for a specific amino acid
56
reading frame
series of codons that code for amino acids in polypeptide chain
57
how is the reading frame established?
by the start codon always AUG encoding for MET
58
base substitution
one whole codon is changed as a result of one nucleotide changing
59
transition
purine/purine or pyrimidine/pyrimidine
60
transversion
purine/pyrimidine or pyrimidine/purine
61
purine
A/G
62
pyrimidine
T(U)/C
63
base insertion
when one or more nucleotides are added to a segment of DNA
64
base deletion
when one or more nucleotides is removed from a segment of DNA
65
what does a single nucleotide insertion or deletion cause?
reading frame shift
66
what does an in frame insertion of a whole segment cause?
inserts an extra amino acid and the reading frame is maintained
67
missense mutation
base substitution that results in different amino acid
68
nonsense mutation
nucleotide bp is changed results in a premature stop codon
69
silent mutation
no change in amino acid sequence with some have phenotypic affects
70
forward mutation
alters the wild type phenotype
71
reverse mutation
changes mutant phenotype back to wild type
72
suppressor mutation
hides or suppresses effect of another mutation - produces individual that has original mutation and suppressor mutation but presents as wild type pheontype
73
intergenic suppressor mutation
located in a different gene from original mutation
74
intragenic suppressor mutation
located in the same gene but different site as the original mutation
75
what are the three main causes of mutation?
1) DNA replication errors during replication 2) DNA damage after replication 3) transposons/viral insertions
76
what are trinucleotide repeats associated with?
they cause a hairpin during replication resulting in extra repeats being replicated and often causes disease
77
what do expansions of nucleotide repeats lead to?
lead to the deactivation of nearby genes
78
what is the most common cause of spontaneous replication errors?
tautomeric shifts
79
spontaneous mutations
mutations that occur under normal conditions
80
induced mutations
mutations that result from environmental chemicals or radiation
81
tautomeric shifts
when positions of protons in the DNA base changes resulting in anomalous base pairing
82
anomalous base pairing arrangements
- rare form of cytosine pairs with common form of adenine - common form of thymine pairs with the rare form of guanine
83
wobble base pairing
responsible for some mispairings during replication. thymine and guanine can pair through wobble and adenine and cytosine can pair through wobble when adenine is protonated
84
strand slippage
occurs when one nucleotide strand forms a small loop.
85
what occurs when a strand slippage occurs on the new strand?
results in an insertion, when replicated both strands have the insertion
86
what occurs when a strand slippage occurs on the template strand?
new strand will have a deletion and the deletion will remain with new round of replciation
87
transposons
mobile genetic elements
88
do transposons move autonomously in the genome?
no they move semi autonomously
89
what does transposition require?
enzyme called transposase
90

Biology (8 decks)

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