Topic 2: Genetic Code and Mutation Flashcards
(94 cards)
1
Q
____: adenine and guanine
A
purines
2
Q
____: cytosine, thymine, uracil
A
pyrimidines
3
Q
each strand of DNA is composed of ____ and _____
A
nucleotides and sugar-phosphate backbone
4
Q
where does the phosphodiester bond occur in DNA? between what two ends?
A
the 5’ phosphate group of a nucleotide and the 3’ hydroxyl group of the adjacent nucleotide
5
Q
bases are _______
A
hydrophobic
6
Q
the complementary strand runs _____ to the main strand
A
anti-parallel
7
Q
__________: the theory that each new DNA duplex has one parental strand and one daughter strand
A
semi-conservative replication
8
Q
purine nucleotides are _____-ringed
A
double
9
Q
pyrimidine nucleotides are _____-ringed
A
single
10
Q
how many base pairs twist with each turn of the double-helix?
A
10 base pairs/turn
11
Q
the proportion of each base pairing is ______
A
equal (30% A = 30% T)
12
Q
DNA replication is _____, forming a replication bubble
A
bidirectional
13
Q
prokaryotes have a ______ origin of replication
A
single, because they have a circular genome!
14
Q
eukaryotes have _______ origins of replication
A
multiple, because they have linear DNA
15
Q
in what order do these proteins work in DNA replication?
- DNA polymerase III
-DNA polymerase I
- helicase
- primase
- SSB
- DNA topoisomerase
- DNA ligase
A
- DNA topoisomerase
- Helicase
- SSB
- Primase
- DNA poly III
- DNA poly I
- DNA ligase
16
Q
what does DNA topoisomerase do?
A
relaxes supercoiling
17
Q
what does helicase do?
A
unwinds the double helix
18
Q
what does SSB do?
A
prevents re-annealing of separated strands
19
Q
what does primase do?
A
synthesizes RNA primers
20
Q
what does DNA poly III do?
A
synthesizes DNA
21
Q
what does DNA poly I do?
A
removes and replaces RNA primer with DNA (cuts out nucleotides)
22
Q
what does DNA ligase do?
A
joins DNA segments together
23
Q
what direction is the template strand read in DNA replication?
A
3’ - 5’, new strand elongates in the 5’ -3’ direction!
24
Q
most of the proteins/enzymes required for replication are apart of the complex called ______
A
replisome
25
replication is done in chunks... what are these "chunks" called?
okazaki fragments!
26
DNA polymerase I uses a 5'->3' ______ activity to remove RNA nucleotides
exonuclease
27
DNA polymerase uses a 5'->3' ______ activity to add DNA nucleotides
polymerase
28
true/false: DNA poly I and DNA ligase are active on both the leading and lagging strand
true! they're just more prominent on the lagging strand
29
true/false: telomeres in prokaryotes
false! they're only in eukaryotes
30
germ-line cells contain ____ that adds repetitive DNA sequences to the ends of telomeres
telomerases (enzyme containing RNA)
31
what is the Hayflick limit?
the number of repetition cycles in a cell's life span (~50-70 cycles)
32
each successful replication ______ the telomeres in somatic cells
shortens
33
what is the central dogma of genetics?
the flow of heredity information (DNA -> transcription -> RNA -> translation -> protein)
34
______: DNA is converted to mRNA
transcription
35
in transcription, the new RNA molecule is synthesized via _________
RNA polymerase
36
what are the three stages of transcription?
1. initiation
2. elongation
3. termination
37
what is the complementary DNA strand to the template strand called?
coding strand
38
______ are regions on the DNA template strand that RNA polymerase recognizes and initiates transcription
promoters
39
transcription ends at _____
termination sequences
40
_____ are regions that are transcribed but will be removed before mRNA is translated (because they don't code for specific proteins)
introns
41
_____ are regions that are transcribed and code for proteins, so remain in the translated mRNA
exons
42
_______ has 5 subunits: 2 alpha subunits, 2 beta subunits and 1 omega subunit
RNA polymerase core
43
how does RNA polymerase switch to its active form? (forming the closed promoter complex)
by binding to a sixth subunit (polypeptide) called "sigma subunit"
44
what are the two promoter region codes for bacteria?
1. 5'-TATAAT-3'
2. 5'-TTGACA-3'
45
when DNA unwinds near the transcription site it forms the ______
open promoter complex
46
true/false: transcription isn't as fast as translation
true
47
true/false: instead of remaining unwound, during transcription the DNA immediately returns to a helix after RNA polymerase passes by
true
48
what are the two termination mechanisms in bacterial transcription?
1. intrinsic terminators
2. rho-dependant
49
how many RNA polymerases do eukaryotes have?
three
50
RNA poly I transcribes: _____
RNA poly II transcribes: _____
RNA poly III transcribes: _____
1. rRNA
2. mRNA
3. tRNA
51
what are the promoter region sequences that RNA poly II bind to in eukaryotes?
TATA box (25 bases upstream of start site)
CAAT box (80 bases upstream)
GC-rich box (90 bases upstream)
52
________ help bind the RNA polymerase to the DNA promoter regions
transcription factors
53
__________ are DNA regulatory sequences that increase gene transcription (give promoter a "boost"!)
enhancer sequences
54
____ repress transcription
silencer sequences
55
_____ state also affects/regulates transcription
chromosome
56
what kind of chromatin is actively transcribed? which kind cannot be transcribed?
1. Euchromatin
2. Heterochromatin
57
when does termination occur in eukaryotes?
once RNA polymerase transcribes the poly-A tail, there's no specific "stop" sequences like in bacteria
58
how is pre-mRNA modified before being exported from the nucleus?
addition of a 5' cap
addition of poly-A tail
splicing (removes introns, joins exons together)
59
how long is a poly-A tail?
20-200 base pairs
60
______: takes the message from mRNA and makes proteins
translation
61
where does translation occur? (where are polypeptides assembled)
ribosomes
62
what is the start codon for translation?
5'-AUG-3'
63
which way does translation occur?
5'-3'
64
which two regions of mRNA are not translated?
1. 5'-untranslated region
2. 3'-untranslated region
65
what are the four main classifications of protein structure?
primary, secondary, tertiary, quaternary structure
66
1. peptidyl site (P site)
2. aminoacyl site (A site)
3. exit site (E site)
are all components of the _________ that contribute to _______
1. large and small ribosomal subunits
2. translation
67
what does the P site in the ribosome do?
holds the tRNA containing the growing polypeptide
68
what does the A site in the ribosome do?
binds the new tRNA molecule
69
what does the E site in the ribosome do?
where tRNA's leave the ribosome
70
what are the three stop codons in eukaryotic translation?
UAG, UGA, UAA
71
true/false: translation can happen simultaneously and continuously
true! it's fast and very efficient
72
each bacterial cell contains ~20 000 ribosomes which is about ____ of the cell's mass
1/4
73
true/false: the genetic code is redundant
true, many different codes for the same amino acid (doesn't really matter which one)
74
why is there a 3rd base wobble in tRNA anticodons?
so that it gives flexibility in case of mutation, if only the last position is altered, we can still code for the proper amino acid
75
complementary base-pairing between the mRNA and tRNA is _______ and __________
anti-parallel and complimentary
76
______: mutations are passed from one generation to the next
germ-line mutations
77
____: mutations can alter subsequent generations of cells due to mitosis but AREN'T passed down to further generations
somatic mutation
78
_______: mutation confined to a specific base-pair or gene location
point mutations
79
what are the different "levels" of a point mutation?
amino acid level
RNA level
DNA level
80
what do we call point mutations at the amino acid level?
synonymous, non-synonymous
81
what do we call point mutations at the RNA level?
missense (nonsyn), silent (syn), nonsense (nonsyn), stop
82
what do we call point mutations at the DNA level?
substitutions (transition/transversion) (syn), insertions/deletions (frameshifts) (nonsyn)
83
purine -> purine
pyrimidine ->pyrimidine
this is what kind of mutation at the DNA level?
transition
84
purine ->pyrimidine
is what kind of mutation at the DNA level?
transversion
85
silent mutations are considered _______ because they do not affect the function of the protein
neutral mutations
86
______: results in a premature stop
nonsense mutation, protein function is vastly different
87
______: base-pair substitution that results in an amino acid change (usually a result of transversion)
missense mutation
88
_____/______: result in the altering of the reading frame
insertions/deletions
89
1. promoter mutations
2. splicing mutations
3. cryptic splice sites
are all examples of ________ mutations
regulatory mutations
90
where do regulatory mutations occur?
in the non-coding region of genes (untranslated regions of mRNA)
91
_____: alter consensus sequence nucleotides and interferes with efficient transcription initiation (not making as much mRNA -> alters level of gene expression)
promoter mutations
92
_____: disrupt existing splice sites, create new ones, or activate the cryptic ones
splicing mutations
93
______: certain base-pair substitutions create new splice sites that replace or compete with the authentic splice sites in pre-mRNA processing (accidentally introduce early splice site)
cryptic splice sites
94
why are mutations important?
1. increases genetic variation
2. point mutations affect phenotypes by changing amino acid sequence
