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Genetic Analysis I > 9.1-9.2 > Flashcards

9.1-9.2 Flashcards

1
Q

Genetic code is the language that allow

A

DNA and RNA sequences to be
translated into proteins

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2
Q

Two nucleotides

A

4^2 = 16 possible codons

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3
Q

how many amino acids

A

20

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4
Q

codon

A

nucleotide triplet

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5
Q

code is partically

A

redunant more than one codon per given AA

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6
Q

Charles Yanofsky and Sydney Brenne

A

in 1960s, collected evidence that supported gene-protein colinearity
1. The length of the gene is proportional to the length of the protein
2.Consecutive nucleotides in a gene from the start to stop determine the consecutive/linear order of amino acids in a protein

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7
Q

Yanofsky and his lab generated a set

A

Trp- auxotrophic mutants in E. coli

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8
Q

Trp- auxotrophic mutants in E. coli

A

Mutations in trpA gene, encoding a subunit of the enzyme tryptophan synthase

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9
Q

Trp- auxotrophic mutants in E. coli

A

Mutations in trpA gene, encoding a subunit of the enzyme tryptophan synthase

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10
Q

Yanofsky was the first to

A

Created a fine-structure recombination map of these mutations using P1 bacteriophage and determined the amino acid sequence of the mutant tryptophan synthase

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11
Q

Point mutations altering different nucleotides may affect the

A

SAME amino acid (missense mutations)

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12
Q

A Gene’s Nucleotide Sequence is

A

Colinear with the Amino Acid Sequence of the Encoded Polypeptide

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13
Q

Francis Crick and Sydney Brenner

A

In 1955, used bacteriophage T4 rIIB gene with Proflavin mutation

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14
Q

Missense mutation

A

mutation in gene that changes a codon for one amino acid to a codon that specifies a different amino acid

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15
Q

Yanofsky observed

A

missense mutation

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16
Q

Francis Crick and Sydney Brenner proved

A

codons are 3 nuclotides

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17
Q

proflavin molecules cause

A

single base insertions or deletions (frameshift mutation)

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18
Q

In vitro Translation System

A

cellular extracts that upon addition of mRNA
can lead to polypeptide synthesis in a test tube

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19
Q

Marshall Nirenberg and Heinrich Matthaei

A

In 1961, added a synthetic poly-U (5’…
UUUUUUUUUU…3’) mRNA to cell-free
translational system derived from E.coli.

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20
Q

deciphering the genetic code

A

Nirenberg, Khorana and Holley

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21
Q

In 1965, Nirenberg and Philip Leder

A

added short synthetic mRNA ONLY 3
nucleotides in length to an in vitro translational
system containing tRNA attached to amino acids,
where only 1 of the 20 amino acids was
radioactive

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22
Q

Nirenberg and Philip Leder

A

Codon-amino acid correspondences

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23
Q

“STOP” codons

A

UGA, UAA and UAG

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24
Q

Sydney Brenner

A

indentified stop codons

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25
Q

Sydney Brenner used

A

Point mutations in T4 phage head protein “m”, encoding a component
of phage head capsule

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26
Q

nonsense mutation

A

changes a codon
that signifies an amino acid (a sense
codon) into one that does not (STOP CODON)

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27
Q

5’ to 3’ in mRNA corresponds to

A

N to C-terminus in the polypeptide

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28
Q

Proteins are encoded by

A

non-overlapping triplets of nucleotides called codons in a given
gene

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29
Q

initiation codon, AUG

A

codes for methionine at the start of the
reading frame

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30
Q

The genetic code is

A

degenerate

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31
Q

The three stages of transcription

A
  1. Initiation
  2. Elongation
  3. Termination
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32
Q

Transcription is carried out by

A

RNA polymerases

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33
Q

Initation

A

DNA sequences at the beginning of genes called “promoters” direct the exact location for the initation of transcription by RNA polymerase

34
Q

What is required for initiation

A

sigma factor

35
Q

Core enzyme + sigma =

A

holoenzyme (RNA polymerase)

36
Q

sigma factor

A

reduces RNA polymerase’s general affinity for DNA but increases the enzyes affinity for the promoter (binds tighty) and forms closed promoter complex

37
Q

Open promoter complex

A

RNA polyerase and unwound promoter

38
Q

Elongation

A

Constructing an RNA copy of the gene RNA poly slides along the DNA to synthesize RNA

39
Q

Elongation rate

A

50 nucleotides per sec

40
Q

Once an RNA poly moves way from promoter

A

a second RNA poly can bind the promoter and initiate transcription

41
Q

A can express different genes at

A

different rates

42
Q

Termination

A

a terminator is reached that RNA poly and RNA transcipt to dissociate from DNA

43
Q

Intrinsic terminators

A

cause RNA poly to terminate transciption on its own

44
Q

Extrinsic terminators

A

require addition proteins (Rho protein)

45
Q

Transciption has many

A

initiator sites

46
Q

Transcription uses ___ for energy

A

NTPs

47
Q

Only small portion of DNA is

A

transcipted

48
Q

AIDS uses

A

reverse transciption

49
Q

eukaryotic RNA poly II

A

transcribes genes that encode proteins

50
Q

reverse transcription

A

reverse transciptase synthesizes DNAstrands complementary to an RNA template

51
Q

reverse transcription product

A

cDNA

52
Q

RNA processing

A

in eukaryotes, converts RNA into mRNA

53
Q

Modification for mRNA

A

splicing exons (removing introns), and addition of a poly-A tail to the 3’ end and a methylated cap at the 5’ end

54
Q

Methylated cap

A

crucial for efficient translation of mRNA to protein

55
Q

poly-A tail

A

consisting of 100-200 A resiues, that stabilizes the mRNA and increases the efficiency of translation initiation

56
Q

Eukaryotes use ___ that bind to protein factors aiding transciption

A

enhancer

57
Q

basal transcription

A

core promoter by itself produces low level of transcription

58
Q

Regulatory elements

A

affect the binding of RNA poly to the promoter
1. Enhancer: stim. transcription
2. Silencers: Inhibit transciption

59
Q

RNA poly I

A

rRNA

60
Q

RNA poly III

A

tRNA

61
Q

Methy transferases

A

add methy (-CH3) groups to backward G
m7G meth cap

62
Q

Poly-A tail length

A

100-200 As long

63
Q

Translation initiation factors bind to

A

methylated cap, while poly-A binding
proteins associate with the 3’ poly-A tail

64
Q

Enhances translation

A

initiation

65
Q

DNA nucleotide seq of many eukaryotic
genes are much longer than corresponding
mRNA

A

we remove introns

66
Q

human gene DMD

A

encodes the protein Dystrophin and mutation can cause Duchenne Muscular Dystrophy

67
Q

Exons (for expressed regions):

A

Sequences found in both a gene’s DNA
and mature mRNA

68
Q

RNA Splicing:

A

The process that deletes introns and
joins together successive exons to
form mature RNA

69
Q

Splicing requires a complicated intranuclear machine

A

Spliceosome

70
Q

Spliceosome consists of four subunits called

A

Small nuclear ribonucleoproteins OR snRNPS

71
Q

Each snRNP contains

A

1 or 2 small nuclear RNAs
(snRNAs

72
Q

snRNP

A

-100-300 nucleotides long associated
with proteins in discrete particle.

73
Q

Splicing is catalyzed by

A

splicesome

74
Q

Ribozymes

A

RNA molecules that can act as enzymes to catalyze specific reactions (splice themselves) have 5 snRNAs

75
Q

alternative splicing

A

production of different mature mRNAs from the same primary RNA by joining different combinations of exons

76
Q

Alternative splicing largely explains how

A

28,000 genes in the human genome can encode hundred of thousands different proteins

77
Q

Alternative splicing can regulate

A

localization of proteins and their enzymatic properties.

78
Q

isoforms

A

Proteins resulting from alternative splicing

79
Q

Introns allow for

A

alternative splicing

80
Q

Introns can generate

A

non-coding RNAs (ncRNA) that influence gene expression

81
Q

snRNA

A

components of slocesome which is required for RNA splicing

Genetic Analysis I (9 decks)

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