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Genetics > Chapter 13 The Genetic Code and Transcription > Flashcards

Chapter 13 The Genetic Code and Transcription Flashcards

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Biology 101 flashcards
1
Q

The genetic code is…

A

written

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2
Q

mRNA molecules act as …

A

letters

They have complementary bases

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3
Q

Triplet codons…

A

specify one amino acid (mRNA)

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4
Q

Unambiguous

A

triplet= 1 amino acid

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5
Q

Degenerate

A

amino acid specified by more than 1 triplet

“start” and “stop” signals

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6
Q

The genetic code is…

A 
unambiguous
degenerate
one start and three stop
nonoverlapping
nearly universal
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7
Q

Jacob and Monad-

Early studies establishing basic operational patterns of the genetic code

A

1961- hypothesized mRNA

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8
Q

What is mRNA?

A

intermediate in transferring genetic information

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9
Q

How can 4 nucleotides encode 20 amino acids?

A

triplet code

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10
Q

Triplet nature of the code…

A

64 codons specify 20 amino acids

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11
Q

Reading frame…

A

sequence of nucleotides encoding a polypeptide

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12
Q

Crick and colleagues:

A

acridine dye- induce DNA mutations into a T4 phage

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13
Q

Frameshift mutations…

A

change reading frame

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14
Q

Brenner and colleagues - nonoverlapping code

A

-genetic code reads 3 nucleotides at a time in a continuous, linear manner

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15
Q

During translation, the genetic code is…

A

nonoverlapping

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16
Q

Nirenberg and Matthei

A

characterize coding sequences

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17
Q

Nirenberg and Matthei utilized…

A
  • in vitro protein synthesizing system

- polynucleotide phosphorylase- enzyme- artificial synthesis of RNA templates- does not require DNA template

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18
Q

RNA homopolymer

A

one type of mRNA

used UUUU…., AAAA…., CCCC…., or GGG to determine which amino acids were incorporated into the proteins

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19
Q

Attached _____ to a different amino acid in each experiment

A

14C

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20
Q

GGG is a …

A

non funcional template

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21
Q

In mixed copolymers the proportion known, could predict…

A

the frequency of possible triplets

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22
Q

mixed copolymers predict…

A

composition of triplets

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23
Q

Triplet binding assay consists of…

Nirenberg and Leder

A
  • Ribosomes (bind to single codon of 3 nucleotides)
  • codon
  • complementary amino acid- charged tRNA (radioactive) termed anticodon
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24
Q

Triplet binding assay…

Incubate what???

A
  • radioactive tRNA
  • RNA triplet
  • nitrocellulose filter with ribosomes
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25
Q

If the paper is NOT radioactive???

A

incorrect AA was tested; repeat experiment

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26
Q

If the paper is radioactive???

A

tRNA bound to RNA triplet associated with ribosome

A specific codon assignment is made

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27
Q

What are repeating copolymers?

A
  1. chemically synthesized long RNA’s
  2. short repeating sequences enzymatically joined short sequences together, which made long RNA’s
  3. used for in vitro translation to determine more codon assignments
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28
Q

Repeating copolymers are dependent on…

A

initiation point

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29
Q

Coding Dictionary is ___________ meaning many amino acids are specified by more than one codon

A

degenerate

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30
Q

How many termination signals are there?

A

3

UAA UGA UAG

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31
Q

how many triplet codons are there for amino acids

A

61

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32
Q

What is the Wobble hypothesis

A

The first 2 ribonucleotides of triplet codes are more critical than the 3rd because the third position is less spatially constrained.
H bonding is more relaxed at the 3rd position
anticodon pair with more than one mRNA triplet

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33
Q

Ordered nature of code

A

similar AA often share middle bases in the coding triplets

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34
Q

In translation initiation, the initial __ is incorporated

A

AA

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35
Q

what is the initial AA?

A

modified form of methionine- N- formylmethionine (fmet)

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36
Q

What is the codon?

A

AUG

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37
Q

internally in mRNA, __________ methionine is inserted

A

unformylated

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38
Q

What are termination codons?

A

UAG UAA UGA

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39
Q

The termination codons are not recognized by ____ molecule

A

tRNA

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40
Q

What does termination end?

A

translation

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41
Q

what is a nonsense mutation?

A

mutation to stop codon internally in a gene may lead to early termination
This causes a partial peptide

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42
Q

codon UGA normally specifies termination, but in mtDNA, UGA codon encodes_________ in yeast and humans

A

tryptophan

43
Q

codon UAU normally specifies isoleucine, but in human mitochondria it encodes internal insertion of ______________

A

methionine

44
Q

Different initiation points creates __________ genes

A

overlapping

45
Q

ORF (open reading frame(overlapping genes))???

A

DNA sequence produces RNA with start and stop

Series of triplet codons specify amino acids to make polypeptides

46
Q

In some viruses, initiation at different AUG positions out of frame with another leads to distinct____________________

A

polypeptides
Ex: X174- expected 1795 aa; 9 proteins
(where there would have only been 3, there are now 7)

47
Q

Transcription Synthesis; RNA on a DNA template

4 things…

A
  1. Where is DNA? Where is protein synthesis?
  2. List commonalities between DNA and RNA.
  3. After RNA synthesis, it migrates to cytoplasm
  4. # RNA is generally proportional to # protein in a cell
48
Q

RNA serves as an _______________ molecule between DNA and proteins

A

intermediate

49
Q

RNA is synthesized on a ___ template

A

DNA

50
Q

RNA polymerase directs RNA synthesis using a ___ template

A

DNA

51
Q

RNA polymerase directs RNA synthesis with/ without a primer???

A

without

52
Q

RNA polymerase uses __________________ instead of deoxyribonucleotides

A

ribonucleotides

53
Q

Reaction for RNA synthesis can be expressed as…

A

nNTP+NTP—–DNA—–(NMP)n+n(PPi)

54
Q

What are the e coli subunits for RNA polymerase?

A

alpha, beta, beta prime, and sigma

55
Q

Which e coli subunits are the active sites for transcription?

A

beta and beta prime

56
Q

what is the sigma factor?

A

regulatory function in the initiation of RNA transcription

57
Q

In transcription, RNA polymerase binds to a __________________

A

promotor

58
Q

Which subunit is responsible for promotor recognition?

A

sigma

59
Q

Where does transcription begin?

A

transcription start site

60
Q

The DNA is __________ to make the template strand accessible

A

unwound

61
Q

Promotors have 2 consensus sequences. What are they?

A

TTGACA

TATAAT

62
Q

Where are the 2 consensus sequences positioned?

A

-35 and -10 to the initiation site

63
Q

Mutations? Increase or decrease?

A

decrease

64
Q

cis- acting elements are… _________________ to start site

A

adjacent

65
Q

In transcription chain elongation - nucleotides are synthesized, and sigma subunit_______________

A

8-9

dissociates

66
Q

____________ proceeds with the core enzyme

A

elongation

67
Q

continues to transcribe until ______________

A

termination

68
Q

In transcription termination, RNA hairpin formation is held by what bonds?

A

hydrogen

69
Q

Can depend on the rho (p) termination factor… what is this?

A

large hexameric protein that interacts with RNA

70
Q

Transcribed RNA is ______________. It is complementary to DNA, yet will contain _ instead of T.

A

released

U

71
Q

Eukaryotic vs. Prokaryotic transcription:

Eukaryotes: occurs in the _________ and is not coupled to translation (move to cytoplasm)

A

nucleus

72
Q

Eukaryotic vs. prokaryotic transcription:

chromatin _______________

A

remodeling

73
Q

eukaryotic vs. prokaryotic transcription:

involves __________

A

enhancers

74
Q

eukaryotic vs. prokaryotic transcription:

mRNAs require processing 5’ _______ and 3’ ________

A

cap

tail

75
Q

RNA polymerase in eukaryotes:
Form: 1
Product: _______
Location: nucleolus

A

rRNA

76
Q

RNA polymerase in eukaryotes:
Form: 2
Product: ____, _______
Location: nucleoplasm

A

mRNA, snRNA

77
Q

RNA polymerase in eukaryotes:
Form: 3
Product: _______,_____________
Location: nucleoplasm

A

5S rRNA, tRNA

78
Q

RNA polymerase 2 promoters contain:

2 things

A
  • a core promoter element where protein binds and transcription begins
  • promoter and enhancer elements that determine rate of transcription
79
Q

What is a TATA box? (Goldberg- Hogness)

A
  • core promoter element
  • (-30) TATA A/T AAR (A or T in 5th position)
  • TATA binding protein (TBP)
  • start site of transcription
80
Q

What is the CAAT box in RNA polymerase 2?

A

upstream and part of eukaryotic promoter

81
Q

enhancers and silencers are found ____, ________, or ____________ of a gene

A

upstream
within
downstream

82
Q

enhancers ________ transcription levels, silencers ________ them

A

increase

decrease

83
Q

enhancers and silencers _______ transcription from a distance

A

modulate

84
Q

enhancers and silencers act to ________ or ________ transcription in response to cell’s requirement for ____ product

A

increase
decrease
gene

85
Q

Transcription factors facilitate _____ binding and __________ of transcription

A

RNAP 2

initiation

86
Q

General transcription factors are ________ for all RNAP 2 mediated transcription

A

required

87
Q

Transcription activators and repressors…

A

influence efficiency or rate of RNAP2 transcription initiation

88
Q

RNA PROCESSING:

5’ cap protects from _________, helps transport across nuclear membrane into _________.

A

nucleases

cytoplasm

89
Q

RNA PROCESSING

The RNA tail is the _________ cap. The 3’ region is _______ in UAUCAA region, then polyadenylation occurs

A

following

cleaved

90
Q

What are intervening sequences?

A

introns and exons

91
Q

What is an intron?

A

an intervening sequence where regions of initial RNA transcript is not expressed in amino acid sequence of protein
DNA sequences are not represented in final mRNA product

92
Q

What is an exon?

A

an intervening sequence where the sequence in retained and expressed.

93
Q

What is a heteroduplex?

A

introns present in DNA but not mRNA that loop out

94
Q

introns are removed by ________

A

splicing

95
Q

exons are joined together and called ______ mRNA

A

mature

96
Q

SPLICEOSOME

splices out pre- ____ introns

A

mRNA

97
Q

What is essential for the spliceosome?

A

small nuclear ribonucleoproteins (snRNP’s)

98
Q

what is the donor sequence?

A

GU

99
Q

what is the acceptor sequence?

A

AG

100
Q

The “loop” is called a ______ structure

A

lariat

101
Q

There are ___ transesterfication reactions

A

2

102
Q

At the end… the exons are _______

A

ligated

103
Q

What is substitution editing?

A

identities of individual nucleotide bases are altered; prevalent in mitochiondria and chloroplasts RNA derived in plants

104
Q

What is insertion/ deletion editing?

A

nucleotides are added/ deleted from total number of bases

prevalent in mitochondrial and chloroplast RNA’s

Genetics (3 decks)

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