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Genetics > Ch. 15 > Flashcards

Ch. 15 Flashcards

1
Q

The one gene, one enzyme hypothesis is based on the work of

A

Beadle and Tatum

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2
Q

Protein are polymers consisting of amino acids linked by ____ bonds. Amino acid sequence is it’s ____ structure.

A

Peptide bonds

Primary structure.

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3
Q

There are ___ amino acids total.

4 components?`

A

20

Amino group, Carboxyl Group, Hydrogen, Radial Group (Side chain)

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4
Q

Codon

A

3 nucleotides = 1 amino acid

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5
Q

Nirenberg and Matthaei’s Homopolymers

A

If you create it with use one base (ex: UUUUUUUU) and all you get is phenylalanine, than that’s what it is

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6
Q

Nirenberg and Leder’s use of tRNA

A

tRNA bring amino acids to ribosome. tRNAs have anti-coons with complimentary sequence to the codon (how they bring the appropriate amino acid) .

When mRNA with GUU added, tRNA bound to valine

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7
Q

Neirenberg’s random copolymer

A

RNAs of 2-3 different basses, which would produced a certain number of proteins. Proportions decide which bases go with what.

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8
Q

There are ___ possible codons, ___ stop codons, and thus, ___ SENSE codons (encode amino acids) .

A

64

3 stop

61 sense

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9
Q

Why is this code a degenerate code?

A

Because it has multiple physical states that have equivalent meanings. Amino acid maybe specified by more than one codon.

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10
Q

Synonymous codons

A

Codons that specify the same amino acid

Many differ only in the third position

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11
Q

Initiation Codon

A

AUG (met)

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12
Q

Termination codons

A

UAA, UAG, UGA

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13
Q

How do you explain that most organisms posses from about 30-50 different tRNAs, yet there are only 20 different amino acids in proteins?

A

Isoaccepting tRNAs: Different tRNAs that accept the same amino acid but have different anticodons.

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14
Q

Wobble hypothesis

A

1st two nucleotides bind via Watson-and Crick rules.

HOWEVER, 3rd base pairs weakly (wobble)- allows some tRNAs to pair with more than one codon on mRNA, thus 30-50 tRNAs can pair with 61 sense codons.

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15
Q 
Wobble Rules: 
C
G
A
U
I (inosine)- modified bases found in tRNA
A 
C- only with G
G- C, wobbles U
A- only with U
U- A, wobbles G
I- A, U or C
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16
Q

Through wobble, a single ______ can pair with more than 1 ______.
A) codon; anticodon
B)Group of three nucleotides in DNA; codon in mRNA
C) tRNA; amino acid
D) anticodon; codon

A

d. Anticodon, codon

17
Q

Reading Frame/Nonoverlapping

A

Although Reading frame can be read different ways, in nonoverlapping, single nucleotide may not be included in more than one codon (genetic code nearly always like this)

18
Q

How does one establish the correct reading frame?

A

Initiator codon

AUG (methionine)

Bacteria: initial amino acid is formylmethionine; unformulated methionine thereafter in the polypeptide (internal)

Eukaryotes: all methionine unformulated

19
Q

What do we mean by “the universality of the code”?

A

Each codon specifies the same amino acid in all organisms (generally)

20
Q

Translation

A

Amino acids are assembled into protein.

  1. Binding of amino acids to tRNAs
  2. Initiation
  3. Elongation
  4. Termination
21
Q

The binding of amino Acids to tRNA involves
1. Aminoacyl-tRNA synthetases and
2. tRNA charging
What is charging?

A

Charging is the act of binding the amino acid to the tRNA

22
Q

What determines the specificity between an amino acid and its tRNA

A

Individual aminoacyl-tRNA synthesis (enzymes)

23
Q

There are exactly ___ different aminoacyl-tRNA synthetase in a cell.

A

20, one for each amino acid.

24
Q 
Amino Acids bind to which part of tRNA?
A) anticodon
B) DHU arm
C) 3' end
D) 5' end
A

C) 3’ End

25
Q

The three steps of initiation of translation:

  1. mRNA binds to __________
  2. Initiator tRNA binds to the mRNA through ______________
  3. _____________ joins the initiation complex.
A
  1. mRNA binds to THE SMALL SUBUNIT OF THE RIBOSOME
  2. Initiator tRNA binds to the mRNA through BASE PAIRING BETWEEN THE CODON AND THE ANTICODON
  3. THE LARGE RIBOSOME joins the initiation complex
26
Q

The Shine-Dalgarno consensus sequence in bacterial cells is recognized by _______.

A

the Small unit of the ribosome

27
Q

The ____ sequence in eukaryotic cells facilitates the identification of the start codon

A

Kozak

5’- ACCAUGG- 3’

(AUG=start codon)

28
Q

Elongation in translation is the attachment of amino acids to form

A

polypeptides

29
Q

Three steps of Elongation

  1. Charged tRNA binds to _ ___.
  2. Formation of ____ bond between amino acids that are attached to tRNAs in the _ and _ sites.
  3. ______, the movement of ribosome down the mRNA in the 5’–>3’ direction.
A
  1. Binds to A site
  2. Peptide bond between amino acids attached to tRNAs at P&A sites
  3. Translocation
30
Q

rRNA in the large subunit of the ribosome catalyzes the peptide bond, called the ____ ________center.

A

Peptidyl Transferase center

31
Q

Polyribosomes

A

mRNA with several ribosome attached.

Becomes longer as ribosome moves along mRNA.

32
Q

mRNA is bound to ___ _____ subunit, and tRNAs are located in the _, _, and _ sites.

A

mRNA is bound to small ribosomal subunit, and tRNAs are located in the A, P, and E sites.

33
Q

Difference between timing of transcription and translation in prokaryotes vs. eukaryotes?

A

Prokaryotes: Same time

Eukaryotes: Transcription in nucleus.
translation cytoplasm

34
Q

mRNA surveillance

nonsense- mediated mRNA decay

A

Detect and deal with errors.

Nonsense-mediate mRNA decay: eliminating mRNA containing premature termination codons.

35
Q

Stalled Ribosome (prokaryotes)

A

occurs when a stop codon is missing: transfer-mRNA (tmRNA) transfers a stop codon and signal for degration

36
Q

No-go decay

A

removes stalled ribosomes

37
Q

What helps some proteins fold correctly?

A

Molecular Chaperones

38
Q

What helps direction protein to specific location through modification of some proteins (the removal of 15-30 amino acids) called the ____ ____ at amino end of protein.

A

Signal Sequence

39
Q

Why is translation often the target of antibiotics?

A

Translation differs between bacterial and eukaryotic cells.

Genetics (15 decks)

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