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genetics > chapter 9 part 2 > Flashcards

chapter 9 part 2 Flashcards

1
Q

start codon

A

AUG - methionine

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2
Q

stop codons

A

UAA. UAG, UGA

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3
Q

kinase

A
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4
Q

what are release factors

A

ALL organisms use these to bind a stop codon in the A-site, which then makes the polypeptide bond to the tRNA at the P-site release & the RF is ejected- then ribosomal subunits separate

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5
Q

what are the release factors in bacteria

A

-RF1: recognize UAG & UAA
-RF2: recognize UGA & UAA
-RF3: recycles RF1

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6
Q

what is the release factor in eukaryotes & archaea

A

-eRF1 recognizes all three stop codons
-eukaryotes have a second release factor that recycles eRF1

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7
Q

how many ribosomes do bacteria cells contain & how much percent of the cell mass do they make up?

A

-20,000
-25%

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8
Q

what are polyribosomes

A

structures containing groups of ribosomes all actively translating the same mRNA

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9
Q

where are mRNAs produced in eukaroytes?

A

the nucleus
-must be processed to form mature mRNAs & then exported to the cytoplasm for translation

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10
Q

is monocistronic in eukaroytes or prokaryotes

A

eukaryotes

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11
Q

monocistronic

A

an RNA that directs synthesis of a single kind of polypeptide

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12
Q

what produces polycistronic mRNAs in bactera

A

operons

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13
Q

what are polycistronic mRNAs?

A

these lead to the synthesis of several different proteins
-contain more than one polypeptide-producing segment
-each segment has a start & stop codon
-most segments have shine-delgarno sequences

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14
Q

what separates the segments is polycistronic mRNA

A

intercistronic spacer sequences

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15
Q

are intercistronic spacer sequences translated?

A

no!

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16
Q

when can intact ribosomes proceed to the next start codon after finishing translation of the previous segment without disassembly

A

when the intercistronic spacer is short

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17
Q

transfer RNAs

A

adaptor molecules that interpret & then act on infromation carried in mRNA

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18
Q

codons

A

groups of three consecutive nucleotides in an mRNA each correspond to one amino acid

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19
Q

how many codons does to genetic code contain?

A

64

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20
Q

what are synonymous codons?

A

code for the same amino acids (ex: ser has seven different codons)

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21
Q

how many different tRNA genes do most genomes have?

A

30-50

22
Q

isoaccepting tRNAs

A

tRNA molecules with different anticodons that carry the same amino acid

23
Q

is genetic code universal?

A

yes, in fact bacteria can be used to produce important proteins from plants & animals

24
Q

what are aminoacyl-tRNA synthetases or tRNA synthetases

A

enzymes that catalyze the addition of the correct amino acid to tRNAs

-a large molecule that contacts several points on the tRNA in the recognition process

25
Q

acceptor stem

A

the correct tRNA fits into the active site of the tRNA synethetase

26
Q

what provides energy for the tRNA synethetase attachment of amino acid

A

ATP

27
Q

who determined that an overlapping genetic code was no possible?

A

sidney brenner

28
Q

what did fraenkel-conrat find?

A

single nucleotide changes led to a single amino acid change

29
Q

how did we get proof of a triplet genetic code?

A

when researchers created mutations by insertion or deletion of single nucleotides into the rII gene in T4 bacteriophage

30
Q

what is the reading frame?

A

this refers to the specific codon sequence as determined by the start codon

31
Q

what are frameshift mutations?

A

mutations that alter the reading frame
-all the codons after the addition or deletion will specify the wrong amino acids

32
Q

what are the two categories of post-translational events

A

-post-translational polypeptide processing
-protein sorting

33
Q

Post-translational polypeptide processing

A

-modifies polypeptides into functional proteins by removal or chemical alteration of amino acids

34
Q

protein sorting

A

-uses signal sequences/leader sequences to direct proteins to their cellular destinations

35
Q

is fMet found in functional bacterial proteins?

A

no

36
Q

T/F: methionine is always the first amino acid in eukaryotic proteins

A

False

37
Q

what is the most common amino acid modification?

A

phosporylation

38
Q

what is phosphorylation?

A

it is carried out by kinase enzymes that add phosphates to proteins
it can activate or inactivate a protein

39
Q

what are other enzymes that may add other functional groups to amino acids?

A

methyl- methylase
hydroxyl- hydroxylase
acetyl- acetylase

-carbohydrate side chains are also added to some proteins

40
Q

insulin

A

-first produced as proproinsulin
-cleaved at the N-terminus to proinsulin
-cleaved again after froming disulfide bonds to make insulin

41
Q

what does insulin consist of?

A

A-chain & B-chain segments

42
Q

what do signal sequences do?

A

-15 to 20 amino acids at the N-terminal direct proteins to their cellular destinations

43
Q

what is the signal hypothesis?

A

proposes that the first 15 to 20 amino acids of many polypeptides contain an “address label”

44
Q

what did Blobel suggest?

A

that the signal sequence directs proteins to the endoplasmic reticulum (ER) & then the Gogli Apparatus, where they are sorted for their specific destinations

45
Q

what do proteins destined for the ER have?

A

a N-terminal signal sequence that direct the forming polypeptide into the ER lumen or membrane

46
Q

where are polypeptides destined for secretion produced?

A

at the rough ER

47
Q

transmembrane proteins

A

Cotranslation of proteins into the ER lumen are deposited within the membrane itself

48
Q

conformational diseases

A

-when large amounts of mutant proteins accumulate
-often neurodegenerative disorders & dementias

49
Q

types of conformational diseases

A

-alzheimer disease
-parkinson’s disease (a form of it)
-huntington’s disease

50
Q

Most synonymous codons can be grouped so they differ only in ____ _____ ____.

A

the third base

51
Q

what does the third base wobble create

A

flexible pairing at the 3’ nucelotide of the codon

genetics (37 decks)

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