07b: Protein Synthesis Flashcards Preview

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Flashcards in 07b: Protein Synthesis Deck (40):
1

How many bases in tRNA for euk? And prok?

Same for both: 75 bases

2

What percent of bases in tRNA are base paired?

50%

3

(X)% of bases in tRNA are modified.

X = 10

4

All tRNA molecules have which base sequence at the (5'/3') end?

CCA at 3' end

5

Where on (X) molecule is the site of AA charging?

X = tRNA

at 3' end

6

Which loops are present in tRNA?

1. D loop
2. Anticodon loop
3. T loop

7

Function of tRNA D loop

Recognized by synthetase enzymes

8

Function of tRNA T loop

Interacts with 5S rRNA (helps position tRNA in ribosome)

9

The (X) sequence always present at the (3'/5') end of tRNA is (transcribed/added post-transcriptionally).

X = CCA

3' end

Either encoded or added post-transcriptionally

10

The 3D structure of tRNA shows that it has which shape?

L-shape

11

(Prok/euk) tRNA are multimeric, which means:

Prokaryotic; 2 or more tRNA per transcript

12

T/F: Bacterial tRNA transcripts may be embedded in rRNA transcripts.

True

13

Steps to Bacterial tRNA transcript processing:

1. RNases cleave 5' then 3' ends
2. Bases modified
3. CCA added to 3' end

14

(Prok/euk) tRNA are monomeric, which means:

Eukaryotic;

Only 1 tRNA per transcript

15

What are the key differences, if any, between euk and prok tRNA?

1. Euk monomeric precursor and prok multimeric
2. Intron in anticodon loop of euk tRNA

16

What's the reason for the (intron/exon) in the (X) loop of (prok/euk) tRNA?

Intron
X = anticodon
Eukaryotic

So that tRNA precursor can't be used in protein synthesis prematurely

17

Removal of tRNA (X) in anticodon loop, activating the tRNA, involves:

X = intron

1. Endonuclease cleavage
2. ATP-dependent ligation

18

How many precursors does it take to synthesize all 3 bacterial rRNAs?

One large precursor

19

Describe the processing of bacterial rRNA from precursor.

RNase III cleaves double-stranded regions of RNA in an asymmetric manner (leaving 2 base 3' overhang)

20

Euk rRNA synthesis is done by:

RNA Polymerase I

21

Eukaryotic rRNA precursors are transcribed from (highly/moderately/single)-repetitive sequences.

Moderately

22

Is there post-transcriptional processing of eukaryotic rRNA?

Yes - self-splicing of 45S rRNA precursor

23

T/F: All euk rRNA are transcribed by the same protein.

False - 5S rRNA transcribed by RNA Pol III (rest by Pol I)

24

Where does transcription of 5S rRNA take place?

Nucleus

25

Where does transcription of most euk rRNA take place?

nucleolus (except 5S rRNA)

26

Where does assembly of the individual ribosomal subunits take place in euk?

Nucleolus (5S rRNA and ribosomal proteins go into there to assemble)

27

What are the organelles of protein synthesis?

Ribosomes

28

List the characteristics of the genetic code.

1. Degenerate
2. Non-ambiguous
3. Almost universal (except mitochondria)

29

Genetic code is degenerate means:

more than 1 codon for some AAs

30

Genetic code is non-ambiguous means:

only 1 AA for each codon

31

A point mutation is:

single base change

32

A silent mutation is:

Change that specifies the same AA

33

Missense mutation is:

Change that specific different AA

34

Nonsent mutation is:

Change that produces STOP codon

35

Which changes can cause frameshift?

Addition/deletion of 1 or 2 bases

36

The anticodon on (X) interacts with codon on (Y) in (Z) fashion

X = tRNA
Y = mRNA
Z = antiparallel

37

The sequences of (codons/anticodons) are given 5' to 3'.

Both!

38

What's the sequence of the anticodon that would base pair with codon UCA?

UGA

39

Wobble indicates flexibility with:

3' Base Codon

40

According to wobble, (X) can base pair with a number of different (Y).

X = 5' base anticodon
Y = 3' base codon