tRNA

Question 1

why might tRNA isoacceptor shifts occur during disease pathogenesis?

Answer 1

cancer cells experience metabolic stresses. ones such as hypoxia nad oxidative stress have been shown to change specific tRNA pools

Question 2

who discovered souble RNA that ended up being tRNA?

Answer 2

Hoagladn and Zamecnik

Question 3

how many parts of the tRNA life cycle are there?

Answer 3

3

Question 4

what are the 2 types of tRNA processing before they reach their final form?

Answer 4

addition of CCA to the 3’ end and nucleoside modifications

Question 5

what perfroms the 5’ trimming of bacterial tRNAs?

Answer 5

endonuclease Rnase P

Question 6

how many regions does tRNA fold into?

Answer 6

4

Question 7

what does tRNA really do?

Answer 7

forms a link between the mRNA and the correct amino acid

Question 8

what is the anticodon segment of the anticodon loop for?

Answer 8

base pair with the codon in the mRNA

Question 9

what is the orientation of the tRNA loop?

Answer 9

The longer side is the 3’ end

Question 10

what does the free 3’ and 5’ ends base pair to form?

Answer 10

acceptor stem

Question 11

waht is the conserved trinucleotide?

Answer 11

5’-CCA-3’

Question 12

what is CCA needed for?

Answer 12

needed to maintain and repair the 3’ ends of tRNAs

Question 13

what are the characteristics of the CCA adding enzyme?

Answer 13

Does not use a template
It contains a nucleotide binding pocket that can accept CTP or ATP
The size and shape of the pocket changes depending on the 3’ end of the tRNA substrate
Plays a role in targeting unstable tRNAs for degradation
Unstable tRNAs acquire CCAs
Small RNAs with multiple CCAs are rapidly degraded

Question 14

what was the T loop named for?

where is it loacted?

Answer 14

3’ side - named for occurrence of ribothymidine and pseudouridine

Question 15

what was the D loop named for?

where is it loacted?

Answer 15

5’ side - named after dihydrouridine

Question 16

where is the wobble position?

Answer 16

5’ side of anticodon - often has inosine

Question 17

what is the hypermodified purine?

Answer 17

occurs just 3’ to prevent it from base-pairing improperly with the codon in mRNA, thereby helping to align the codon and anticodon properly - 3’ side before anticodon

Question 18

what is a wobble pairing>

Answer 18

the first 2 positions on the mRNA are read by strict watson crick base pairing with positions 2 and 3 of the anticodon, when the first position is matched to the 3rd position of the codon, non-watson crick pairs are allowed. Means you don’t really need more than 2 tRNA anticodons to decipher 4 codons