biochem 7A - RNA structure, syntehsis, and processing

Question 1

Which RNA
-smallest (4S) of the 3 major types of RNA
-at least one specific type of tRNA for each of the 20 aa
-comprise about 15% of RNA in cell
-carries its amino acid on 3’ end, to the site of protein synthesis

Answer 1

transfer RNA

Question 2

messenger RNA function

Answer 2

-carries genetic information from the nuclear DNA to cytosol, where it is used as the template for protein synthesis

Question 3

has a long sequence of adenine nucleotides (poly A tail) on the 3’ end and also a cap on the 5’ end consisting of a molecule of 7-methylguanosine attached via triphosphate linkage

Answer 3

messenger RNA

Question 4

what is the multisubunit enzyme that recognizes a nucleotide sequence (promoter) at the beginning of the length of DNA to be transcribed

Answer 4

RNA polymerase

Question 5

sense strand / coding strand

Answer 5

DNA strand w the same sequence as the mRNA

Question 6

antisense strand

Answer 6

DNA strand that is being transcribed into mRNA

Question 7

what direction does prokaryotic transcription happen

Answer 7

5’-3’

Question 8

does RNA polymerase need a primer?

Answer 8

no

Question 9

what direction does the RNA strand grow

Answer 9

5’-3’

Question 10

the RNA polymerase proceeds along which DNA strand

Answer 10

anti-sense strand

Question 11

Rho independent termination

Answer 11

stem loop structure signals release of mRNA

Question 12

rho dependent termination

Answer 12

mRNA pulled away from RNA polymerase

Question 13

actively transcribed genes are found in what form of chromatin

Answer 13

relaxed form (euchromatin)

Question 14

most inactive segments of transcribed genes are found in what form of chromatin

Answer 14

condensed form (heterochromatin)

Question 15

what is chromatin remodeling

Answer 15

when chromatin changes from the relaxed form to the condensed form vise versa

Question 16

what is a major mechanism of remodeling

Answer 16

acetylation of lysine residues

Question 17

what catalyzes acetylation

Answer 17

histone acetyltransferases (HAT)

Question 18

what catalyzes deacetylation

Answer 18

histone deacetylases (HDAC)

Question 19

RNA polymerase I

Answer 19

synthesize the precursor of the 5.8S, 18S, and 28S rRNA in the nucleolus

Question 20

RNA polymerase II

Answer 20

syntehsize mRNA

Question 21

RNA polyermase III

Answer 21

synthesize tRNA and 5S rRNA

Question 22

mitochondrial RNA polymerase

Answer 22

transcribes RNA from all mitochondrial genes

Question 23

RNA processing in prokaryotes vs eukaryotes

Answer 23

in prokaryotes - RNA is used as unaltered primary transcript as soon as it is made

in eukaryotes - capping at 5’ end, addition of poly(A) tail at 3’ end, removal of introns

Question 24

what happens in RNA capping and reason

Answer 24

7-methylguanosine cap at the 5’ end of the mRNA linked to the 5’ ribose via triphosphate linkage

cap protects the 5’ end from exonucleases and promotes mRNA translation by ribosomes

Question 25

addition of poly-A-tail reason

Answer 25

-40-200 adenine nucleotides attached to 3’ end
-not transcribed from DNA but added after transcription
-helps to stabilize the mRNA
-facilitates the mRNA exit from nucleus and aid in translation
-gradually shortened after entering the cytosol

Question 26

what catalyzes the addition of poly-A-tail

Answer 26

polyadenylate polymerase