L 18

Question 1

How are eukaryotic mRNAs modified?

Answer 1

by a 5’ cap and a 3’ poly(A) tail

Question 2

All classes of RNA can be modified by what?

Answer 2

exo and endonucleolytic removal of polynucleotide sequences

Question 3

how does a single gene generate several proteins?

Answer 3

through alt mRNA splicing.

Question 4

what does the 5’ cap addition during elongation do?

Answer 4

Protects mRNA from degradation, RNAP II switch

Question 5

What does 3’ polyadenylation during elongation do?

Answer 5

Protection from nucleases

Question 6

What does splicing do during elongation?

Answer 6

it removes introns

Question 7

Mature mRNAs are transported from where to where?

Answer 7

Nucleus to cytoplasm.

Question 8

Translation starts at what end? 5’ cap or poly A 3?

Answer 8

5’ Cap

Question 9

Where does translation stop?

Answer 9

poly A 3

Question 10

What is the 5’ end of the nascent mRNA capped by?

Answer 10

capped by 7 m^7 G

Question 11

Only eukaryotes have a capped RNA, what does bacteria mRNA have?

Answer 11

5’ PPP

Question 12

Capping occurs during what process?

Answer 12

It occurs during elongation

Question 13

capping enzyme does what three steps?

Answer 13

1. Hydrolysis removes 5’ y phosphate from pre mRnA
2. Guanylation of pre mRNA through 5’ to 5’ triphosphate bridge (PPi released). GTP!
3. Methylation of guanosine base at position N7. Methyl donor is SAM

Question 14

What does SAM stand for

Answer 14

(S-adenosylmethionine)

Question 15

What does Poly A tails (3-An) addition contribute to the mRNA in the cytoplasm?

Answer 15

Contributes to stability

Question 16

mRNA processing enzymes binds to what?

Answer 16

phosphorylated CTD

Question 17

What does the capping of mRNA do?

Answer 17

marks the completion of intiation and switch to elongation

Question 18

How are most eukaryotic mRNA edited to mature transcripts?

Answer 18

by splicing,

exons are spliced from preMRNA transcripts to remove introns by a two stae reaction

Question 19

What is the lariat mechanism?

Answer 19

a mechanism to remove most introns

Question 20

What are the two steps to the Lariat mechanisms

Answer 20

1. adnosine in the intron 2_oh attacks the 5’phosphate in exon 1 to form 2,5 phosphodiester bond and lariat
2. exon 1’s free 3’OH attacks 5’ phosphate in 5’ terminal residue of exon 2 to form 3’,5’ phosphodiester bond which forms a splice junction and introns are removed

Question 21

mRNA is carried out by the SPLICEOSOME, a snRNP, what does snRNP stand for?

Answer 21

smallnuclear ribonucleoprotein

Question 22

What does the sn RNP recognize and contain?

Answer 22

5’ splice junction and contain RNAs and proteins

Question 23

What are two evolutionary advantages to gene splicing?

Answer 23

1. Allows for rapid protein evolution

2. Alt splicing permits a single transcript to encode many proteins, some in a tissue spec mode

Question 24

What is OI?

Answer 24

Osteogenesis imperfecta

Question 25

About 90 percent of indiv with OI have mutation in one of the two what genes?

Answer 25

Collagen genes COL1A1 and COL 1A2

Question 26

Some eukaryotic ribosomal RNAs can splice themselves, this is an example of what?

Answer 26

RNA catalysis (ribozyme)

Question 27

What are the most abundant macromolecules in the cell?

Answer 27

Proteins

Question 28

Vast majority of proteins are what?

Answer 28

Enzymes

Question 29

How many percentage of cell's energy can be directed toward protein synthesis?

Answer 29

90 percent

Question 30

What do most important antibiotics target?

Answer 30

Protein synthesis

Question 31

What are some necessary components to translating nucleic acids to proteins?

Answer 31

``` mRNA - the template amino acids tRNAs aminoacyl tRNA synthases ATP GTP Ribsome (small unit - decoding center, large subunit - peptidyl transferase center) initiation factors elongation factors termination factors ```

Question 32

How many possible reading frames are there in one direction?

Answer 32

three