Lecture 24 - RNA processing

Question 1

mRNA in eukaryotes is modified after

Answer 1

transcription

Question 2

A poly (A) tail prevents

Answer 2

digestion of mRNA by exonucleases in the cytosol

Question 3

In bacteria, polypeptide chains are encoded by

Answer 3

a continuous DNA sequence

Question 4

In RNA splicing, the introns are ________ and the exons are ________ to form the mature mRNA

Answer 4

excised; linked

Question 5

The _______ is 20-50 nucleotides upstream of the 3’ splice site

Answer 5

branch site

Question 6

The splicing process is done by a large complex called the

Answer 6

spliceosome

Question 7

The spliceosome consists of both

Answer 7

RNAs and proteins

Question 8

The chemistry of the splicing process consists of two sequential transesterification reactions

Answer 8

1. Cleavage of the phosphodiester bond between upstream exon (exon 1) and 5’ end of the intron
2. The 3’-OH terminus of exon 1 attacks the phosphodiester bond between the intron and exon 2

Question 9

In the lariat intermediate, the adenylate residue is joined to

Answer 9

three nucleotides by phosphodiester bonds

Question 10

A group of small nuclear RNAs (snRNAs) are essential for

Answer 10

splicing

Question 11

The snRNAs essential for splicing are called

Answer 11

U1, U2, U4, U5, and U6

Question 12

snRNAs form complexes with specific proteins that together are referred to as

Answer 12

small nuclear ribonucleoprotein particles (snRNPs)

Question 13

Splicing begins with the recognition of the 5’ splice site by the

Answer 13

U1 snRNP

Question 14

U2 snRNP binds the branch site by

Answer 14

base-pairing between a sequence in U2 snRNA and the pre-mRNA

Question 15

A preassembled _______ joins the U1-U2 complex to form the spliceosome

Answer 15

U4-U5-U6 tri-snRNP

Question 16

Alternative splicing is a mechanism for generating

Answer 16

protein diversity

Question 17

Most alternative splicing leads to

Answer 17

changes in the coding sequence

Question 18

Mutations in the pre-mRNA or the splicing factors can result in

Answer 18

defective splicing