LT6: RNA processing

Question 1

What’s the most abundant RNA?

Answer 1

Ribosomal RNA

Question 2

Who synthesizes pre-rRNA

Answer 2

RNA polymerase I

Question 3

Pre-RNA is processed where and to generate what

Answer 3

In the nucleolus

Generates the 28S, 18S, and 5.8S

Question 4

In the processing of rRNA, it is cleaved by who?

Answer 4

It’s cleaved by ribonucleases (RNase)

Question 5

In the processing of pre-rRNA, it is trimmed by….

Answer 5

Exonucleases

Question 6

In the processing of pre-rRNA l, base and sugar modification is carried out by…..

Answer 6

Small nucleolar RNAs (snoRNA)

Question 7

In transfer RNA, a 16 nucleotide sequence is cleaved by…

Answer 7

RNase P (ribozyme)

Question 8

In transfer RNA, a 14 nucleotide intron in the anticodon loop is removed by….

Answer 8

Nucleases

Question 9

In tRNA, uracil residues at the 3’end are replaced by what sequence

Answer 9

The CCA sequence

Question 10

Where can you find the CCA sequence

Answer 10

It’s found in all mature tRNA

Question 11

What does RNA polymerase II synthesizes

Answer 11

It synthesizes the primary RNA transcript called heterogeneous nuclear RNA (hnRNA)

Question 12

What does the hRNA undergoes in the nucleus

Answer 12

Undergoes extensive co-post transcriptional modification

Question 13

The modifications that hRNA undergoes in the nucleus are

Answer 13

1. 5’capping
2. 3’ poly A tail addition
3. Removal of introns (splicing)

Question 14

What is the component of “cap”

Answer 14

7-methylguanosine

Question 15

Where is cap added

Answer 15

It’s added backward in a 5’-5’ triphosphate linkage

Question 16

Addition of GMP IN cap is by who?

Answer 16

Guanylytransferase

Question 17

Cap methylation is catalyzed by..

Answer 17

Guanine -7 methyltranferase

Added to the nitrogen #7

Question 18

What are the function of capping

Answer 18

1. Aids in mRNA stabilization

2. Facilitates initiation of translation

Question 19

What is the polyadenylation signal sequence

Answer 19

AAUAAA

Question 20

What is cleaved after the PSS siganl

Answer 20

The Hn- mRNA

Question 21

The 40-200 adenine (A) nucleotide are added to which end

Answer 21

Added to the 3’end

Question 22

The A nucleotide are catalyzed by…

Answer 22

Polyadenylate polymerase (poly A pol)
-atp is used as a substrate

Question 23

The poly A tail sequence is not transcribed from where

Answer 23

From the DNA

Question 24

What are the function of the addition of 3’poly A tail

Answer 24

1. Facilitates mRNA transport out of the nucleus
2. Stabilizes the mRNA
3. Aids in translation

Question 25

What is splicing

Answer 25

It’s the removal of introns (non-coding sequence) and joining of exons (coding sequence) to form the mature mRNA

Question 26

What is the structure of intron

Answer 26

• 5’ splice site : 5’ GU 3’
• 3’ splice site : 5’ AG 3’
• branch point A

Question 27

In any kind of mRNA, whenever there’s an intron, it always start with what and ends with what

Answer 27

• Starts with GU
• ends with AG
• has a branch site in the middle

Question 28

What are the 2 mechanisms of splicing

Answer 28

SnRNPs

The splicesome

Question 29

What does snRNPs stands for

Answer 29

Small nuclear ribonucleoprotein

Question 30

SnRNPs consists of

Answer 30

Small nuclear RNAs (snRNA) associated with nuclear proteins

Question 31

SnRNPs aids in what?

Answer 31

They aid in splicing

Question 32

What is the molecular complex that accomplishes the splicing mechanism

Answer 32

The spliceosome

Question 33

How many % of all genetic diseases are a result of mutations that affect RNA splicing

Answer 33

15%

Question 34

What is Beta(0)- thalassemia

Answer 34

• It’s a homozygous mutations that totally abolish normal splicing

Question 35

Beta(0)- thalassemia happens in which junction sequence

Answer 35

In the 5’-3’ intronic splice junction sequence of the hemoglobin gene

Question 36

What is beta(+) thalassemia

Answer 36

It’s a point mutation that changes the sequence in the polyadenylation signal site of the hemoglobin gene from AAUAAA to AACAAA