Ch. 14 RNA Processing

Question 1

ribonucleotides

Answer 1

NTPs

Question 2

deoxyribonucleotides

Answer 2

dNTPs

Question 3

ribosomes

Answer 3

rRNAs

Question 4

promoter

Answer 4

• initial binding site of the RNA polymerase

- specifies which polymerase is used for the different classes of genes to be transcribed

Question 5

transcription initiation

Answer 5

1. TF2D and TBP binds with TATA box and partially unwinds DNA
2. TF2s bind
3. Polymerase is positioned over start site
4. transcription bubble formed
5. Polymerase starts transcribing

Question 6

pre mRNA. what are the components?

Answer 6

pre messenger RNA

5’ untranslated region (UTR) needed for ribosome binding
receives 5’ methyl cap

3’ untranslated region (UTR) needed for mRNA stability and translation
AAAA tail

protein coding region

Question 7

how do we process pre-mRNA?

Answer 7

1. add 5’ methyl cap (says “don’t degrade me”)
   - required to initiate translation
   - adds stability
   - influences intron splicing
   - added during transcription
2. add Poly (A) tail
   - “polyadenylation”
   - adds stability
   - facilitates attachment of ribosome to mRNA
   - helps export mRNA out of nucleus
3. intron splicing

Question 8

how do we add 5’ methyl cap?

Answer 8

1. remove phosphate from 5’ nucleotide
2. add G (guanine)
3. methylation of added G
4. methylation of a few of the nucleotides at the 5’ end on their 2 - OH
   * only place where we see 5’ to 5’ bond*

Question 9

how do we add Poly (A) tail?

Answer 9

50 to 250 A’s added to the end of the transcript

-not coded in the DNA (post transcriptional modification)

Question 10

introns

Answer 10

non-coding regions of mRNA

not all of the mRNA codes into proteins!

Question 11

spliceosome

Answer 11

carries out mRNA splicing

• composed of 5 RNA molecules (snRNAs, small nuclear RNAs) and almost 300 proteins
• U1, U2, U4, U5, U6 - different types of snRNAs that play a role in splicing

Question 12

alternative splicing

Answer 12

the same gene produces identical pre-mRNAs but are alternatively processed

• important source of protein diversity!
• 60% of human genes are alternatively spliced