12.2

Question 1

eukaryotic transcription

Answer 1

-occurs in the nucleus
-3 different RNA polymerases
(RNA polymerase 2 transcribes mRNA)
-promoter position and sequence differs from prokarytoes
-a series of transcription factors recruit and activate RNA pol 2
-termination sites are not well defined
-primary transcripts are process to produce mature mRNA

Question 2

processing of eukaryotic mRNA

Answer 2

Primary transcript is modified to mature mRNA by:
-addition of 5’ cap
-addition of 3’ poly-A tail
-removal of non-coding region (introns) by spliceosome

Question 3

5’ cap

Answer 3

protects mRNA from degradation; helps alignn mRNA for translation

Question 4

3’ poly-A-tail

Answer 4

protects mRNA from degradation

Question 5

splicing of eukaryotic pre-mRNA

Answer 5

many eukaryotic genes contain exons interspersed with introns:
-exons
-introns
-snRNPS (small-nuclear ribonucleoprotein particles)
-output of processing

Question 6

exons

Answer 6

coding regions that specify amino acids

Question 7

introns

Answer 7

non coding regions that don’t need to be translated

Question 8

snRNPS (small-nuclear ribonculeoprotein particles)

Answer 8

combine with other proteins to form the spliceosome-removes introns and splices together exons

Question 9

output of processing

Answer 9

mature RNA

Question 10

alternative splicing

Answer 10

-single primary transcript may be spliced into different mRNAs by the inclusion of different sets of exons
-can produce different proteins from single gene
*20,000 genes in human genome can encode>80,000 different mRNAs