Transcription and mRNA processing

Question 1

RNA polymerase

Answer 1

catalyzes RNA synthesis, pries DNA strands apart and joins together RNA nucleotides

Question 2

Anatomy of Gene: bacteria

Answer 2

Upstream sequence: transcription initiation sequence and promoter
Downstream sequence: transcription termination site and terminator

Question 3

Three stages of transcription

Answer 3

Initiation, elongation, termination

Question 4

Initiation

Answer 4

After RNA polymerase binds to promoter, the polymerase unwinds the DNA strands and begins RNA synthesist start point of template strand

Question 5

Elongation

Answer 5

the polymerase moves downstream, unwinding the DNA and elongating the RNA transcript in a 5’ to 3’ direction; after transcription, DNA strands rejoin and form double helix

Question 6

Termination

Answer 6

RNA transcript is released and polymerase detaches from DNA

Question 7

Promoter

Answer 7

specific nucleotide sequence in DNA of a gene that binds RNA polymerase; positioned to start transcribing RNA at appropriate place

Question 8

Terminator

Answer 8

In bacteria; sequence of nucleotides in DNA that marks ends of genes and signals RNA polymerase to release newly synthesized RNA and detach from DNA

Question 9

Transcription unit

Answer 9

Region of DNA that is transcribed into RNA molecule

Question 10

Anatomy of a Gene: Eukaryotes

Answer 10

Upstream: Transcription initiation site and promoter
5’ UTR
Downstream: 3’ UTR; AAUAAA (polyadenylation signal) and transcription termination site

Question 11

RNA processing (eukaryotic)

Answer 11

Modification of RNA primary transcripts including splicing of introns, joining axons, and alteration of 5’ and/or 3’ ends

Question 12

Alteration of mRNA ends

Answer 12

5’ end: modified 5’ cap
3’ end: poly-A tail

Question 13

Why are mRNA ends changed?

Answer 13

to facilitate mRNA export to cytoplasm, protect mRNA from hydrolytic enzymes, help ribosomes attach to 5’ end

Question 14

5’ cap

Answer 14

modified guanine nucleotide attaches to 5’ end

Question 15

Poly-A tail

Answer 15

50-250 adenine nucleotides attached to 3’ end

Question 16

RNA splicing

Answer 16

removal of portions of the primary transcript (introns) that will not be included in mRNA; joining together of remaining portions (Exons)

Question 17

Introns

Answer 17

noncoding, intervening sequence within a primary transcript that is removed during RNA processing

Question 18

Exons

Answer 18

sequence within primary transcript that remains in RNA after processing

Question 19

Spliceosome

Answer 19

large complex made of protein and RNA molecules that splices RNA by interacting with ends of RNA introns; releases intron and joins together two exons

Question 20

Ribozymes

Answer 20

Catalytic RNA molecules that function as enzymes; example is intron catalyzing its own removal

Question 21

Alternative RNA splicing

Answer 21

eukaryotic gene regulation at RNA processing level; different mRNA molecules are produced from same primary transcript, depending on introns and exons