Transcription

Question 1

Transcription

Answer 1

DNA is doubled-stranded and is found inside the nucleus

DNA is copied into single-stranded RNA which is transported into the cytoplasm

Question 2

Initiation - Transcription

Answer 2

The enzyme RNA polymerase binds to DNA

The binding occurs at a promoter

The promoter usually has a characteristic base pair pattern (TATA box)

called this because of the hydrogen bonds (2 hydrogen bonds), less energy required for rna polymerase! why its used!!!

Question 3

Elongation - transcription

Answer 3

RNA polymerase builds the single-stranded RNA molecule from the template (antisense) DNA strand

RNA polymerase elongates from 5’ to 3’

The DNA strands reform a helix as RNA polymerase passes through

send message from 5’ to 3’ bc thats how ribosome reads it

5’ to 3’ will be the sense strand
3’ to 5’ will be antisense

Question 4

Elongation Transcription Notes

Answer 4

The copied RNA strand is called the primary transcript

RNA polymerase does not require a primer to start

The promoter itself is not copied
- it is used to start transcription, but it is not part of the product

There may be many RNA polymerases copying the same gene at once

Question 5

Termination - Transcription

Answer 5

RNA polymerase recognizes the end of the gene when it comes across a terminator sequence

Transcription stops and RNA polymerase is free to bind another promoter and transcribe another gene

Question 6

Post Transcriptional Modifications

Answer 6

• 5’ cap
  poly-A tail
  Removal of introns

Question 7

5’ cap

Answer 7

start of primary transcript
- 7 G’s
protection from degregation from nucleus to cytoplasm

Question 8

Poly-A Tail

Answer 8

Added to the 3’ end of the primary transcript
- Sequence of 50-250 A’s
- protection from degregation when RNA leaves nucleus and enters the cytoplasm

Question 9

Exons and Introns

Answer 9

Recall that the DNA of eukaryotic organisms is a mixture of
coding regions called exons
noncoding regions called introns

Introns are removed by spliceosomes

Question 10

How are introns removed?

Answer 10

1. Pre-mRNA + protien SnRNPS bind to the intron to create loop
2. extrons in the ends bond and splicosome cleaves intron (by folding it back in itself)
3. the intron is degraded, released SnRNPS are reused, and mRNA is created!