7.2 Transcription

Question 1

3 main steps

Answer 1

initiation, elongation, termination

Question 2

initiation

Answer 2

promoter sequence of DNA
initiates RNA replication

Question 3

elongation

Answer 3

RNA molecule is made by
adding nucleotides

Question 4

termination

Answer 4

RNA molecule is released once it reaches a termination sequence

Question 5

describe what happens in initiation

Answer 5

Enzyme RNA Polymerase binds to DNA at a Promoter (a DNA sequence that lies
just before a gene)

A key part of the Promoter is the TATA box which is a sequence of DNA that
contains Thymine and Adenine (These
nucleotides make the DNA easier to unwind since they contain less hydrogen bonds)

Question 6

In elongation, RNA is made in what direction using which strand?

Answer 6

RNA is made in the 5’🡪 3’ Direction (follows
DNA from 3’🡪 5’) using template strand

Question 7

In elongation what is the strand called that isn’t used?

Answer 7

coding strand

Question 8

True or false:

In elongation, Newly synthesised mRNA is the same as the coding strand (with exception of T/U)

Answer 8

True

Question 9

what happens in elongation

Answer 9

RNA Polymerase unwinds DNA and adds nucleotides to build an RNA strand

Once one RNA polymerase molecule has passed the beginning of a gene another can attach and make another copy of the same
gene

This allows multiple copies of a gene to be made simultaneously

Question 10

What happens in termination

Answer 10

RNA transcription stops when RNA polymerase reaches a termination sequence

Termination Sequence –
a section of bases at the
end of a gene that stops
RNA transcription

Question 11

Poly A Tail

Answer 11

a chain of adenine added to the 3’ end of the RNA

formed via poly-A polymerase

Protects the RNA from enzymes in the cytosol

Question 12

5’ Cap

Answer 12

seven guanine bases attached to the
beginning of the RNA strand

-protects from enzyme digestion during translation

Acts as an attachment site for ribosomes to
initiate translation

Question 13

Post-transcriptional modifications

Answer 13

Parts of mRNA in
Eukaryotes (introns) are
not transcribed—do not
code for proteins

If transcribed, protein
would fold improperly

Prokaryotes have no
introns (they have no
true nucleus…
transcription and
translation occur
simultaneously in
cytosol)

Question 14

intron

Answer 14

-a non-coding sequence of DNA or RNA

Introns need to be removed from RNA–spliceosomes

Introns stay in the nucleus

Question 15

exon

Answer 15

-a sequence of DNA/RNA that has coding regions of a gene

Exons in RNA need to be connected by removing
introns

Exons exit the nucleus

Question 16

small ribonucloproteins (snRNP’s)

Answer 16

–proteins that bind to introns and signals them for
removal

snRNP’s bind to introns and form an intron loop

Question 17

spliceosome

Answer 17

-enzyme that removes introns from RNA

Spliceosomes cut off intron loop and attaches the RNA together

Question 18

alternative splicing

Answer 18

–a process that produces different mRNA’s from pre mRNA

Allows for more than one polypeptide to be made from a single gene