Transcription

Question 1

RNA: general features

Answer 1

• ribonucleic acid
• Uracil replaces Thymine
• single stranded (folds into itself)
• less stable than DNA

Question 2

central dogma:

Answer 2

• flow of information:
• transcription
• translation
• protein

Question 3

hypotheses on one gene one ?

Answer 3

• 1 gene 1 enzyme
• 1 gene 1 protein
• 1 gene 1 polypeptide
• not correct (alternative splicing)

Question 4

transcription:

Answer 4

• synthesis of RNA using DNA
• similar to DNA replication
• uses DNA as template for complementary RNA strand

Question 5

types of RNA and job:

Answer 5

mRNA:

• messenger RNA
• carries message from DNA to protein

rRNA:

• ribosomal RNA
• structural RNA which forms ribosome

tRNA:

• transfer RNA
• structural RNA involved in synthesis of amino acid chains

Question 6

where does transcription occur in eukaryote and prokaryote:

Answer 6

prokaryote:
- no nuclei

eukaryote:

• transcription and RNA processing inside nucleus
• translation in cytoplasm

Question 7

template strand:

Answer 7

• 1 of 2 strand of DNA

- 3’ to 5’

Question 8

how does RNA synthesise to DNA template strand:

Answer 8

• antiparallel direction
• T replaced with U
• synthesised 5’ to 3’ direction

Question 9

coding strand:

Answer 9

identical to RNA strand (but has T)

- non-template strand (5’ to 3’)

Question 10

transcription process: overview

Answer 10

• RNA polymerase separate DNA double helix and adds RNA nucleotides
• RNA pol adds in 5’ to 3’ direction
• don’t need primer
• only 1 RNA pol in bacteria vs at least 3 in eukaryotes

Question 11

promoter:

Answer 11

where RNA pol attaches and starts transcription

Question 12

terminator:

Answer 12

in bacteria where transcription stops

Question 13

upstream and downstream?

Answer 13

• promotor end is upstream

- terminator end is downstream

Question 14

list stages of transcription:

Answer 14

• initiation
• elongation
• termination

Question 15

initiation: prokaryote

Answer 15

RNA pol binds to promoter region

Question 16

initiation: eukaryote

Answer 16

transcription factors mediate binding of RNA pol II

- TATA box needed to initate transcription

Question 17

elongation: both

Answer 17

• RNA pol untwists double helix 10-20 nucleotides at a time
• adds to 3’ end
• in convoy, multiple RNA pol can transcribe same gene to make proteins quickly

adds 40 nucleotides/ sec in eukaryotes

Question 18

termination: both

Answer 18

bacteria:
- transcribed terminator signal causes RNA pol to detach

eukaryotes:

• polydenylation signal AAUAAA signals proteins to bind RNA molecule, cut it, release RNA pol from RNA transcript
• proteins cleave off RNA pol II

Question 19

RNA processing contd:

Answer 19

• pre-mRNA is produced in eukaryotes
• occurs in nucleus
• 5’ cap added and (50-250 As) are added to 3’ end to form poly A tail

Question 20

purpose of poly A tail and 5’ cap

Answer 20

• help export mRNA out of nucleus into cytoplasm
• protect mRNA from degradation
• help ribosomes attach to 5’ end of mRNA

Question 21

mRNA splicing:

Answer 21

• non coding regions are removed
• exons spliced together
• spliceosome cuts out introns
• mature RNA moves into cytoplasm

Question 22

universal information flow:

Answer 22

almost universal flow of information from bacteria to eukaryotes

• supports common ancestry
• biotech: eg. insulin from humans into bacteria to mass produce

Question 23

alternative mRNA splicing

Answer 23

when introns are cut out and different sections are spliced together to form proteins