Intro To Molecular Biology 3

Question 1

Differences in structure between DNA and RNA:

Answer 1

DNA = double helix

RNA = single strand + may have secondary or tertiary structure (more complex)

Question 2

Function of DNA:

Answer 2

Information storage

Question 3

Functions of RNA:

Answer 3

Genetic message - mRNA

Adaptor - tRNA

Structural RNAs - Xist

Catalyst - rRNAs , spliceosome snRNAs

Guide RNAs - for RNA editing

Question 4

What’s involved in transcription?

Answer 4

DNA used as template

Complementary to one strand

RNA polymerase (5’ to 3’)

Not as accurate as DNA replication

Question 5

Difference between RNA polymerase and DNA polymerase:

Answer 5

RNA = polymerises 40 bases/second

DNA = 100 bases/second

RNA polymerase doesn’t require primer

Question 6

What’s the coding strand in transcription?

Answer 6

Non-template strand

Question 7

Characteristics of coding strand:

Answer 7

Sequence equal to RNA

Not all genes on chromosome are in same orientation

Question 8

What’s important to know about copies of RNA?

Answer 8

Many copies are made simultaneously

Question 9

What are promoters?

Answer 9

Region of DNA

Found before transcription site, signals its beginning

Question 10

What are terminators?

Answer 10

Region of DNA

Marks end of transcription

Question 11

What are the 3 different types of RNA polymerase?

Answer 11

RNA pol I

RNA pol II

RNA pol III

Question 12

What RNA does RNA pol I generate?

Answer 12

rRNA

Question 13

What RNA does RNA pol II generate?

Answer 13

Protein coding RNA

Question 14

What RNA does RNA pol III generate?

Answer 14

tRNA

Question 15

What’s the promoter for RNA pol II?

Answer 15

TATA box

Question 16

What does the TATA box do?

Answer 16

Facilitates binding of RNA polymerase and transcription factors (e.g. TBP)

Located 25 bases upstream of starter code

Question 17

What does TBP mean?

Answer 17

TATA binding factor

Question 18

What doers TBP do?

Answer 18

Distorts shape of DNA once bound - allows binding of RNA pol II

Question 19

What does TBP do to the shape of DNA?

Answer 19

Creates ink in DNA and binds minor groove

Facilitates strand opening to allow transcription to start

Question 20

What’s the core promoter?

Answer 20

Basal transcription

Question 21

What does the regulating gene do?

Answer 21

Transcription is tightly controlled - e.g. insulin

Question 22

What does the housekeeping gene do?

Answer 22

Transcription always on - e.g. actin

Question 23

How does RNA polymerase bind to DNA?

Answer 23

RNA polymerase binds to factor-promoter complex

Trans-acting factors bind to cis-acting promoter

RNA cannot bind directly to promoter

Question 24

What are enhancers?

Answer 24

Short DNA sequences

50-1500 base pairs

Question 25

Where are enhancers located?

Answer 25

Not always located close to transcription start site as they can work from a distance

Question 26

What do enhancers do?

Answer 26

Bind to transcription factors to increase likelihood of specific section of DNA being transcripted Stabilise transcription machinery assembly by protein-protein interactions

Question 27

What are enhancers opposed by?

Answer 27

Silencers

Question 28

What are the two domains of transcription factors?

Answer 28

DNA binding domain Activation domain

Question 29

What ways can transcription be controlled?

Answer 29

Protein only synthesised when transcription happens Protein inactivated by phosphorylation, dephosphorylation and ligand binding Protein inhibited and rendered inactive by inhibitor Protein has inactive binding partner switched with active binding partner

Question 30

Why must mRNA be processed?

Answer 30

Protection from exonucleases Aid export from nucleus Identified as mRNA

Question 31

What are exonucleases?

Answer 31

Enzymes which cleave nucleotides

Question 32

What are introns?

Answer 32

Non-coding segment of DNA/RNA

Question 33

What are exons?

Answer 33

Coding segment of DNA/RNA after introns are spliced

Question 34

What was the sequence of information in genes and proteins known to be?

Answer 34

Co-linear

Question 35

What was the sequence of information in genes discovered to be?

Answer 35

Interrupted - not contiguous

Question 36

What does splicing take place through?

Answer 36

2 esterification reactions

Question 37

Importance of post-transcriptional modifications:

Answer 37

Many different proteins made from same DNA