Gene Expression

Question 1

How does DNA become RNA?

Answer 1

Transcription

Question 2

How does RNA become a protein?

Answer 2

Translation

Question 3

Where does transcription happen?

Answer 3

In the nucleus

Question 4

Where does translation occur?

Answer 4

In the cytoplasm

MRNA leaves through the nuclear pore

Question 5

What starts/stops transcription + translation?

Answer 5

A signal such as Transcription/translation initiation/termination

Question 6

What is the standard template of requirements for making a polynucleotide or polypeptide?

Answer 6

Needs an enzyme
Needs activated substrates
Needs a template

3 stage process=initiation, elongation, termination

Question 7

Fill in the regular template for making DNA.

Answer 7

Enzyme=DNA polymerase
Substrates=dNTPs
Template=DNA
Process=initiation, elongation, termination

Question 8

Fill in the regular template for making RNA (transcription)

Answer 8

Enzyme=RNA polymerase
Substrates=NTPs
Template=DNA
Process= initiation, elongation and termination

Question 9

Fill in the template for making a polypeptide (Translation)

Answer 9

Enzyme=ribosome
Substrate=amino acids
Template=mRNA
Process=initiation, elongation and termination

Question 10

Describe the initiation in DNA replication

Answer 10

Initiation=recognition of origin of replication, initiate proteins and DNA polymerase

Question 11

Describe the elongation in DNA replication

Answer 11

5’ to 3’ chain growth

Question 12

Describe the termination step in DNA replication.

Answer 12

Termination=when the replication forks meet

Question 13

Describe the initiation step in transcription

Answer 13

Initiation=promotor region recognised, transcription infatuation factors, RNA polymerase

Question 14

Describe the elongation step in Transcription.

Answer 14

Elongation=5’ to 3’ chain growth

Question 15

Describe the termination step in transcription.

Answer 15

Sequence dependant (the way it terminates depends on the sequences coding)

Question 16

How can a gene also be referred to in transcription?

Answer 16

The transcription unit (the bit that forms the DNA)

Question 17

Give a difference between RNA and DNA polymerase.

Answer 17

RNA polymerase doesn’t need the same kickstart as DNA polymerase

Question 18

What does upstream refer to?

Answer 18

The DNA behind the RNA polymerase enzyme. Eg there may be other proteins binding upstream

Question 19

What does downstream refer to?

Answer 19

The DNA after the RNA polymerase protein, transcription occurs in this direction.

Question 20

What is a promotor sequence?

Answer 20

It interacts with RNA polymerase to begin transcription. Uses an activator to help it interact as it may be many bases away from the transcription site

Question 21

How is the DNA coding strand related to mRNA production?

Answer 21

It is not involved in the transcription process itself but contains the same sequence to mRNA (except for the T/U difference). This is because the coding strand is complementary to the strand used as the template (the DNA template strand) for mRNA

Question 22

How does pre-mRNA get to mature RNA?

Answer 22

Capping - at 5’ end to protect against degradation

Tailing/polyadenlyation - at the 3’ end, protect against degradation

Splicing-to remove introns, is sequence independent

Question 23

What is capping?

Answer 23

Happens at the 5’ end.
A 5’-5’ linkage is created with the end nucleotide and a mentholated Guanine.
It plays a role in protection against nucleotide degradation.

Question 24

What is Polyadenylation?

Answer 24

On the 3’ end a specific endonuclease is used to cleave the new mRNA from the RNA polymerase.
This cleaved mRNA then uses the enzyme to add a large number of Adenine nucleotides to the mRNA.

Question 25

What happens in splicing?

Answer 25

The non-coding Introns are removed from the pre-mRNA leaving only the coding Exons to make up the mRNA.

Question 26

What are Prokaryotic ribosomes used for?

Answer 26

Can be used to program antibiotic targeting as they are different to eukaryotic ribosomes. It gives the antibiotic something to target.

Question 27

What are 3 key types of RNA?

Answer 27

Ribosomal RNA= rRNA Messenger RNA= mRNA Transfer RNA= tRNA

Question 28

What type of RNA is most prominent in the cell?

Answer 28

Ribosomal RNA makes up 80% of a cells RNA at one time

Question 29

Why is Translation regarded as more complicated than Transcription?

Answer 29

From 4-letter nucleotides to 20 amino acids | Adaptor molecule is needed

Question 30

What features of the DNA sequence are important in sequencing?

Answer 30

Triplet Code Degenerate (multiple triplets produce same amino acids Non-overlapping Comma-less (no gaps between codons) 5’-3’ strand produces N to C polypeptide chain

Question 31

What adapter molecule is needed in translation?

Answer 31

-tRNA

Question 32

What is the initiation codon?

Answer 32

AUG

Question 33

Fill in the standard template for translation?

Answer 33

Enzyme=ribosome Substrate=amino acids Template=mRNA Process=initiation, elongation, termination

Question 34

What shape is tRNA?

Answer 34

A clover Has anticodon at bottom Is a single stranded molecule that forms double stranded sections

Question 35

What are stem loops in tRNA and why are they important?

Answer 35

They occur when hydrogen bonds are formed between anti-parallel , complimentary sequences. They are important as they allow the clover shape to form

Question 36

What does Amino-acyl tRNA refer to?

Answer 36

A tRNA molecule that has a specific aminoacyl group attached to it. It is specific to the anti codon on the molecule.

Question 37

What is a “wobble” region on tRNA?

Answer 37

The 5’ base of the codon and hence the 3’ base of the codon is the “wobble” position. Contains an I base on the anticodon . This can be complementary to any base T,A,C,G on ,RNA, and so a single tRNA can recognise more than one mRNA codon. This means different codons on mRNA can code for the same amino acid (as they have the same anticodon)

Question 38

How are amino acids activated?

Answer 38

ATP binds to a specific enzyme (aminoacyl-tRNA synthetase) and this binds to the specific amino acid. The ATP looses phosphate giving the amino acid the energy to bind to the tRNA. The enzyme helps the AA bind to the tRNA molecule with the matching anticodon (this is when the now AMP is released). The bond is created and the anticodon (now holding an AA) is released from the enzyme.

Question 39

What is the initiation step in Translation?

Answer 39

Initiation=AUG codon is recognised, special Methionyl tRNA activated , ribosome active

Question 40

What is the elongation process in Translation?

Answer 40

Elongation=N to C chain growth using aminoacyl tRNA’s

Question 41

What is the termination step in Translation?

Answer 41

Termination=STO codon reached

Question 42

What are the two exposed sites on the ribosome called and what are there roles?

Answer 42

P site and A site The P site has the first AA and then the second picks one up. This then moves from the A site and binds to the AA on the P site, starting a chain.