Molecular Biology

Question 1

How many codons in normal eukaryote cells?

Answer 1

64 in total.
61 code for amino acids.
3 code for stop codons.

Question 2

What does DNAa do?

Answer 2

Recognises the Ori region and gives a conformational change in the DNA to start unwinding.

Question 3

What does DNAb do?

Answer 3

DNAb is helicase. It’s a six unit ring structure that unzips the DNA, knocking off anything in the way.

Question 4

What does DNAc do?

Answer 4

DNAc breaks open the hexomer of helicase and mounts it on the DNA strand, before repairing the hexomer.

Question 5

In Transcription what is promoter and what is it recognised by?

Answer 5

The promoter is the -35 & -10 regions and they are recognised by the Sigma factor.

Question 6

In DNA Replication what is the promoter and what is it recognised by?

Answer 6

The Ori region is the promotor and it is recognised by DNAa.

Question 7

What terminates Replication?

Answer 7

Topoisomerase or telomerase.

Question 8

What terminates Transcription?

Answer 8

The formation of a hair-pin loop or Rho protein.

Question 9

A Millimetre is how large?

Answer 9

10^-3 metres

Question 10

A nanometre is how large?

Answer 10

10^-6 metres

Question 11

A micrometer is how large?

Answer 11

10^-9 metres

Question 12

What is AB1157?

Answer 12

The wild type strand of E.coli.

Question 13

In a Molecular Biology lab what three things must you check before you start an exercise?

Answer 13

That you have been provided the correct equipment foe the experiment.

Find out where and at what temperature the experimental organisms are kept.

Know the correct genetic markers for the experimental organisms.

Question 14

What are the three stop codons?

Answer 14

UAA, UAG & UGA

Question 15

What codon is the “start” of most genes?

Answer 15

The codon is AUG which codes for Metformin (Met)

Question 16

What direction do RNA and DNA polymerase build in?

Answer 16

They build in the 5’—>3’ direction, which means they move from the 3’ end to the 5’ end of the molecule.

Question 17

What are we refering to when we talk about the “Fidelity” of a DNA polymerase.

Answer 17

Fidelity is the polymerases ability to accurately replicate a template.

Question 18

Name three spontaneous mutations.

Answer 18

Tautomerism: The amino acid swaps to a imino acid which is a constitutional isomer.

Deamination: The NH2 amino group can be hydrolysed and lost, you then have a uracil.

Depurination: The bond holding the base to the sugar gets cleaved.

Question 19

What does Dam Methylase do?

Answer 19

Adds a methyl group to thymine groups to mark older strands to help MutS when it does DNA mismatch repair.

Question 20

What is a “Generalised Transducer”

Answer 20

It is a lytic phage that breaks down the nuclear envelop and packages some bacterial DNA by chance, this becomes a generalised transducing particle.

Question 21

What is a “Transductant”

Answer 21

A cell that has become genetically recombinant through horizontal gene transfer involving transducing particles.

Question 22

What is a “Generalised Transducer”

Answer 22

It is a lytic phage that breaks down the nuclear envelop and packages some bacterial DNA by chance, this becomes a generalised transducing particle.

Question 23

What is a “Transductant”

Answer 23

A cell that has become genetically recombinant through horizontal gene transfer involving transducing particles.

Question 24

What is the difference between Polycistronic mRNA and Monocistronic mRNA?

Answer 24

Polycistronic mRNA has multiple ORF’s on a single strand and is more commonly found in prokaryotes.

Monocistronic mRNA has only one ORF per strand and is more commonly found in eukaryotes.

Question 25

What is the Acceptor stem part of tRNA

Answer 25

This is the extreme 3’ end of the tRNA that has the CCA tag that is the site of amino acid attachment.

Question 26

What is the Psudo-U loop of tRNA?

Answer 26

The Psudo-U loop is named for the highly conserved alternative nucleotide Psudouracil that is present there.

Question 27

What is the Anti-codon loop of tRNA?

Answer 27

The anticodon loop is where the anticodon is located, this is where the tRNA interfaces with the mRNA.

The anticodon is always bracketed by a 3’-purine and a 5’-uracil.

Question 28

What is the D loop of tRNA?

Answer 28

The D loop is named for the presence of the highly conserved alternative nucleotides Dihydrouridines.

Question 29

What does Beta-Galactosidase do?

Answer 29

Breaks down lactose into galactose and glucose via allolactose.

Question 30

What is basal level expression?

Answer 30

Basal level of expression is the level of expression present with no positive or negative infulence. This is dictated by the affinity the RNA polymerase has for the promotor sequence.

Question 31

What are the genes Lac-Z, Lac-Y and Lac-I responsible for?

Answer 31

• Lac-Z* : Codes for beta-galactosidase.
• Lac-Y* : Codes for the permease.
• Lac-I* : Codes for the repressor/ Inhibitor

Question 32

What is “Induction”?

Answer 32

Induction is when a gene is expressed because of the switching off of the repressor.

Lac-I binds to Lac-O to repress but can be induced by allolactose acting as an inducer to release Lac-O and allow transcription.

Question 33

Lac-Z has three operons associated with it O1,O2 and O3. How does this add a level of repression?

Answer 33

The Lac repressor will bind O1 and one of the other two regions simultaneously, this twists the DNA adding terrane repression.

Question 34

What is Lac-O positively regulated by?

Answer 34

The CAP (sometimes CRP) which is : Catabolite Activator Protein.

CAP requires 2 cAMP to bind to Lac-O this is regulated as cAMP levels drop off as glucose levels increase.

Question 35

What is F-factor in E.coli?

Answer 35

A viral plasmid with NO extracellular lifecycle, so they are brilliant genetic tools and used in complementation tests.