DNA, RNA and Genes

Question 1

Purines

Answer 1

Adenine (6-Amino-Purine) and Guanine

Question 2

Pyrimidines

Answer 2

Thymine, Uracil, Cytosine

Question 3

Modification of Uracil to make Thymine

Answer 3

5-Methyl Uracil

Question 4

What charge is prominent in DNA

Answer 4

Negative charge

Question 5

Differences on DNA & RNA (Carbon 2)

Answer 5

Protons on DNA, Hydroxyl on RNA

Question 6

Phosphodiester bond Direction

Answer 6

5’-3’

This is also convention when drawing DNA (left to right)

Question 7

How is the genome of hot spring insects different to humans

Answer 7

It is GC rich as those triple H bonds are more stable than the double H bonds of AT

Question 8

What is the reason for the helical twist of DNA?

Answer 8

Their hydrophobic nature causes interactions that make bases closer to one another to avoid water, also causing a spiral

Question 9

What happens when chemicals insert into stacked bases?

Answer 9

DNA polymerase is confused so an insertion mutation occurs where a base is added when there originally was nothing

Question 10

DNA Gyrase

Answer 10

Enzyme that stops the formation of super coils during DNA unwinding

Question 11

Okazaki Fragments

Answer 11

Segments of partially synthesised DNA formed on the lagging strand

Question 12

DNA Ligase

Answer 12

Enzyme that seals the nicks between okazaki fragments

Question 13

Why is DNA gyrase targeted for drug interventions

Answer 13

Eukaryotic DNA replication does not need DNA gyrase

Question 14

Why are Topoisomerase Enzymes targeted in Chemotherapy

Answer 14

Eukaryotic DNA replication requires topoisomerase enzymes

Question 15

hnRNA

Answer 15

Precursor to mRNA before post transcriptional modifications (includes introns)

Question 16

5’ Cap

Answer 16

Post-transcriptional addition added to mRNA that protects the transcript from being broken down and helps the ribosome attach to the mRNA and start reading it to make a protein

Question 17

What does 5’ cap always have and what is that thing’s role

Answer 17

Methyl guanine; important for recognition by ribosomes

Question 18

How is the 5’ Cap Added

Answer 18

5’-5’ Triphosphate linkage

Question 19

Explain how UTRs work with an example

Answer 19

Normally ferritin is a protein that stores iron. It is regulated by a protein that binds to a loop (Untranslated region/UTR) on ferritin mRNA which prevents rRNA from binding to it and translating.

When there is iron, Fe binds to the regulator and unbinds it from the mRNA to allow the formation of the iron storage protein ferritin

Question 20

What does a mutation to a UTR do?

Answer 20

Preventing the binding of a regulatory protein and thus the under-translation of a specific sequence

Question 21

How do ribosomes know which AUG is the right start codon?

Answer 21

In eukaryotes there is a “kozak consensus” sequences which tells ribosomes which is the right AUG to begin at and defines the reading frame

Question 22

Kozak Sequence

Answer 22

RccRccAUGG

This sequence defines how favourable the mRNA is to have protein made out of it, with certain sequences causing more protein to be synthesised from an mRNA molecule

The -3 R and +4 G are critical in determining favourability

• *DONT MEMORISE SEQUENCE
• *R MEANS PURINE
• *CHECK WIKIPEDIA IF CONFUSED

Question 23

Reading frame

Answer 23

AUG Defines the correct reading frame

Question 24

3’ Tail

Answer 24

Poly(A) tail

Post transcriptional addition onto mRNA that aids in efficient nuceleocytoplasmic transport, regulates mRNA stability and translation

Question 25

What consensus sequence is required on mRNA for a poly(A) tail

Answer 25

AAUAAA

Question 26

What is the +1 and -1 positions on an mRNA

Answer 26

+1 is always the A of AUG (Start codon)
-1 is the base right before that

**There is no 0 position