Gene Expression

Question 1

Central Dogma of Molecular Biology

Answer 1

All proteins originate from RNA

RNA is produced from DNA

Question 2

Keeping DNA Together

Answer 2

Hydrogen bonding

Nitrogenous base stacking

Question 3

Histones

Answer 3

Proteins
To be packaged, DNA is wound around them
Positively charged (to increase interaction with DNA)
Contain basic amino acids

Question 4

RNA

Answer 4

Produced by transcription
Smaller intermediate to convert genetic material (DNA) into diverse functional biomolecules (proteins)
Messenger RNA (mRNA) is copied from DNA and then travels to ribosomes (it all occurs in the cytoplasm in prokaryotes, while in eukaryotes, the transcription takes place in the nucleus, and mRNA then leaves through nuclear pores)

Question 5

Transcription Elongation

Answer 5

RNA Polymerase moves 3’ to 5’, catalyzing the polymerization of the daughter mRNA in a 5’ to 3’ direction
RNA Polymerase unwinds 10 to 20 nucleotides at a time
Multiple RNA Polymerase can work on the same gene at the same time

Question 6

Post-transcription

Answer 6

Clean up the mRNA (capping and PolyA tail addition and splicing)
Export the mRNA
Translation
Degradation

Question 7

Codon

Answer 7

3 nucleotides
Translates into one amino acid
AUG → Met (start of translation)
UAA, UAG and UGA → stop (end of translation)

Question 8

Transfer RNA (tRNA)

Answer 8

~64 of them exist, each one recognizing a specific codon
Binds to a codon with an anti-codon loop
tRNA are attached to specific amino acids beforehand (by tRNA synthetase)

Question 9

Translation

Answer 9

Coordinated by ribosomes
Has three steps: initiation (ribosome binds and looks for AUG), elongation (ribosome brings in tRNA) and termination (ribosome finds stop order and releases)

Question 10

Translation Initiation

Answer 10

Most complicated step in translation
mRNA must bind to ribosome
The ribosome must find the start of the mRNA to be translated
Initiation factors recruit the components

Question 11

Translation Elongation

Answer 11

Involves continuing to read the mRNA and adding amino acids to the growing polypeptide
Elongation factors are involved

Question 12

Translation Termination

Answer 12

There are three stop signals
There is no tRNA for these, instead it is a release factor
There is no amino acid on the release factor, so the polypeptide chain is released

Question 13

Mutations

Answer 13

Caused by RNA polymerase
Point mutations: silent (no effect on protein sequence), missense (amino acid substitution) and nonsense (stop codon substituted for an amino acid)
Frameshift mutations: when an insertion or deletion of nucleotides results in a shift in reading frame or insertion of stop codon