Molecular Basis of Gene Transcription

Question 1

The 3 types of RNA?

Answer 1

mRNA - copied from DNA to encode proteins
rRNA - structural and enzymatic component of ribosomes
tRNA - delivers amino acids to the ribosome

Question 2

Initiation in gene transcription?

Answer 2

1) short recognition sequence in the promotor region is aligned with RNA polymerase
2) Sigma factor binds to region, recruiting RNA polymerase to the transcription start site

Question 3

Elongation in gene transcription?

Answer 3

1) RNA polymerase unwinds DNA, reads the template and synthesises mRNA by adding complementary nucleotides
2) After a few nucleotides are added the sigma factor dissociates
3) nucleotides are added in the 5’ to 3’ direction (joined by phosphodiester bonds)

Question 4

Termination in gene transcription?

Answer 4

1) Controlled by GC rich stop sequences in DNA

2) mRNA transcript forms stem loop and reduces binding of mRNA to DNA so then the base pairings detach from the template

Question 5

Uses of RHO?

Answer 5

RHO has helicase activity and unwinds DNA-RNA duplex, separating RNA from DNA
When RNA polymerase stalls the rho catches up and releases RNA

Question 6

The 3 types of RNA polymerase and what they cleave?

Answer 6

RNA pol 1 - rRNA
RNA pol 2 - mRNA and snRNA
RNA pol 3 - 5srRNA and tRNA

Question 7

What is eukaryote capping?

Answer 7

When a 7-methylguanosine cap formed at 5’ end
added by a reaction with GTP
it protects the transcript from degradation

Question 8

What is polyadenylation?

Answer 8

When adenosine residues are added to the 3’ end of mRNA to export and protect the transcript from degradation

Question 9

What is splicing?

Answer 9

Splicing is when the complex of proteins remove the introns via the spliceosome