Control of gene expression in eukaryotes part 3

Question 1

What five properties define active chromatin

Answer 1

i) decondensed structure, absence of histone H1
ii) reduced content in methylated cytosine (5meC)
iii) high proportion of acetylated histones.
iv) Presence of regulatory proteins (mainly activators) bound to their target sites on
the DNA.
v) Increased sensitivity to nucleases

Question 2

What the four different types of alternative splicing

Answer 2

1. optional exon
2. optional intron
3. Mutually exclusive exons
4. Internal splice site (in an intron)

Question 3

Define constitutive splicing

Answer 3

Two different splice variants occur from the same strand

Question 4

Define regulated splicing

Answer 4

Proteins bind that either facilitate or prevent splicing

Question 5

What is the main factor that causes either a long or short transcript to be generated in the B lymphocyte example?

Answer 5

Conecentration of CstF: if lots of it, short transcript is made

Question 6

Define nonsense mRNA degradtion

Answer 6

Mechanism that allows the cell to degrade mRNA with a premature stop codon. Makes use of EJCs and UpF proteins to mediate degradation

Question 7

Define upF proteins

Answer 7

attracted by ribosome and EJC in context of premature stop codon.

Question 8

Define ADAR

Answer 8

• Adenosine Deaminase Acting on RNA
• often works near splice sites, changing adenosine to inosine.
• inosine has similar properties to guanine

Question 9

What are the four types of polarizing distribution?

Answer 9

Posterior, anterior, terminal, or dorsoventral

Question 10

What role does the 3” UTR play?

Answer 10

This is where transport proteins bind the mRNA

Question 11

What exonuclease shortens Poly-A tails?

Answer 11

Deadenylase

Question 12

What role does the 3’UTR play in degradation

Answer 12

It has target sequences of endonucleases