Genes and Chromosomes (Part 2)

Question 1

What are the functions of the 7-Me G - 5’ mRNA Cap?

Answer 1

1) •Regulates export of mRNA out of the nucleus:
2) •Required for the efficient translation of the mRNA into protein
3) •CAP and the CAP binding proteins slows 5’ degradation of the mRNA.

Question 2

Mature mRNA is exported in ____ that contain a _____ at the ___ along the rest of the sequence

Answer 2

complexes
Cap Binding Complex (CBC)
5’ end & RNA binding proteins

Question 3

The cap binding complex on the mRNA facilitates recognition by what?

Answer 3

Translation initiation machinery

Question 4

How does CAP and the CAP binding proteins slows 5’ degradation of the mRNA?

Answer 4

By blockage of de-capping enzymes to the cap

-this increases the t1⁄2 of the mRNA

Question 5

What are the Functions of 3’ mRNA Polyadenylation?

Answer 5

• Poly-A tail Increases the t1⁄2 of the mRNA by protecting it from enzymatic degradation in the cytoplasm
• PABP interacts with stuff at the 7-Me-G CAP

Question 6

The 5’ splice donor sequence always possesses a ___ sequence & the 3’ splice acceptor always an ___ sequence

Answer 6

• GU

- AG

Question 7

Lariat structure forms as the __ splice donor links to the invariant__ within the intron

Answer 7

• 5’

- A

Question 8

What allows for a corresponding number of different proteins to be produced from the same gene?

Answer 8

Alternative variations in splicing

Question 9

Editing of apolipoprotein-B mRNA:
In human liver, unedited mRNA is translated to yield a 4536-amino-acid protein called ____. In human intestine, however, the mRNA is edited by a base modification that changes a specific ___. This modification changes the codon for ____ to a ___, resulting in synthesis of _____.

Answer 9

• Apo-B100
• C to a U
• glutamine (CAA)
• termination codon (UAA)
• a shorter protein (Apo-B48, consisting of only 2152 amino acids).

Question 10

What type of RNA does RNA Polymerase 1 transcribe in eukaryotes?

Answer 10

1) RNA pol I: rRNA genes (nucleoli)
- Most abundant RNA in cells
- Protein synthesis machinery

Question 11

What type of RNA does RNA Polymerase II transcribe in eukaryotes?

Answer 11

mRNA from all protein-coding genes & some snRNAs.

Question 12

What is inhibited by α-amanatin (poison deathcap mushroom)?

Answer 12

RNA Polymerase II

Question 13

What type of RNA is transcribed by RNA Polymerase III?

Answer 13

RNA pol III: tRNA genes & some snRNAs

• 2nd most abundant RNA species in cells
• tRNA is the adaptor molecule between NA and peptide

Question 14

What are enhancers and what is its role?

Answer 14

Cis acting DNA sequences (on the same chromosome) that enhance the rate of transcription by RNA Polymerase II.

Question 15

What type of transcription factors do enhancers bind to?

Answer 15

Activators

Question 16

Enhancers contain DNA sequences called ‘___.’ These Bind to transcription factors called _____.

Answer 16

• response elements

- activators