Exam questions?

Question 1

What is the Kozak consensus sequence?

Answer 1

In eukaryotic mRNA. The Kozak consensus sequence plays a major role in the initiation of the translation process

Question 2

What are two ways to ensure proper amino acid is added to peptide?

Answer 2

1. tRNA aminoacyl syntathase checks that the tRNA and the aa are correctly matched before adding the protein to the 3’CCA of the tRNA. Once the aa is bound, it is moved from the catabolic site to the proofreading site, where correct pairing of aa and tRNA is confirmed.
2. Codon-anticodon matching is verified by a conformational change in 26rRNA upon binding to groove between first two base-pairs from the codon-anticodon pair. If conformational change doe snot occur, aminoacyl-tRNA dissociates.

Question 3

Mention two drugs that only affect bacterial translation?

Answer 3

Streptomyocin: binds 30S ribosome
Cloramphenicol: binds 50S inhibiting transpeptidation

Question 4

What type of bonding is required in phosphorylation?

Answer 4

covalent bonding

Question 5

How do you distinguish between marasmus and kwashiorkor?

Answer 5

• Marasmus patients have an extremely emaciated look because of wasting of muscle and fat stores. Body weight less than 60% the normal, energy deficiency.
• Kwashiorkor patients also look very thin, but they present abdominal edema. Protein-energy malnutrition is characterized by edema, irritability, anorexia, ulcerating dermatoses, & enlarged liver.

Question 6

Phosphorylation occurs most in which aa?

Answer 6

Ser > Thr > Tyr

Question 7

What occurs in ricin poisoning?

Answer 7

If ricin (from castor beans) is injected, inhaled, or ingested, it can stop protein synthesis. It binds to the 60S ribosomal subunit inhibiting attachment of eEF2. This stops peptide chain elongation.

Question 8

What are heterotrophic and homotrophic effectors?

Answer 8

• Homotropic: substrate, as well as a regulatory of the enzyme’s activity. Tpically an activator of the enzyme. For example, O2 is a homotropic allosteric modulator of hemoglobin.
• Heterotropic: regulatory molecule that is not also the enzyme’s substrate. It may be either an activator or an inhibitor of the enzyme. For example, H+, CO2, and 2,3-BPG are heterotropic allosteric modulators of hemoglobin.

Question 9

How to distinguish between nucleic acids?

Answer 9

A & G: two rings (guanine has a carbonyl)

C, T, U: 1 ring (thymine has a methyl and 2 carbonyls, uracil has two carbonyls, cytosine has one carbonyls and 1 NH2)

Question 10

How many high energy bonds are required for peptide bond formation?

Answer 10

Two, indirectly from GTP associated with GF-tu

Question 11

What are some common genome sizes?

Answer 11

SV40 virus: 5 kb
Lambda: 40kb
Mycobacterium: 580 kb
Influenza: 1.8Mb
E. Coli 4.6 Mb
Yeast: 12Mb
Drosophila: 180 Mbp
C. elegans: 97 Mb
Human 3 G

Question 12

Northern and southern blots are for?

Answer 12

Northern: RNA
Southern: DNA

Question 13

Some characteristics specific to eukaryotes?

Answer 13

• Multiple RNA Pols
• General TFs and holoenzyme
• TATA box
• RNA Pol II

Question 14

What are the steps in mrNA processing?

Answer 14

1. cap
2. splice
3. 3’ cleavage
4. polyA
5. nuclear expor
6. translation
7. deadenylation