Biochemistry Practice Test 10

1. Trp repressor is a ____________

Homotrimer

Homodimer

Heterotrimer

Heterodimer

2. Which of the following is a hypertonic solution?

Red blood cells placed in fresh water

0.45% sodium chloride

Oceans

Freshwater habitats

3. The lac repressor has which of the following DNA-binding motif?

Homeodomain

Helix-turn-helix

Zinc finger

Leucine zipper

4. Which of the following inhibits initiation at higher concentrations?

Diphtheria toxin

Ricin

Streptomycin

Chloramphenicol

5. The binding of ligands to many GPCRs leads to ____________

Increase in concentration of first messengers

Decrease in concentration of first messengers

Decrease in concentration of second messengers

Increase in concentration of second messengers

6. In which of the following cases the first base of anticodon pairs with two codons?

When the first base of anticodon is A or G

When the first base of anticodon is A or C

When the first base of anticodon is inosine

When the first base of anticodon is G or U

7. Formation of the attenuator stem-and-loop structure depends on the events that occur during translation of ____________

Regulatory sequence 4

Regulatory sequence 3

Regulatory sequence 2

Regulatory sequence 1

8. Which type of splicing reaction requires a guanine nucleoside or nucleotide cofactor that is not used as a source of energy?

Group I

Spliceosomal

Group IV

Group II

9. Signal sequences are ____________

Short peptide sequences to transport a protein to the nucleus

Short peptide sequences attached to a protein that initiates its degradation by digestive enzymes

Glycoproteins that serve as an address for transporting newly synthesized protein to the correct location

Short peptide sequences that serve as an address for transporting newly synthesized proteins to the correct location

10. Which of the following about mRNA stability is not correct?

It is thought that poly-A tails stabilize eukaryotic mRNAs

Histone mRNAs have especially long poly-A tails and are stable

Prokaryotic mRNAs have a half-life of only a few minutes

Regulation of mRNA stability is a way of regulating gene expression