Question

Explain why its the answer

1. Which amino acid sequence would most likely be for the transmembrane domain of a plasma membrane protein

a) SKDTRENHQY

b) KRHGPRKHRK

C) DEWFDEESDT

D)SFNQYCGQCN

E) GAVMVAIGIL

36. What is the typical progression of steps in PCR reaction

a) annealing of forward and reverse primers, denaturation of a DNA template, extension by a DNA polymerase using deoxyribonucleotides

b) denaturation of a DNA template , annealing of forward and reverse primers, extension by a DNA polymerase using dideoxyribonucleotides

c) denaturation of DNA template, annealing of forward and reverse primers, extension by a DNA polymerase using deoxyribonucleotides

d) denaturation of a DNA template, annealing of forward and reverse primers, extension by DNA polymerase using ribonucleotides

e) annealing of forward and reverse primers, denaturation of DNA template, extension by a DNA polymerase using ribonucleotides

37. The RNA backbone is susceptible to alkaline hydrolysis due of the

a) inability of RNA to undergo repair

b)presence of modified base

c)presence of ribose rather than deoxyribose

d) presence of uracil rather than thymine

e)singular stranded character of RNA

Answer 1

35. (e)

Explanation: Let us first deduce the three letter sequence of the following 5 peptides:

(a) SerLysAspThrArgGluAsnHisGlnTyr

(b) LysArgHisGlyProArgLysHisArgLys

(c) AspGluTrpPheAspGluGluSerAspThr

(d) SerPheAsnGlnTyrCysGlyGlnCysAsn

(e) GlyAlaValMetValAlaIleGlyIleLeu

Transmembrane domains are formed from bundles of helices that traverse the membrane lipid bilayer. These transmembrane helical regions consist amino acids, predominantly with a hydrophobic character. This sequence feature can be identified in primary sequences using hydrophobicity scales.^[1]

Most common amino acids in transmembrane domain are leucine, isoleucine, valine, phenylalanine, alanine, glycine, serine, and threonine. Note, the number of these amino acids in the sequence (e). The hydrophobic character in the sequence is found to be 68.97%, which is highest among other sequences.

External Link:

1. Online tool for calculating the percentage of hydrophobicity in a given primary sequence of peptide: www.peptide2.com/N_peptide_hydrophobicity_hydrophilicity.php

36. (c)

Explanation: The three sequential steps in the progression of PCR reaction are:

1. Denaturing – double-stranded template DNA template is heated to separate it into two single strands.
2. Annealing – temperature is lowered to enable the DNA primers (forward and reverse) to attach to the template DNA.
3. Extension – the temperature is raised and the new strand of DNA strand is produced using deoxyribonucleotides (dNTPs), MgCl₂ and the Taq polymerase enzyme. The deoxyribonucleotides are the monomers of DNA, or deoxyribonucleic acid.

37. (c)

Explanation: RNA is susceptible to alkaline hydrolysis because the ribose sugar in RNA has a hydroxyl group at the 2’ position compared to DNA, which does not have this 2’ OH group. This hydroxyl (2’ OH) group of the ribose, acts as a nucleophile in the hydrolysis reaction of the RNA.

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