MCG - Molecular Basis of inheritance

Question 1

25) Which of the following step is NOT involved in the Hershey and Chase experiment which revealed that DNA is the genetic material?
a) Infect bacteria with a phage
b) Label bacterial DNA with 32P
c) Bacteria cell undergoes lysis
d) Label viral DNA with 32P
e) Radiolabelled DNA enters bacterium

Answer 1

The key step that was not involved in the Hershey and Chase experiment is:

d) Label viral DNA with 32P

In the Hershey and Chase experiment:

a) Infect bacteria with a phage - This step is involved. Bacteriophages were used to infect bacterial cells.

b) Label bacterial DNA with 32P - This step is involved. Radioisotopes, specifically 32P, were used to label the DNA of the bacterial cells.

c) Bacteria cell undergoes lysis - This step is involved. After the infection, the bacterial cells were lysed (broken open) to separate the phage particles from the bacterial debris.

e) Radiolabelled DNA enters bacterium - This step is involved. During the infection, the labeled DNA (either viral or bacterial) entered the bacterium.

So, the correct answer is (d) Label viral DNA with 32P. In the Hershey and Chase experiment, it was the viral protein coat, not the viral DNA, that was labeled to track the fate of the viral genetic material.

Question 2

26) Which of the following molecular side group is NOT found in all of the four nitrogen containing bases of DNA?
a) Amine group
b) Hydroxy group
c) Methyl group
d) Hydrogen group
e) Carbonyl group

Answer 2

b

Amine group (NH2): Present in adenine, guanine, cytosine, and thymine.

Methyl group (CH3): Present in cytosine and thymine
.
Hydrogen group (H): Present in all organic compounds.

Carbonyl group (C=O): Present in cytosine and guanine.

Question 3

29) What is not contained in a dATP molecule?
a) Pyrimidine molecule
b) High energy phosphate groups
c) Nitrogenous bases
d) Glycosidic bond
e) Deoxyadenosine

Answer 3

a

remember, the adenine in ATP is a purine, not a pyrimidine

Question 4

31) Which of the following is not true of human DNA?
a) Nucleotides have polarity
b) DNA polymerase adds nucleotides in the 5’ to 3’ direction
c) Mutations can be passed through progeny
d) Breaking the 3’to 5’ phosphodiester bond liberates inorganic phosphate
e) Shows a regular, repeating structure under non-random diffraction

Answer 4

D

Question 5

32) Which of the following is true about nitrogenous bases in humans?
a) Amount of guanine is always equal to amount of adenine
b) Bonded by electrostatic interactions
c) In DNA structure, they are parallel to the helical axis
d) Act as template in conservative replication
e) Guanine and cytosine always bonded by three hydrogen bonds

Answer 5

c

they are PERPENDICULAR to the helical axis

Question 6

33) What criteria must the structure of DNA meet in order to be a hereditary structure?
a) Must include nitrogenous bases along mononucleotide chain
b) Must be replicated following conservative base pairing
c) Must allow for heritable mutation
d) Must be a double helix structure
e) Must have parallel strands

Answer 6

c

Question 7

34) Each turn of DNA contains _____ nucleotides
a) 3.0
b) 2.6
c) 3.4
d) 10.0
e) 12.0

Answer 7

d

Question 8

35) Function of miRNA
a) Methylation
b) Deadenylation
c) Promoting translation
d) Adenylation
e) Export RNA to ribosomes

Answer 8

b

Question 9

36) What is the phenotype of a woman who has mosaic retinas with patches of defective colour perception?
a) Homozygous recessive
b) X-linked homozygous recessive
c) Homozygous dominant
d) X-linked recessive homozygous dominant
e) X-linked recessive heterozygous

Answer 9

e

Question 10

40) Huntington’s disease is an inherited disease that causes progressive degeneration of nerve cells in the brain. The structure of DNA must therefore have a replication mechanism and must be capable of undergoing mutation. Which of the following is not true about DNA structure:
a) DNA has a 0.34nm internucleotide distance
b) The DNA double helix has a 2.0μm diameter
c) DNA forms a right handed double helix
d) There are 10 nucleotides per turn of DNA
e) The phosphate group is at the 5’ end whilst the hydroxyl group is at the 3’ end

Answer 10

b

Question 11

41) A 37 year old male is in the GP following a suspected Tay-Sachs disease diagnosis. The GP has decided that they would like to genetically test this man. This is done by breaking the cells releasing DNA, separating the DNA, precipitating it and cleaning DNA. After doing so, the DNA backbone can be analysed. The scientist looks for pyrimidines within the backbone - which of the following options are they looking for?
a) Deoxycitidine and Deoxythimidine
b) Deoxycytidine 5’ monophosphate and Deoxythymidine 5’ monophosphate
c) Deoxythymidine 5’ monophosphate and Deoxyadenosine 5’ monophosphate
d) Deoxythimidine and Deoxyadenosine
e) Deoxythymidine 5’monophosphate and Deoxyguanine 5’ monophsophate

Answer 11

A is wrong; these while both pyrimidines, are nucleosides and therefore can’t be in the DNA backbones (backbone needs nucleotides which have phosphate groups attached)

B is correct; these are both pyrimidines and both have phosphates attached, meaning they are nucleotides

C is wrong; these are both nucleotides and they are complementary BUT only thiamine is a pyrimidine (adenine is a purine)

D is wrong; thiamine is a purine, adenine is a pyrimidine and both are nucleotides