This set of Molecular Biology test focuses on “History of DNA as the Genetic Material, Nucleic Acid Molecules Genetic Information”.
1. Which of the following statement is false about DNA?
a) Located in chromosomes
b) Carries genetic information from parent to offspring
c) Abundantly found in cytoplasm
d) There is a precise correlation between amount of DNA and number of sets of chromosome per cell
Explanation: In case of eukaryotes DNA is abundantly found in nucleoplasm which is surrounded by the nuclear membrane. This structure is known as nucleus which is found in the cytoplasmic matrix. In case of prokaryotes DNA is found in a less dense cytoplasmic matrix known as the nucleoid.
2. Which of the following function of DNA is necessary for the purpose of evolution?
Explanation: Mutation facilitates the change of bases within a DNA and if this change encodes for a viable amino acid which in turn may lead to the synthesis of a different protein. This protein exerts a phenotypic character to the organism which may be different from the wild type character or may generate a unique character itself, thus leading to evolution.
3. According to the phenotypic characters of pneumococcus considered in Griffith’s experiment of transformation, which of the following statements are correct?
i) Presence of slime layer
ii) Presence of capsule
iii) Absence of capsule
iv) Type of adhesion
v) Molecular makeup of capsule
Choose the correct option
a) i, ii, iii
b) ii, iii, iv
c) ii, iii, v
d) i, iv, v
Explanation: As the two phenotypic characteristics of importance in Griffith’s experiment of transformation are:-
i) Presence or absence of polysaccharide capsule that surrounds the bacterial cell which is responsible for its characteristic smooth or rough colonies respectively
ii) The type of capsule i.e., the specific molecular composition of the polysaccharide present in the capsule coded by its genome, thus triggering immune response of a specific type.
4. Which of the following combination is a correct observation for the transformation experiment performed by Griffith?
a) Type IIIS (living) + mouse = dead
b) Type IIIS (heat killed) + mouse = dead
c) Type IIR (living) + mouse = dead
d) Type IIIS (heat killed) + type IIR (living) + mouse = living
Explanation: Type IIIS strain means smooth strain of pneumococci which is virulent in nature. If this strain is injected alive in a mouse it is bound to develop the disease and thus fall dead.
5. Fredrick Griffith’s experiment involving Streptococcus pneumoniae lead to the discovery of____________
a) DNA as genetic material
b) RNA as genetic material
c) Protein as genetic material
d) Transforming principle
Explanation: When heat killed virulent (smooth) type bacteria were injected in the mouse along with the living avirulent (rough) type of bacteria the mouse developed the disease, which was an unlikely result. Moreover when the bacteria were isolated from the infected mouse they were found to be of the virulent type. Thus, it was believed that some factor from the heat killed virulent type bacteria transformed the avirulent to virulent type bacteria which was known to be as the transforming principle.
6. Definite results proving DNA to be genetic material was given by __________
a) Fredrick Griffith
b) Hershey and Chase
c) Avery, Macleod and MacCarty
d) Meselson and Stahl
Explanation: Avery, Macleod and MacCarty in their experiment with pneumococcus strains type IIIS and type IIR they performed three separate experimental setups:-
i) Using DNase to degrade DNA
ii) Using RNase to degrade RNA
iii) Using Protease to degrade proteins
Thus, when the separate combinations were injected into mice respectively the transforming principle was found to be DNA.
Note- Only these three enzymes were used as only their subsequent substrates were the main factors which were in conflict to be the genetic material.
7. Which of the following statements regarding the mechanism of transformation in Bacillus subtilis is false?
a) A competent bacteria contains a DNA receptor/translocation complex
b) While translocation of exogenous DNA, both strands gets passage into the cell
c) While translocation of exogenous DNA, only one strand gets passage into the cell
d) The exogenous DNA recombines and incorporates itself in the chromosome of the recipient cell.
Explanation: During the translocation of exogenous duplex DNA, one of its strands gets degraded by deoxyribonuclease (DNase) in the periplasmic space, thus allowing passage to only single stranded DNA molecule into the cell.
8. What were the main criteria taken under consideration for the experiment by Hershey and Chase?
a) DNA contains phosphorus, protein contains sulfur
b) Protein contains phosphorus, DNA contains sulfur
c) Both DNA and protein contains phosphorus and not sulphur
d) Both DNA and protein contains sulfur and not phosphorus
Explanation: DNA contains phosphorus in phosphodiester linkage and do not contain any sulphur. DNA is primarily composed of phosphate, nucleotide bases and deoxyribose sugar. Whereas proteins are composed of sulfur containing amino acids.
9. What combination of radiolabelling is correct in case of Hershey and Chase’s demonstration of DNA as genetic material in T2 bacteriophage?
a) 31P, 35S
b) 31P, 32S
c) 31P, 14C
d) 31P, 12C
Explanation: The two factors considered by Hershey and Chase were the simple composition of T2 bacteriophage, that is, DNA and protein. Thus radiolabelling of only one element was required. 32P and 35S being the two radioactive isotopes, therefore, the combination of either 32P, 32S or 31P, 35S was used.
10. Recently, scientists have developed a procedure in which protoplasts of E. coli could be directly infected with the phage DNA. This process is termed as_________
Explanation: Transfection is the process of introduction of exogenous, naked and purified nucleic acid in any organism. In case of transformation the introduction of nucleic acid is via a plasmid or any such vector. Transduction is the process of introduction of nucleic acid via viral vector. Lastly mutation is the alteration of nucleic acid at its composition level, is has nothing to do with DNA transfer.
11. According to Mendel’s experiments gene carry genetic information from parents to offspring’s. On which plant did he perform his experiments?
a) Oryza sativa
b) Pisum sativam
c) Allium cepa
d) Vitis vinifera
Explanation: As we know, Gregor Mendel performed his experiments on garden pea plants whose scientific name is Pisum sativam. The other three scientific names Oryza sativa, Allium cepa and Vitis vinifera belongs to rice, onion and grapes respectively.
12. Plasmids are ____________
a) Double stranded DNA
b) Circular double stranded DNA
c) Linear double stranded DNA
d) Supercoiled circular double stranded DNA
Explanation: Found mostly in prokaryotic cells, plasmids are extra chromosomalauto replicating small circular double stranded DNA which generally carries certain genes for the advantage of bacteria, such as, antibiotic resistance.
13. What stores the genetic information in DNA?
c) Nitrogenous base
Explanation: Genetic information is stored in the sequence of nitrogenous base as they are of four types and they are A, T, G and C. The order of their occurrence decides the mRNA sequence which in turn codes amino acids and leading to synthesis of proteins. Sugars and phosphates form the backbone and are common to all, whereas polymerase helps in the replication of DNA template.
14. DNA always carries the genetic information for all organisms.
Explanation: There are certain viruses in which RNA carries the genetic information. They are known as RNA viruses, for example- retroviruses, influenza virus, etc.
15. What is the major type of RNA produced in the cell required for translation?
Explanation: Generally, rRNA is of 4 types 28S, 5.8S, 18S and 5S. These subunits comprises the 80% of the total amount of RNA produced in a cell and are majorly required for translation as these rRNAs along with proteins form ribosomes which reads the codes for translation.
Sanfoundry Global Education & Learning Series – Molecular Biology.
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