This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Molecular Basis of Inheritance – DNA”.
1. Who was the first person to analyse factors?
Explanation: The first person to analyse and detect factors was Mendel. In fact, he was the person who gave the term factors. They were detected by following their patterns of transmission from generation to generation.
2. In which year, the mechanism for genetic inheritance reached the molecular level?
Explanation: The quest to determine the mechanism for genetic inheritance reached the molecular level in 1926. The nature of the genetic material was studied at that time and it was realised that DNA is the genetic material for the majority of organisms.
3. What is the full form of DNA?
a) Degenerative acid
b) Deoxyribonucleic acid
c) Deadly nucleic acid
d) Disoriented acid
Explanation: DNA stands for deoxyribonucleic acid. It is a genetic material known for the majority of organisms living on this planet. This substance is responsible for controlling the inheritance of traits.
4. How many types of nucleic acids are present in the living systems?
Explanation: There are two types of nucleic acids present in our living system. These two are:
i. DNA-deoxyribonucleic acid
ii. RNA-ribonucleic acid
They both can express their effects through the formation and functioning of the traits.
5. DNA is the genetic material in all the known viruses.
Explanation: No, DNA is not the genetic material in all the known viruses. It is the genetic material in all organisms except for some viruses, where RNA is the major genetic material like the riboviruses.
6. Which of the following is not a function of RNA?
Explanation: RNA does not behave as a modifier. Instead, it functions as a messenger that carries genetic information. It also acts as an adapter for picking up amino acids and in some cases behaves as a catalytic molecule.
7. Which of the following is not a correct statement with respect to DNA?
a) It is a long polymer
b) It is found in the nucleus
c) It is a basic substance
d) First identified by Friedrich Meischer
Explanation: DNA is not a basic substance. Instead, it is an acidic substance. It was first identified by Friedrich Meischer in 1869. It is also known as a long polymer of deoxyribonucleotides and is found in the nucleus of the cell.
8. Which of the following is the characteristic feature of an organism?
a) Number of RNA
b) Number of protein molecules
c) Length of chromosomes
d) Length of DNA
Explanation: The characteristic feature of an organism is the length of its DNA. The length of the DNA is usually defined as the number of nucleotides or the number of base pairs present in it. As this substance was acidic in nature, Altmann named it as a nucleic acid.
9. How many base pairs are present in Escherichia coli?
a) 9856 bases
b) 4.6 x 106 bp
c) 3.3 x 109 bp
d) 10,000 bases
Explanation: The number of base pairs or the number of nucleotides present in the bacterium, Escherichia coli are 4.6 x 106 base pairs. The number of base pairs present in human beings is 3.3 x 109.
10. How many numbers of nucleotides are present in Lambda phage?
a) 48502 bp
b) 98526 bp
c) 10000 bp
d) 5326 bp
Explanation: The number of nucleotides or the number of bases in Lambda phage are 48502. The genetic material of Lambda phage consists of a double-stranded DNA which is linear in shape.
11. Which of the following is correct with respect to the genetic material of Φ174 bacteriophage?
a) ss DNA, linear
b) ss RNA, linear
c) ss DNA, circular
d) ds DNA, linear
Explanation: The genetic material of Φ174 bacteriophage is single-stranded DNA which is circular in shape. It has 5386 bases or a number of nucleotides. It is a virus that attacks on bacteria.
12. The genetic material of humans is double-stranded DNA which is circular in shape.
Explanation: The genetic material of humans consists of a double-stranded DNA which is linear in shape. The genetic material of the bacterium Escherichia coli is a double-stranded DNA that is circular in shape.
13. How many components are present in the basic unit of DNA?
Explanation: There are three components in the basic unit of DNA which is also known as a nucleotide, and they are:
i. A nitrogenous base: purine or pyrimidine
ii. A pentose sugar: Deoxyribose sugar
iii. Phosphate group.
14. Which of the following statements is correct with respect to purines?
a) Purines are heterocyclic compounds
b) Purines are 7 membered structure
c) Purines are single-ring structure
d) Thymine is an example of purine
Explanation: Purines are a type of nitrogenous bases which are heterocyclic compounds. They are 9 membered and are double-ring structures. Nitrogen is present at the positions-1, 3, 7 and 9 of the ring. Adenine and guanine are the only two examples of purines.
15. Which of the following statement is incorrect with respect to pyrimidines?
b) 7 membered ring
c) Cytosine is an example of pyrimidine
d) Single-ring structure
Explanation: Pyrimidines are not 7 membered rings. Pyrimidines are a type of nitrogenous bases which are heterocyclic compounds with a 6 membered single-ring structure. Nitrogen is present at 1 and 3 positions of the rings. Examples of pyrimidines include thymine, uracil, and cytosine.
16. By which of the following bonds, a nitrogenous base is linked to the pentose sugar?
a) Phosphate bond
b) Ester bond
c) Peptide bond
d) N-glycosidic bond
Explanation: A nitrogenous base is linked to the pentose sugar by an N-glycosidic bond. As a result of this linkage, a nucleoside is formed. Purine nucleosides have 1’-9 glycosidic linkage and pyrimidine nucleosides have 1’-1 linkage.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
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