This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Genotypic Changes”.
1. Bacterial chromosome has the capacity to code for ____________ different proteins.
Explanation: It has been estimated that bacterial chromosomes have the capacity to code for approximately 3500 different proteins.
2. Which is the functional unit of inheritance?
Explanation: A gene is a functional unit of inheritance; it specifies the formation of a particular polypeptide as well as various types of RNA. The chromosome is divided into genes.
3. Populations of cells descending from a single cell are known as ____________
c) wild-type cells
d) parent cell
Explanation: Populations of cells descending from a single cell are known as clones but a cell or an organism which shows the effects of a mutation is called a mutant.
4. The replacement of a purine by a pyrimidine or vice versa is known as ____________
c) base-pair substitution
d) missense mutation
Explanation: Transversion is a type of point mutation is the replacement of a purine by a pyrimi-dine or vice versa.
5. Sickle cell anemia is which type of mutation?
a) nonsense mutation
b) missense mutation
c) deletion mutation
d) insertion mutation
Explanation: A good example of a missense mutation in humans is the disease sickle cell ane-mia. A single base substitution in the codon for the sixth amino acid of normal hemoglobin A changes the sixth amino acid from glutamic acid to valine, thus forming the characteristic hemo-globin S of sickle cell anemia.
6. In nonsense mutation, the new mRNA codon specifies the same amino acid as that from the original codon.
Explanation: In neutral mutation the altered gene triplet produces a mRNA codon which specifies the same amino acid because the codon resulting from mutation is a synonym for the original codon.
7. Which of the following mutations result in frameshift mutation?
a) missense mutation
Explanation: Insertion and deletion mutations result in a shift of the reading frame caused by addition or loss of one or more nucleotides.
8. Which of the following mutagen causes a break in the phosphodiester backbone of the nucleic acid?
a) UV light
c) Nitrous acid
d) base analogs
Explanation: When x-rays interact with DNA, the result is usually a break in the phosphodiester backbone of the nucleic acid.
9. Base analogs have the same hydrogen-bonding properties as the normal bases.
Explanation: Although similar in structure, base analogs do not have the same hydrogen-
bonding properties as the normal bases.They can therefore introduce errors in replication which results in mutation.
10. Acridine orange is which type of mutagen?
a) base analog
b) chemical compounds
c) intercalating agents
Explanation: Acridine orange is an intercalating agent that can intercalate between the base pairs in the central stack of the DNA helix and distort the structures and cause subsequent replication errors.
11. Photoreactivation can cause repair of DNA damaged by which of the following mutagens?
a) UV rays
c) Nitrous acid
d) Base analogs
Explanation: Photoreactivation mechanism is used for repairing damage caused by UV radia-tion.A special enzyme designated PRE, induced by visible light, splits or unlinks the dimers formed because of exposure to UV light and restores the DNA to its original state.
12. Which of the following enzyme is used to join the DNA fragments together?
Explanation: Ligase enzyme is used to join the fragments together which are formed by poly-merases to fill in the gaps in the DNA strand.
13. What is the mutation rate for E.coli per bacterium per cell division?
a) 5.8 x 10-6
b) 5.8 x 10-9
c) 5.8 x 10-8
d) 5.8 x 10-7
Explanation: Mutation rate for E.coli maybe given as 5.8 x 10-8 mutations per bacterium per cell division.
Sanfoundry Global Education & Learning Series – Microbiology.
To practice all areas of Microbiology, here is complete set of 1000+ Multiple Choice Questions and Answers.