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Mutation (Class - XII)

Description: Proteins
Number of Questions: 15
Created by:
Tags: Proteins Mutation Pleiotropy DNA and its Structure
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Which of the following substitutions would be induced by 5-bromouracil with the highest frequency?

  1. Lys-Tyr

  2. Met-Leu

  3. Met-Thr

  4. Lys-Gln


Correct Option: C
Explanation:

5-Bromouracil induces transitions, not transversions.

Which of the following is a transition mutation?

  1. UAU ACC UAU to UAU AAC CUA

  2. UUG CUA AUA to UUG CUG AUA

  3. C to G

  4. T to A


Correct Option: B
Explanation:

This is a transition mutation because A is mutated to G.

Why are frame-shift mutations more mutating than base substitutions?

  1. Frameshifts are less common than base substitutions.

  2. More than one amino acid are affected by frameshift.

  3. More than one amino acid are affected by base substitutions.

  4. Only one amino acid is affected by frameshift.


Correct Option: B
Explanation:

Frameshift mutation affects more than one amino acid. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame resulting in a completely different translation from the original.

How does base pairing take place after a tautomeric shift in guanine?

  1. Guanine pairs with cytosine.

  2. Guanine pairs with thymine.

  3. Guanine pairs with adenine.

  4. Guanine forms dimer with guanine.


Correct Option: B
Explanation:

Due to tautomeric shift, the more stable keto form of guanine changes to less stable enol form and pairs with thymine.

Loss of a purine base to form an apurinic site results into

  1. spontaneous mutation by deamination

  2. spontaneous mutation by depurination

  3. induced mutation

  4. errors introduced during DNA repair


Correct Option: B
Explanation:

Loss of a purine base (A or G) to form an apurinic site (AP site) is depurination, which results into spontaneous mutation. AP site has neither a purine nor a pyrimidine base, either spontaneously or due to DNA damage.

Which enzyme checks DNA for errors during DNA replication?

  1. RNA polymerase

  2. DNA ligase

  3. DNA polymerase I

  4. DNA polymerase III


Correct Option: C
Explanation:

DNA polymerase I is involved in checking errors during DNA replication and performing excision repair.

Frameshift mutations are induced by

  1. nitrous acid

  2. 5-Bromouracil

  3. Acridine

  4. Ethyl methane sulfonate (EMS)


Correct Option: C
Explanation:

Acridine dyes induce frameshift mutations.

What happens in a tautomeric shift?

  1. Adenine and guanine are changed and can no longer form base pairs.

  2. The purines chemically get mutated to pyrimidines.

  3. Hydrogen atoms move from one position to another position.

  4. Carbon atoms move to form a base with altered properties.


Correct Option: C
Explanation:

In tautomeric shift, hydrogen atoms move from one position in a purine or pyrimidine to another position; for example, from an amino group to a ring nitrogen.

If a codon UAU has mutated to UAG by some mutagenic agent, then which type of mutation has probably taken place?

  1. Mis-sense mutation

  2. Non-sense mutation

  3. Transition mutation

  4. Silent mutation


Correct Option: B
Explanation:

UAU codes for tyrosine and UAG codes for stop codon; so non-sense mutation has taken place.

Which of the following is/are the outcome(s) of pleiotropy?

a. Increased resistance to falciparum malaria in sickle cell anemia b. Abnormal mucus production in cystic fibrosis c. Appearance of delicious apple and navel oranges

  1. only a

  2. only b

  3. a and b

  4. only c


Correct Option: C
Explanation:

In both cases, i.e. falciparum resistance and abnormal mucus production, mutation in one gene results in more than one phenotypic trait. Thus, both are examples of pleiotropy.

A specific 32bp deletion known as CCR5-Δ32 in human CCR5 gene

  1. causes lymphoid malignancies

  2. provides resistance against HIV

  3. causes breast cancer

  4. causes Fanconi anemia


Correct Option: B
Explanation:

Mutation known as CCR5-Δ32 in the CCR5 gene imparts protection against HIV.

A mutation that causes a change in a single nucleotide in DNA

  1. causes the codon to be correct, but the anti-codon to be incorrect

  2. causes protein synthesis to stop

  3. changes the corresponding nucleotide in mRNA, resulting in a different codon

  4. will have no effect on the resulting protein


Correct Option: C
Explanation:

A change in a single nucleotide in DNA changes the corresponding nucleotide in mRNA, resulting in a different codon that codes for a different amino acid.

Genetic drift is provided by

  1. deleterious mutation

  2. beneficial mutation

  3. neutral mutation

  4. nearly neutral mutation


Correct Option: C
Explanation:

A neutral mutation has no harmful or beneficial effect on the organism. Such mutations occur at a steady rate, forming the basis for the molecular clock. In the neutral theory of molecular evolution, neutral mutations provide genetic drift as the basis for most variation at the molecular level.

UV radiations induce mutation by

  1. inversion of base pairs

  2. formation of pyrimidine hydrates

  3. formation of thymine dimers

  4. deletion of a base pair


Correct Option: C
Explanation:

UV radiations induce mutation by formation of thymine dimer. Dimers ultimately perturb the DNA double helix and interfere with accurate DNA replication.

Which organism was used by Muller to induce mutation by X-rays?

  1. Neurospora

  2. Drosophila

  3. Bacteriophage T4

  4. Male lamb


Correct Option: B
Explanation:

Muller used drosophila in his experiments to induce mutation by X-rays in 1927. He was the first to demonstrate that mutations could be induced by an external factor.

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