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2. In Neurospora crasa tetrad analysis showed following result + : m :: 6 : 2. The phenomenon involved for above result would be (1) Branch migration (2) Gene conversion (3) Recombination (4) DNA replication

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Neurospora Crassa Tetrad Analysis 6:2 Ratio Gene Conversion

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December 4, 2025
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2. In Neurospora crasa tetrad analysis showed following result + : m :: 6 : 2. The phenomenon involved for above result would be (1) Branch migration (2) Gene conversion […]

1. Holiday junction is observed during: (1) Mitosis (2) Interphase (3) Recombination (4) DNA damage

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Holiday Junction Is Observed During Which Process?

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December 4, 2025
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1. Holiday junction is observed during: (1) Mitosis (2) Interphase (3) Recombination (4) DNA damage The correct answer is: (3) Recombination. Holliday junction is a characteristic intermediate of homologous genetic recombination, especially during […]

37. In which one of the following human disorders, parents or grandparents are said to carry pre-mutations? (1) Down syndrome (2) Fragile X syndrome (3) Klinefelter syndrome (4) Alkaptonuria

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Pre-mutations and Inheritance in Fragile X Syndrome

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37. In which one of the following human disorders, parents or grandparents are said to carry pre-mutations? (1) Down syndrome (2) Fragile X syndrome (3) Klinefelter syndrome (4) Alkaptonuria The […]

36. Somatic recombination was caused by mild exposure to radiation on flies heterozygous for a given allele during specific stages of development and the individuals were allowed to develop. Such individuals are likely to have A. clones of homozygous cells in heterozygous body. B. site specific mutagenesis. C. twin spots, i.e., patches of mutants cells and homozygous wild type cells in heterozygous body. D. tissue specific expression of the given allele. Which of the following combination of answers will be most appropriate? (1) A and B (2) B and C (3) A and C (4) C and D

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Somatic Recombination in Drosophila

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December 4, 2025
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36. Somatic recombination was caused by mild exposure to radiation on flies heterozygous for a given allele during specific stages of development and the individuals were allowed to develop. Such […]

35. Two auxotrophic strains of E. coli: A (met- bio- thr+ leu+ thi+) and B (met+ bio+ thr- leu- thi-) were incubated together for 18 hours in liquid medium and then ~108 cells were plated on minimal medium. Prototrophs were observed at frequency of 1 X 10-7 cells. This may have happened by process of genetic recombination between two strains or by mutation of strains. Which of the following control experiment would help rule out the possibility of mutation? (1) Plating strains A and B directly on minimal medium (2) Growing the mixture of strain A and B for 18 hours and then plating on complete medium (3) Growing strains A and B individually in a liquid complete medium for 18 hours and then plating on a minimal medium (4) Growing the obtained prototroph in a liquid complete medium for 18 hours and then plating them on minimal medium

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Auxotrophic E. coli Strains Recombination vs Mutation Control Experiment

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December 4, 2025
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Two auxotrophic strains of E. coli: A (met– bio– thr+ leu+ thi+) and B (met+ bio+ thr– leu– thi–) were incubated together for 18 hours in liquid medium and then […]

34. Several mutants (1-4) are isolated, all of which require compound E for growth. The compounds A to D in the biosynthetic pathway to E are known; but their order in the pathway is not known. Each compound is tested for its ability.to support .the growth of each mutant (1-4). In the following table, a plus sign indicates growth and a minus sign indicates no growth. Mutant Medium supplemented with compound A B C D E 1 - - - + + 2 - + + + + 3 - - + + + 4 - - - - + What is the order of the compound (A to E ) in the pathway? (1) EDCBA (2) ACDBE (3) EBDCA (4) ABCDE

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Determining Order of Compounds from Mutant Growth Data (A to E)

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Several mutants (1-4) are isolated, all of which require compound E for growth. The compounds A to D in the biosynthetic pathway to E are known; but their order in […]

33. Three E. coli mutants were isolated which require compound 'A' for their growth. The compounds B, C and D are known to be involved in biosynthetic pathway to A. In order to determine pathway, the mutants were grown in a minimal medium supplemented with ONE OF THE COMPOUNDS, A TO D. The results obtained are summarized below: '+' = Growth on medium 'O' = No growth Which of the following equation represents the biosynthetic pathway of A? (1) BCDA (2) CDBA (3) BDCA (4) ACDB

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Decoding E. coli Mutant Pathways

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December 4, 2025
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33. Three E. coli mutants were isolated which require compound ‘A’ for their growth. The compounds B, C and D are known to be involved in biosynthetic pathway to A. […]

Two new chemical compounds X and Y are synthesized in a laboratory and tested for their potency as a mutagen, The nature of the mutation produced by these compounds is tested for reversal by other known mutagens and the following results were obtained: Reversed by new compounds 5-Bromo uracil EMS Hydroxyl amine Acridine orange X Yes Yes No No Y No No No Yes Which statement best describes the nature of the two mutagens? (1) Compound X produces single base substitutions that generate CG to TA transitions and Compound Y produces insertions or deletions (2) Compound X produces insertions or deletions and Compound Y produces single base substitutions that generate CG to TA transitions. (3) Compound X produces single base substitutions that generate CG to TA transitions and Compound Y produces TA to GC transitions. (4) Compound X produces single base substitutions that generate insertions and Compound Y produces deletions.

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Mutagenic Action of Compounds X and Y Explained

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Two new chemical compounds X and Y are synthesized in a laboratory and tested for their potency as a mutagen, The nature of the mutation produced by these compounds is […]

31. A scientist synthesized four new chemicals which had mutagenic potential and named then as Cl, C2, C3 and C4. He tried to analyse the nature of mutations caused by them and obtained the following results: Which one of the following answers describes the mutagenic potential of the chemicals? (1) C1 causes transitions, C2 causes transversions or large deletions, C3 causes transitions and C4 causes single base insertions or deletions (2) C1 causes transversions, C2 causes transitions, C3 causes transversions and C4 causes large deletions (3) Cl cause large deletions, C2 causes transitions, C3 causes transversions and C4 causes single base insertions (4) Cl and C3 causes transversions while C2 and C4 causes transitions

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Mutagenic Potential of Chemicals C1, C2, C3 and C4

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December 4, 2025
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31. A scientist synthesized four new chemicals which had mutagenic potential and named then as Cl, C2, C3 and C4. He tried to analyse the nature of mutations caused by […]

30, A chemist synthesizes three new chemical compounds in the laboratory and names them as X, Y and Z. After analyzing mutagenic potential of all these compounds, the geneticist observed that all are highly mutagenic. The geneticist also tested the potential of mutations induced by these compounds to be reversed by other known mutagens and obtamed the following results Mutation produce by Reversed by Nitrous acid Hydroxyl amine Acridine orange X YES SOME NO Y NO NO NO Z NO NO YES Assumjng that X, Y and Z caused any of the three types of mutations, transition, transversion or single base deletion, what conclusions can you make about the nature of mutations produced by these compounds? (1) X causes transversion; Y causes transition; Z causes single base deletion (2) X causes transition; Y causes transversion; Z causes single base deletion (3) X causes transition; Y causes single base deletion; Z causes transversion (4) X causes transversion; Y causes single base deletion; Z causes transition Mutations produced by Mutation Reversed by 2-amino purine Nitrous Acid Hydroxyl amine Acridine orange C1 YES YES SOME NO C2 NO NO NO NO C3 YES YES NO NO Mutation produce by Reversed by Nitrous acid Hydroxyl amine Acridine orange X YES SOME NO Y NO NO NO Z NO NO YES Assumjng that X, Y and Z caused any of the three types of mutations, transition, transversion or single base deletion, what conclusions can you make about the nature of mutations produced by these compounds? (1) X causes transversion; Y causes transition; Z causes single base deletion (2) X causes transition; Y causes transversion; Z causes single base deletion (3) X causes transition; Y causes single base deletion; Z causes transversion (4) X causes transversion; Y causes single base deletion; Z causes transition

CSIR NET Life Science Previous Year Questions and Solution on Genetics

Nitrous Acid, Hydroxylamine and Acridine Orange with X, Y, Z

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December 4, 2025
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30, A chemist synthesizes three new chemical compounds in the laboratory and names them as X, Y and Z. After analyzing mutagenic potential of all these compounds, the geneticist observed […]

Neurospora Crassa Tetrad Analysis 6:2 Ratio Gene Conversion

Holiday Junction Is Observed During Which Process?

Pre-mutations and Inheritance in Fragile X Syndrome

Somatic Recombination in Drosophila

Auxotrophic E. coli Strains Recombination vs Mutation Control Experiment

Determining Order of Compounds from Mutant Growth Data (A to E)

Decoding E. coli Mutant Pathways

Mutagenic Action of Compounds X and Y Explained

Mutagenic Potential of Chemicals C1, C2, C3 and C4

Nitrous Acid, Hydroxylamine and Acridine Orange with X, Y, Z

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