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  • ICAR and TNAU E-Course Summarized

    Summarized Notes
  • Which one of the following options represents the combination of all correct statements?

    Question: Which one of the following options represents the combination of all correct statements?

    Options:

    A only
    B only
    C only
    C and D

    🔑Key Points:

    • Genetic linkage and mapping of genes:
    -This Question is related to genetic linkage and the mapping of genes on a chromosome based on the frequency of recombination events.
    -Bacteriophages that have two mutations causing different plaque phenotypes, and the genes responsible for these mutations are 9 cM (centimorgans) apart.
    -Genetic linkage refers to the tendency of genes that are physically close on a chromosome to be inherited together more frequently.
    -The closer two genes are, the less likely they are to undergo recombination during gamete formation.
    -Recombination is the exchange of genetic material between homologous chromosomes during meiosis.
    -Based on the provided information, we have to predict the outcome of a genetic cross involving bacteriophages with specific genotypes.
    -The expected proportions of different plaque types are determined by the distances between the genes and the likelihood of recombination events occurring during the mixing and infecting process.

    • Explaination:
    -Cross given c+ m- x c- m+. Since the genes are 9 cM apart means the the genes are linked.
    -Therefore the proportion of parental types (c+ m- and c- m+) will be much larger than the recombinant types (c+ m+ and c- m-).
    -Based on this we can eliminate the proportions given in A and B.
    -Distance between the genes is recombination frequency percentage.
    -9 cM distance means recombination frequency of 9%.
    -Therefore, proportion of each recombinants (c+ m+ and cm-) = 0.09/ 2 = 0.045.
    -So, the proportion of each parentals (c+ m- and c- m+) = (1-0.09)/ 2 = 0.91/2 = 0.455.
    -For statement C, Total = 45+455+455+45 = 1000.
    -Number of each recombinants (c+ m+ and c- m-) = 0.045 x 1000 = 45; Number of each parentals (c+ m- and c- m+) = 0.455 x 1000 = 455.
    -For statement D, Total = 65+ 680+685+70 = 1500. Number of each recombinants (c+ m+ and c- m-) = 0.045 x 1500 = 67.5; Number of each parentals (c+ m- and c- m+) = 0.455 x 1500 = 682.

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