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1. The dihybrid F2 ratio 9:7 represents (1) Dominance (2) Independent assortment (3) Epistasis (4) Co-dominance

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Understanding the Dihybrid F2 Ratio 9:7 and Its Genetic Significance

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December 1, 2025
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1. The dihybrid F2 ratio 9:7 represents (1) Dominance (2) Independent assortment (3) Epistasis (4) Co-dominance Explanation of the Dihybrid F2 Ratio 9:7 The dihybrid F2 phenotypic ratio 9:7 is […]

25. Recessive lethal alleles are never completely eliminated from the population because: (1) lethal alleles are always conditional in nature. (2) lethal alleles have selective advantage. (3) they are maintained in the population as heterozygotes. (4) lethal alleles protect organisms from other deleterious mutations.

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Why recessive lethal alleles persist in populations

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November 30, 2025
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Recessive lethal alleles are never completely eliminated from the population because: (1) lethal alleles are always conditional in nature. (2) lethal alleles have selective advantage. (3) they are maintained in […]

24. Across is made between Drosophila stocks, each with an independent mutant allele, resulting in white eye color. The mutant alleles (named w1 and w2) are recessive. X- linked and caused by a deletion in the w+ allele. The wild type phenotype is red eye color. The F1 females are then crossed with wild type mates. In the progeny. all females have red eye color, 1 out of 10,000 males was observed to have red eye color. while the remaining had white eyes. Which one ot the following could possibly expiainthe occurrence of red eyed males in the progeny? (1) One of the mutant alleles has a high rate of spontaneous reversion (2) There is an intragenic recombination between the w1 and w2 alleles during meiosis of F1 (3) There is non-disjunction of X-chromosome during meiosis of F1 females (4) The w1and w2 alleles show intragenic complementation in red eyed mates though it is a rare event.

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Why rare red‑eyed males appear from crosses between two white mutants in Drosophila

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November 30, 2025
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24. Across is made between Drosophila stocks, each with an independent mutant allele, resulting in white eye color. The mutant alleles (named w1 and w2) are recessive. X- linked and […]

23. T4 phages were plated on three E. coli bacterial plateslabelled I,II and III. The phenotypes obtained aredepicted in the picture below. The black spotsrepresent plaques. The following combination of conditions were given to explain the results obtained: Plate Bacterial strain rll locus I i. either B or K-12 a. Wild type II ii. B b. mutant III iii. K-12 From the options listed below, select the one that accurately lists the E.coli strain type ans the corresponding rll locus type. (1) I-iii-a, II-ii-b, III-iii-a (2) I-ii-b, II-i-a, III-iii-b (3) I-i-b, II-iii-b, III-ii-a (4) I-ii-b, II-ii-a, III-ii-b

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Identifying bacterial strain and rII locus type from T4 plaque patterns

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November 30, 2025
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T4 phages were plated on three E. coli bacterial plateslabelled I,II and III. The phenotypes obtained aredepicted in the picture below. The black spotsrepresent plaques. The following combination of conditions […]

22. Wild type T4 bacteriophage can grow on Band K strains of E. coli forming small plaques. rll mutants of T4bacteriophage cannot grow on E. coli strain K (non- permissive host), but form large plaques on E. coli strain B (permissive host). The following two experiments were carried out: Experiment l: E. coli K cells were simultaneously infected with two rllmutants (a- and b-). Several plaques with wild typemorphology were formed. Experiment II: E. coli B cells were simultaneously infected with thesame mutants as above. T4 phages were isolated fromthe resulting plaques and used to infect E. coli K cells.Few plaques with wild type morphology were formed. Which one is the correct conclusion made regarding therll mutants. a- and b- from the above experiments? (1) The mutations a- and b- belong to two differentcistrons (experimentl) and there is norecombination between them (experiment ll). (2) The mutations a- and b- belong to two differentcistrons (experiment l) and they recombined(experiment ll). (3) The mutations a- and b- belong to two differentcistrons (experiment ll) and they recombined(experiment l). (4) The mutants a- and b- belong to the same cistron(experiment l) and they did not recombine(experiment ll).

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Complementation and recombination of rII mutants a– and b– in T4 phage

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November 30, 2025
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22. Wild type T4 bacteriophage can grow on Band K strains of E. coli forming small plaques. rll mutants of T4bacteriophage cannot grow on E. coli strain K (non- permissive […]

21. upon studying a considerable number of different crosses in Drosophila, Morgan reached the conclusion that all genes of this fly were clustered into four linked groups corresponding to the four pairs of chromosomes. Further studies revealed that linkage is not absolute and it is broken frequently. It is broken in prophase by a process called (1) Recombination. (2) Jumping of genes. (3) Integration. (4) Mutation.

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How linkage is broken during prophase in Drosophila

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November 30, 2025
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21. upon studying a considerable number of different crosses in Drosophila, Morgan reached the conclusion that all genes of this fly were clustered into four linked groups corresponding to the […]

20. The concept of recon was proposed by Seymour Benzerby studying recombination between (1) lysis mutants of bacteriophage T4 (2) white eye mutants of Drosophila melanogaster. (3) biochemical mutants of Neurosporacrassa. (4) auxotrophic mutants of Escherichia coli.

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Benzer’s recon concept from T4 rII lysis mutants

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November 30, 2025
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20. The concept of recon was proposed by Seymour Benzerby studying recombination between (1) lysis mutants of bacteriophage T4 (2) white eye mutants of Drosophila melanogaster. (3) biochemical mutants of […]

19. How many complementation groups do the following mutants m1 to m6 come under? Result of complementary between different mutants m1 m2 m3 m4 m5 m6 m1 - - + + - + m2 - + + - + m3 - - + + m4 - + + m5 - + m6 - (1) Two (2) Four (3) Five (4) Three

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How many complementation groups do mutants m1–m6 form?

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November 30, 2025
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How many complementation groups do the following mutants m1 to m6 come under? Result of complementary between different mutants m1 m2 m3 m4 m5 m6 m1 – – + […]