A rare recessive trait in a pedigree is indicated by which pattern of inheritanc

Question

A rare recessive trait in a pedigree is indicated by which pattern of inheritance? A. vertical B. horizontal C. diagonal D. both vertical and horizontal E. None of these is correct. What is the difference between cross-fertilization and self-fertilization? A. In cross-fertilization the gametes from one plant are used to fertilize the gametes of another plant. B. In cross-fertilization the gametes from one plant are used to fertilize the gametes from the same plant. C. In self-fertilization the gametes from one plant are used to fertilize the gametes from another plant. D. In cross-fertilization insects are used to pollinate the plants while in self-fertilization the investigator pollinates the plants In a dihybrid cross AABB and aabb, what proportion of heterozygotes for both gene pairs is expected among the F2 offspring? A. 1/4 B. 1/2 C. 3/4 D. All are heterozygotes. E. None are heterozygotes. Drosophila melanogaster has four pairs of chromosomes. Sperm from this species are formed by a meiotic process in which homologous chromosomes pair and segregate but do not undergo crossing over. How many genetically different kinds of sperm could be produced by a Drosophila melanogaster male?

Explanation / Answer

Both the alleles are mutant in a recessive trait in a pedigree anlaysis.Both the Parents are unaffected carriers as they may be heterozygous. Thus, it is indicated by horizontal pattern of inheritance affecting only one generation. Self fertilization is fusion of gametes (male and female) in the same plant. Wind and insects are useful as pollinating agents, while in cross fertiliztion there is fusion of gametes from different plants.Therefore, in cross fertiliztion the gametes from one palnt are used to fertilize the gametes of another plant. (A) In a dihybrid cross, sice each parent is homozygous AABB and aabb, the F1 generation is AaBb. For F2 generation four gametes are formed when AaBb heterozygote is self crossed to obtain : AB, Ab,aB,ab. Thus, 3/4th proportion of heterzygotes are expected in F2 generation.

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