Pick the correct answer In the plant Arabidopsis thaliana , a geneticist is inte
ID: 212291 • Letter: P
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Pick the correct answer
In the plant Arabidopsis thaliana, a geneticist is interested in the development of trichomes (small projections). A large screen turns up two mutant plants (A and B) that have no trichomes, and these mutants seem to be potentially useful in studying trichome development. (If they were determined by single-gene mutations, then finding the normal and abnormal functions of these genes would be instructive.) Each plant is crossed with wild type; in both cases, the next generation (F1) had normal trichomes. When F1 plants were selfed, the resulting F2's were as follows:
F2 from mutant A: 602 normal; 198 no trichomes
F2 from mutant B: 267 normal; 93 no trichomes
What can be deduced about the trichome mutants?
A man lacks earlobes, whereas his wife does have earlobes. Their first child, a boy, lacks earlobes.
If the phenotypic difference is assumed to be due to two alleles of a single gene, is it possible that the gene is X linked?
Why does an acentric fragment get lost?
It is the result of a paracentric inversion that causes two homologous centromeres to fuse into a dicentric bridge.
In an inversion, is a 5' DNA end ever joined to another 5' end? Explain. Yes, if the DNA ends are modified by certain enzymes. Yes, but it is very rare. No, biochemically, a 5' DNA end can only join with a 3' DNA end. No, inversions disrupt the DNA, making it topologically impossible for a 5' DNA end to join with another 5' DNA end.Explanation / Answer
Q-1 Ans. option-3 no... The DNA backbone has strict 5' to 3' polarity, and 5' ends can only be joined to 3' ends.
Q-2 Ans. option-1 cross with a female of genotype a/a. Do a test cross. if the fly was A/A all the progeny will be phenotypically A. and if the fly was A/a half of the progenywill be A, and haalf will be a.. The use of a/a (recessive individual known as tester) means that it can be ignored because all of the gametes are recessive and do not contribute to the phenotypes of the progeny. Q-5 Ans. option-1. aneuploid. Trisomic refers to third copy of a chromosome that should be present in two copies (2n+1). Q-6 Ans. is option-3. by definition an acentric fragment has no centromere, so it cannot be alligned or moved during meiosis. consequently, at the end of cell division, it gets left in the cytoplasm where it is not replicated.