For an individual with the XXXY chromosomal composition, the expected number of
ID: 164838 • Letter: F
Question
For an individual with the XXXY chromosomal composition, the expected number of Barr bodies in interphase cells is _____ variable one two three zero Inactivation of X chromosome is random in the embryotic stem cell in the early development stage; later, all descendant cells have same inactivation. This is the reason how Calico cats show black and yellow-orange patches of fur color due to activation of different fur color genes in different areas of cells How do you call the hypothesis for this phenomenon? Null hypothesis Alternate hypothesis Lyon hypothesis Mendel hypothesis Lion hypothesis Which cross below can identify X-linked genes? Test crosses Reciprocal crosses Monohybrid crosses Dihybrid crosses Which statement below is incorrect? Linked genes are certain genes which segregate as if part of same chromosome and are inherited as single unit Synapsed chromosomes reciprocally exchange segments-reshuffle (recombine) alleles between homologs The frequency of crossing over between two genes is proportional to the distance between them. Genes show linkage if on different chromosome Genes assort independently if on different chromosomes. Which statement below is incorrect? Percentage of offspring resulting from recombinant gametes depends on distance between two genes on chromosome Linked genes exist in a linear order along the chromosome and variable amount of exchange occurs between any two genes during gamete formation. Two genes located relatively close to each other along chromosome are less likely to have chiasma formed between them, and less likely to have crossover occurred. Complete linkage produces parental or noncrossover gametes in equal proportions When Two linked genes with loci far apart, number of recombinants can exceed 50%Explanation / Answer
Explanation:-
23.
(B) part answer ie one
In normal females only one X chromosome will remains active and any additional ones are inactivated during development (after about 10 embryonic divisions). The inactivated X chromosome forms a small dark staining spot in nucleus is called a Barr body.
24.
(C) part answer ie Lyon hypothesis
Mary Lyon's proposing random inactivation in early embryonic life of one of the two X chromosomes in the cells of mammalian females, provides an opportunity to remember and celebrate the work of those involved. . Alongside the hypothesis itself, previous cytological studies of mouse and human chromosomes, and the observations on X-linked mutants in both species deserve recognition for their essential role in underpinning the hypothesis of random X-inactivation, while subsequent research on the X-inactivation centre and the molecular mechanisms underlying the inactivation process represent some of the most outstanding contributions to human and wider mammalian genetics over the past 50 years.
25.
(B) part answer ie Reciprocal cross
It is the breeding experiment which is designed to test the role of the parental sex on a given inheritance pattern ie (X linked genes).All parent organisms must be true breeding to properly carry out such an experiment. In this one cross a male expressing the trait of interest will be crossed with a female not expressing the traits.
26.
(C) part answer is incorrect
The frequency with which the crossing over occurs between any two linked genes is proportional to the distance between the loci along the chromosomes.
27.
(E) part answer
Recombinant frequency can never exceeds 50 % when two linked genes with loci far apart . This is non intuitive because one imagines that as long as the chromosomal distance increases then more crossovers occur and more recombinants will be produced. So for long chromosomal regions there will be no zero class and so the recombinant frequency will be 50 percent but will never exceed this.
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