Answer:
Testcrosses clarify linkage because each phenotypic class of progeny corresponds to each gamete type produced by the dihybrid parent.
Explanation:
- A test cross involves the crossing of an individual with another phenotypically recessive individual so as to determine the zygosity of the former by analyses of the proportions of offspring phenotypes.
- In order to determine linkage, the test cross shows that if the parentals are more than the recombinants, we can say that the two genes such as b and c are genetically linked and therefore, they must be on the same chromosome.
- Also, the test-crosses help to find out which alleles came from which parent.
- By setting up testcrosses in which one parent is homozygous for the recessive alleles of both genes,we can analyze the gene combinations received in the gametes from the other, doubly heterozygous parent.
Http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072434/
There is a website with some info. Hope it helps! :)
I'm almost positive it's B (<span>B. It must be compacted and/or cemented</span>, but it's been along time since this subject..... Hope this helped.
Answer:
1→4→5→3→2
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Mitotic cell division starts with the condensing of chromosome accompanied by splitting of the centrosome and its movement towards the opposite poles.
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As the nuclear envelope and nucleolus disappear, spindle fibres arise from the centrosomes and start binding to the condensed chromosomes at the centromeres.
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The chromosomes bound by the spindle fibers are then arranged in the middle of the cell forming the equatorial metaphase plate.
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Next the centromere splits and the sister chromatids are pulled away towards the poles by the contraction of spindle fibres.
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Following this, a cleavage furrow starts to develop in the middle of the cell while the nuclear membrane starts to reappear around the separated chromatids.
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The condensed chromatids start thinning into chromatin fibre along with reappearance of the nucleolus and the cleavage furrow deepening further.
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Finally as the nuclear membrane becomes fully intact, the cleavage furrow deepens and split the cells from middle into two daughter cells.