During which stage of the cell cycle would a cell contain the least total amount of DNA? What will be an ideal response?
ANSWER: In the G1 stage, each chromosome exists as a single copy, and is unreplicated. During the S
stage, the chromosomes replicate so there is now twice as much DNA present. Not until the
end of telophase (and after cytokinesis) will this situation revert.
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The immunity of some black Africans to malaria is probably due to their
A. general health. B. cultural practices. C. age. D. genetic background.
When a farmer grows cotton containing the gene for Bt toxin, insects that are resistant (rr) survive and reproduce. These insects were resistant because
A. the insecticide caused mutations to generate resistant alleles. B. they inherited the alleles that made them resistant. C. the insects wanted to survive the insecticide and mutated their DNA. D. by random chance some insects did not die from the insecticide. E. the insects were able to produce gametes that were resistant to the insecticide.
Why is investigating evolutionary relationships by comparing gene sequences more precise than comparing body forms? How do the two methods compare if we consider divergent and convergent evolution?
What will be an ideal response?
Which of the following is/are TRUE of the fertilization envelope?
A. The fertilization envelope is the physical structure responsible for the slow block to polyspermy. B. The fertilization envelope prevents dehydration of the fertilized egg. C. The fertilization envelope arises as a result of the acrosomal reaction. D. The fertilization envelope is the same thing as the jelly layer. E. The fertilization envelope forms when the vitalline layer lifts away from the egg plasma membrane F. None of these are true.