How did the cessation of crossing-over contribute to the disparity between the X and Y chromosomes? What will be an ideal response?
ANSWER: In most chromosomes, crossing-over is a way to make sure that subtle changes are regularly
exchanged and that major differences do not accumulate. In the X and Y chromosomes, the
slow accumulation of a region in which crossing-over did not occur prevented genetic
exchange between the two and resulted in each evolving differently. It is very similar to
taking a population and separating it - each will accumulate its own unique mutations and
these will slowly create a significant difference between the two.
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During the cardiac cycle, when a heart chamber is relaxed, it is in ____________________ and when it is contracting, it is in ____________________
Fill in the blank(s) with correct word
Enzymes used to cut DNA molecules in recombinant DNA research are
a. ligases. b. restriction enzymes. c. transcriptases. d. DNA polymerases. e. replicases.
Explain how and why the following circumstances influence characteristics of temperature-induced DNA melting:
percentage of GC base pairs urea (forms hydrogen bonds with bases) sodium chloride (neutralizes negatively charged phosphates) What will be an ideal response?
The number of chromosome pairs in a species:
a) is always 23. b) is greatest among insects. c) is always greater than three. d) increases with intelligence. e) None of the above are true.