How do urea and NaCl influence temperature-induced DNA melting?
What will be an ideal response?
Urea competes for hydrogen bonds; thus, the bases pair with the urea rather than with each other. This weakens the complementary associations that are required to hold the DNA helix together; thus, less heat is required for melting. The sodium of sodium chloride associates with and neutralizes the strong negative charges on the phosphates. The phosphates do not repel each other with the sodium ion present; thus, the double-stranded structure requires more energy to melt.
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Ecdysis is:
A. development of the ectoderm layer in the gastrula B. development of the epidermis from the ectoderm C. disintegration of the ectoderm D. molting E. the feeding tentacles of the Ecdysozoa
The chromosome that plays the largest role in human sex determination is
A. the group of autosomes known as the SRY group. B. the Y chromosome. C. chromosome number 21. D. the X chromosome. E. chromosome number 22.
In which phase of meiosis I do homologues separate?
A) prophase II B) anaphase C) metaphase I D) anaphase I
A signal molecule is also known as a(n) _____.
-key -initiator -protein -receptor -ligand