What mechanical and blood flow events occur in left ventricle during the T wave? What valves open or close and why?
What will be an ideal response?
Answer: The T wave is ventricle repolarization. During this time, the ventricle is in diastole (relaxed). The aortic valve is closed by the higher pressure in the aorta than the ventricle. When the pressure in the ventricle drops below that of the atria, the atrio-ventricular valves open, and blood flows into the ventricles from the atria.
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Which of the following best describes the development of sexual structures in mammals?
A. Embryos develop male structures only once the SRY gene on the Y chromosome. becomes active; if SRY is not present, they develop female structures. B. Embryos initially develop female structures, but these degenerate and male structures develop once SRY becomes active. C. Embryos initially develop both male and female structures; once SRY becomes active, female structures degenerate and male structures continue to develop. D. Embryos initially develop male structures; if SRY is not present, these degenerate and female structures develop. If SRY is present, they continue to develop. E. None of these accurately describes the development of sexual structures in mammals.
Which of the following biotechnology applications of site-specific recombination deletes DNA from the target?
A. gene activation by removing a transcriptional stop site B. gene insertion C. allele replacement D. gene activation by adding an enhancer sequence E. gene repression by disrupting transcription with an insertion.
Some viruses have the ability to stimulate uncontrolled growth of the host cells, resulting in cancer. Which virus has oncogenic properties?
a. Measles b. Papilloma c. Retroviruses d. Influenza
If an individual has the genotype YyZz what gametes could it produce?
a. YyZz b. Yz, yZ, Yz, or yz c. Yy or Zz d. Y, y, Z, or z