Why is trisomy 21 seen so often, but other trisomies (such as trisomy 1) are relatively rare?
A) Other trisomies are just as common as trisomy 21, but individuals are healthy and therefore go undetected.
B) Trisomy 21 occurs more frequently than other trisomies because chromosome 21 is very small and more prone to nondisjunction.
C) Trisomy 21 occurs more frequently than other trisomies because chromosome 21 determines the sex of the fetus.
D) Other trisomies are most often lethal; the fetuses are spontaneously aborted.
E) Other trisomies are more likely to be detected by karyotyping and prevented.
D) Other trisomies are most often lethal; the fetuses are spontaneously aborted.
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Match the following nerve locations or functions with the correct division of the autonomic nervous system (sympathetic or parasympathetic) by writing an "S" or "P" next to the phrase
______ accelerate heart rate ______ decrease heart rate ______ dilate pupil ______ constrict pupil ______ stimulate activity of stomach and intestines ______ inhibit activity of stomach and intestines ______ relaxes lung bronchi ______ constricts lung bronchi ______ nerves branch from middle region of the spinal cord ______ nerves branch from the brain and the posterior region of spinal cord What will be an ideal response?
Which of the following is a basic component
of all of the others?
a. cells d. organism b. organs e. organ systems c. tissues
Support for the succession mechanism of tolerance is found in research on plant communities that shows
A. that plants release toxins that prevent other species from establishing. B. succession is random and cannot be predicted by existing species. C. climax communities never form as predicted by Clements. D. succession is determined largely by species that exist in the ground as seeds or old roots. E. competition-tolerant species colonize first.
Every atom of the same element has an equal number of electrons and protons
Indicate whether the statement is true or false