Why is Down syndrome the most common trisomy disorder seen among live born infants?
A. The extra alleles from trisomies of larger chromosomes are embryo lethal.
B. Nondisjunction occurs more frequently for chromosome 21 than for any other chromosome.
C. Trisomies resulting from nondisjunction express fewer alleles than trisomies that result from unbalanced translocations.
D. The incidence may not be truly higher but is recognized more often because the
Answer: A. The extra alleles from trisomies of larger chromosomes are embryo lethal.
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Why is Taq polymerase required to perform a polymerase chain reaction (PCR)?
A. Taq polymerase is heat stable and can therefore withstand the high temperature steps required of PCR that most other enzymes cannot tolerate. B. Taq polymerase is more efficient than other polymerases. C. Taq polymerase is pressure stable and can therefore withstand the high pressure steps required of PCR that most other enzymes cannot tolerate. D. Taq polymerase makes fewer errors than other polymerases. E. All of the choices are correct.
Understanding the risks in participating in a clinical trial and agreeing to participate is known as ________
A) the placebo effect B) the drug affect C) informed consent D) drug-drug interaction E) a double-blind study
The most common spacing is random dispersion
____________________ Indicate whether the statement is true or false.
Which of the following is not true of heterochromatin?
a. It is highly condensed chromatin. b. There are two forms of it, called constitutive and facultative heterochromatin. c. It is transcriptionally active. d. It is largely localized to the nuclear periphery.