If we think of the DNA double helix as a twisted ladder, what makes up the rungs or steps of the ladder?  

A.  phosphate groups only
B.  alternating phosphate groups and sugars
C.  sugars only
D.  purines and pyrimidines
E.  phosphate groups and bases


D.  purines and pyrimidines

Biology & Microbiology

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The correct sequence for the steps of meiosis I is

A) telophase-anaphase-metaphase-prophase B) 46 chromosomes, 23 chromosomes, then 46 chromosomes C) prophase-metaphase-anaphase-telophase D) anaphase-metaphase-prophase-telophase

Biology & Microbiology

Which action is unable to produce variation?

A. Crossing over B. Random alignment of chromosomes during meiosis C. Asexual reproduction D. Genetic recombination of alleles E. Sexual reproduction

Biology & Microbiology

Without performing any calculations, which of the following is the gene order?

A) abc B) acb C) cab D) +++ E) None of these

Biology & Microbiology

PCR stands for

a. polymerization copying rapidly. b. polymerase chain reaction. c. polymerase copy reaction.

Biology & Microbiology