During metaphase I, ________
A) crossing over occurs
B) homologous chromosomes line up in the middle of the cell
C) the nuclear envelope breaks up
D) sister chromatids separate and migrate to opposite poles
B
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In a typical human cell, DNA polymerase synthesizes DNA at a rate of approximately 50 nucleotides per second. Human chromosome 1 contains about 250 million base pairs. If a single origin of replication were used, how long would it take the cell to copy this chromosome?
A) less than 24 hours B) 1 to 2 days C) 1 to 2 weeks D) 50 to 60 days E) 110 to 120 days
Which is the most recently evolved embryonic tissue in animals?
a. mesoderm b. ectoderm c. endoderm d. periderm e. epiderm
Which of the following shows seasonal isolation?
A. Frogs mate in the spring and deer mate in the fall. B. The pollen of different species of pine trees mature at different times. C. The tulips bloom earlier in Tennessee than in New York. D. None of these answers is correct.
Most drugs that inhibit the synthesis of the cell wall act by
A) preventing the cross-linkage of NAM subunits. B) blocking the secretion of cell wall molecules from the cytoplasm. C) preventing the formation of alanine-alanine bridges. D) disrupting the formation of the mycolic acid layer of the cell wall. E) preventing the formation of ?-lactamases.