Species evolve continuously over long spans of time according to the concept of
A. punctuated equilibrium.
B. gradualism.
C. developmental evolution.
D. anagenesis.
E. sexual selection.
B. gradualism.
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With modern molecular techniques, it is now possible to completely assemble a genome from a single cell
Indicate whether the statement is true or false.
The Northern leopard frog (Rana pipiens) and Southern leopard frog (Rana utricularia) are morphologically similar, but they do not mate. They sound very different when calling for a mate. Which mechanism may explain why these frogs are listed as separate species?
A. the inability to interbreed because of morphological differences. B. the difference in bone structure and skin color of the organisms. C. DNA sequences of particular genes. D. the habitat of the organisms. E. both the DNA sequences of particular genes and the inability to produce viable offspring.
Meselson and Weigle grew one strain of bacteriophage lambda with alleles A and B in heavy isotopes and another strain with alleles a and b in light isotopes. Both loci are located near the end of the viral chromosome. Which statement best describes their results and conclusions?
A) They visualized the broken chromosomes under a microscope and concluded that DNA was exchanged between light and heavy chromosomes during recombination. B) They found a gradient of all densities of recombinant chromosomes and concluded that DNA was not exchanged between light and heavy chromosomes during recombination. C) They found that some A b genetic recombinants were almost as dense as the A B parent chromosome and concluded that DNA was exchanged between light and heavy chromosomes during recombination. D) They found that some A b genetic recombinants were almost as dense as the A B parent chromosome and concluded that DNA was not exchanged between light and heavy chromosomes during recombination.
Each human ?-globin locus contains two ?-globin genes, ?1 and ?2, and most individuals have two copies of the locus. Which of the genotypes would result in the most severe phenotype? (A"–" represents a deletion allele.)
A) ?1 ?1 / ?2 ?2 B) ?1 – / ?2 – C) ?1 ?1 / – – D) ?1– / ?2 ?2 E) ?1 – / – –