19. A group of cells are ruptured and mixed in a tube to produce a uniform mixture. This is then centrifuged to produce four distinct layers
of cell contents. The material in one of the layers contained a large
amount of protein. What is this layer composed of? *

Why reason best illustrates why hershey and chase chose to use viruses in their experiment?

Dna replication or repair occurs in a cell in all of thw following situations except when

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.