When performing in vitro mutagenesis, a vector is used that may contain a positive marker (e. g., a gene for resistance against the antibiotic neomycin) and a negative marker, such as the thymidine kinase gene. cells that carry the latter will die when exposed to a drug called ganciclovir. if a researcher exposed stem cells to a targeting vector with these two markers, and subsequently treated them with neomycin and then ganciclovir, which would be true of the surviving cells? a. any surviving cells will have been correctly targeted (i. e., the gene of interest will have been removed).b. half of the surviving cells will still contain the gene targeted for inactivation, whereas in the remaining half this gene will have been removed. c. any surviving cells will not carry either the positive or negative markers. d. any surviving cells will still contain the original, targeted gene (i. e., these cells could not be used to generate knockout mice)

How are viruses and bacteria different?

Mouse liver cells were homogenized and the homogenate subjected to equilibrium density-gradient centrifugation with sucrose gradients. fractions obtained from these gradients were assayed for marker molecules (i. e., molecules that are limited to specific organelles). the results of these assays are shown in the figure. the marker molecules have the following functions: cytochrome oxidase is an enzyme involved in the process by which atp is formed in the complete aerobic degradation of glucose or fatty acids; ribosomal rna forms part of the protein-synthesizing ribosomes; catalase catalyzes decomposition of hydrogen peroxide; acid phosphatase hydrolysis monophosphoric esters at acid ph; cytidylyltransferase is involved in phospholipid biosynthesis; and amino acid permease aids in transport of amino acids across membranes. a) name the marker molecule and give the number of the fraction that is most enriched for each of the following cell components: lysosomes; peroxisomes; mitochondria; plasma membrane; rough endoplasmic reticulum; smooth endoplasmic reticulum.

The idea of spontaneous generation was disproved by in a experiment involving jars of meat