A mutagen that inserts between the stacked bases of a DNA double helix, distorting the DNA to induce single-pair insertions or deletions is called a(n) ________ agent.
A. distortional
B. interspersing
C. insertional
D. intercalating
Answer: D
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In a typical nerve cell, the nucleus is found in the _____
A) cell body B) synaptic terminals C) axonal region D) dendritic region E) synapse
Serratia marcescens bacteria has a gene that regulates red pigment production by cells. A student inoculates two nutrient agar plates of Serratia and incubates one at 25oC and the other at 37oC. Following incubation, the student observes that colonies on the 25oC plate are red while those on the 37oC plate are nonpigmented. Which of the following statements is a logical conclusion based on these results?
A. This is an example of constitutive gene expression. B. Serratia cells undergo a genotypic change that is proportional to changes in temperature. C. Low temperatures cause repression of certain housekeeping genes. D. Serratia genes for pigment production are induced at certain temperatures.
If there are 32 sister chromatids in a normal somatic cell, what is the haploid number for that cell?
A. 16 B. 32 C. 8 D. 64
Investigators decide to analyze the purity of a preparation of antibody molecules using SDS polyacrylamide-gel electrophoresis (SDS-PAGE). On Lane 1 of the gel, they load a sample of the antibody. On Lane 2, they load an antibody sample that has been treated with a reducing agent called mercaptoethanol, which breaks disulfide linkages. Following electrophoresis, they see distinct bands representing polypeptides with molecular weights of 50 kD and 25 kD in Lane 2 and only one band weighing 150 kD in Lane 1. What can the investigators conclude about their antibody based on the results of this experiment?
A.) their antibody preparation was pure; the 50-kD and 25-kD polypeptides are subunits of the mature antibody that were together by noncovalent bonds B.) their antibody preparation as not pure because it contains polypeptides of different molecular weights in Lane 2 C.) their antibody consists of a single polypeptide chain of 150 kD; treatment with mercaptoethanol cleaves the polypeptide backbone at random sites D.) their antibody is composed of subunits (50 kD and 25 kD in molecular weight) that each must include at least one cysteine residue E.) their antibody consists of a single polypeptide chain of 150 kD; treatment with mercaptoethanol cleaves the polypeptide backbone at specific sites