Exam 15: Dna and the Gene: Synthesis and Repair

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and ________ of the last nucleotide in the polymer.

Recent studies have shown that xeroderma pigmentosum (an error in the nucleotide excision repair process) can result from mutations in one of seven genes. What can you infer from this finding?

Telomere shortening is a problem in which types of cells?

Refer to the treatments listed below to answer the following question. You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infectious agent. I. Treat the substance with enzymes that destroy all nucleic acids and then determine whether the substance is still infectious. II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III. Culture the substance on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then determining whether the substance is still infectious. If you already know that the infectious agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities?

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA replication is highly accurate. It results in about one mistake per billion nucleotides. For the human genome, how often would errors occur?

Researchers found E. coli that had mutation rates 100 times higher than normal. Which of the following is the most likely cause of these results?

Which of the following characteristics, structures, or processes is common to bacteria and viruses?

Viruses ________.

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have ________.

Who performed classic experiments that supported the semiconservative model of DNA replication?

In the figure associated with this question, which of the three types of viruses shown would you expect to include a capsid(s)?

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from xeroderma pigmentosum?

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?

In the accompanying figure, which is the template strand?

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

Semiconservative replication involves a template. What is the template?