Exam 13: Dna Structure and Replication

The observation that cancer incidence increases sharply with age was one of the first clues that multiple mutations had to accumulate in one cell before cancer arose. If only one mutation were needed to occur in a single cell for cancer to develop, and if the probability of acquiring a mutation is assumed to be a constant that does not change with age, what would you predict to be the relationship between cancer incidence and age?

Refer to the figure above and then answer the question that follows. -What are the base pairing rules of DNA?

What is the relationship between DNA and proteins?

What is the relationship between mutations and cancer?

Read the information below and then answer the questions that follow. In an experiment similar to those by Beadle and Tatum, Neurospora spores were mutated and grown in minimal medium test tubes. Mutants unable to grow without the amino acid "L"were isolated. Compounds A, B, and C are precursors to L. The following data are generated by providing these compounds to the mutants. Data: All strains grow if given compound L. Strains that grow given compound B also grow if given A or C. Strains that grow given compound C do not grow if given only B or A. Strains that grow given compound A will also grow if given C, but not if given only B. -Beadle and Tatum's accomplishment was to show that:

What units are bonded together to make a strand of DNA?

What is one way that incorrect nucleotides are removed from a newly synthesized molecule of DNA?

Read the information below and then answer the questions that follow. In an experiment similar to those by Beadle and Tatum, Neurospora spores were mutated and grown in minimal medium test tubes. Mutants unable to grow without the amino acid "L"were isolated. Compounds A, B, and C are precursors to L. The following data are generated by providing these compounds to the mutants. Data: All strains grow if given compound L. Strains that grow given compound B also grow if given A or C. Strains that grow given compound C do not grow if given only B or A. Strains that grow given compound A will also grow if given C, but not if given only B. -How many enzymes are in the pathway, from the one that modifies the first compound to the one whose product is amino acid L?

Watson and Crick:

One strand of DNA is the template for the synthesis of another strand. What does this mean?

Read the information below and then answer the questions that follow. In an experiment similar to those by Beadle and Tatum, Neurospora spores were mutated and grown in minimal medium test tubes. Mutants unable to grow without the amino acid "L"were isolated. Compounds A, B, and C are precursors to L. The following data are generated by providing these compounds to the mutants. Data: All strains grow if given compound L. Strains that grow given compound B also grow if given A or C. Strains that grow given compound C do not grow if given only B or A. Strains that grow given compound A will also grow if given C, but not if given only B. -Beadle and Tatum:

Refer to the figure above and then answer the question that follows. -If DNA were a single-stranded molecule instead of a double-stranded one, what function(s) of DNA would be much more difficult to carry out?

A point mutation:

Match the scientist and the approximate time frame (decades) of their work with their achievements. -Correlated the production of one enzyme with one gene

Suppose covalent bonds where used to hold two DNA strands together. What sort of problem would this pose for the double helix?

How do new gene alleles appear?

Watson and Crick discovered:

Refer to the figure above and then answer the question that follows. -Which of the following choices is an example of a mutation?

Read the information below and then answer the questions that follow. In an experiment similar to those by Beadle and Tatum, Neurospora spores were mutated and grown in minimal medium test tubes. Mutants unable to grow without the amino acid "L"were isolated. Compounds A, B, and C are precursors to L. The following data are generated by providing these compounds to the mutants. Data: All strains grow if given compound L. Strains that grow given compound B also grow if given A or C. Strains that grow given compound C do not grow if given only B or A. Strains that grow given compound A will also grow if given C, but not if given only B. -The compound B requires only one modification, by one enzyme, to be converted to L.

Given all the bad things that mutations do, it seems counterintuitive that a low rate of mutation is actually good. What good could possibly come of mutation?