Exam 10: DNA Replication and Recombination

What primary ingredients,coupled with DNA polymerase I,are needed for the in vitro synthesis of DNA?

In ligase-deficient strains of E.coli,DNA and chromosomal replication are unaltered because ligase is not involved in DNA replication.

The Meselson and Stahl experiment provided conclusive evidence for the semiconservative replication of DNA in E.Coli.What pattern of bands would occur in a CsCl gradient for conservative replication?

DNA replication in vivo requires a primer with a free 3' end.What molecular species provides this 3' end,and how is it provided?

Bacteria are dependent on telomerase to complete synthesis of their chromosome ends.

Describe a somewhat extraordinary finding related to the Tetrahymena telomerase enzyme.

Which cluster of terms accurately reflects the nature of DNA replication in prokaryotes?

A nucleosome is a structure associated with the nuclear membrane.It helps maintain a stable relationship between the extracellular matrix and the membrane itself.

Telomerase is an RNA-containing enzyme that adds telomeric DNA sequences onto the ends of linear chromosomes.

What three possible models were suggested to originally describe the nature of DNA replication?

Refer to the following diagram of a generalized tetranucleotide to answer questions (a)through (e). (a)Is this a DNA or an RNA molecule? ________ (b)Place an "X" (in one of the circles in the diagram)at the 3' end of this tetranucleotide. (c)Given that the DNA strand,which served as a template for the synthesis of this tetranucleotide,was composed of the bases 5' - A C A G - 3',fill in the parentheses (in the diagram)with the expected bases. (d)Suppose that one of the precursors for this tetranucleotide was a ³²P-labeled guanine nucleoside triphosphate (the innermost phosphate containing the radioactive phosphorus).Circle the radioactive phosphorus atom as it exists in the tetranucleotide. (e)Given that spleen diesterase (breaks between the phosphate and the 5' carbon)digests the pictured tetranucleotide,which base(s)among the breakdown products would be expected to be attached to the ³²P?

List four enzymes known to be involved in the replication of DNA in bacteria.

Assume that you grew a culture of E.coli for many generations in medium containing ¹⁵N (from the ammonium ion),a heavy isotope of nitrogen.You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm³ (call this sampleA).You then wash the remaining E.coli cells,grow them for one generation in ¹⁴N,and extract the DNA from a portion of the culture (call this sampleB).You let the culture grow for one more generation in ¹⁴N and extract the DNA (call this sampleC)Each sample of DNA (A,B,and C)is then subjected to ultracentrifugation.Present the centrifugation profiles that you would expect under (a)semiconservative replication and (b)conservative replication.(Note: Assume that unlabeled [¹⁴N] DNA has a density of 1.700 gm/cm³.)

The complex of proteins that is involved in the replication of DNA is called a(n)________.

A characteristic of aging cells is that their telomeres become shorter.

In the Meselson and Stahl (1958)experiment,bean plants (Vicia faba)were radioactively labeled so that autoradiographs could be made of chromosomes.

Which terms accurately reflect the nature of replication of the chromosome in E.Coli?

Which of the following terms accurately describes the replication of DNA in vivo?

DNA replication occurs in the 5' to 3' direction; that is,new nucleoside triphosphates are added to the 3' end.

During replication,primase adds a DNA primer to RNA.