Describe the process of recombination-repair
What will be an ideal response?
Ans: Recombination-repair systems are used when a structural distortion, such as a thymine dimer, is skipped during replication, leaving a gap in the newly synthesized strand opposite the distortion. A normal template sequence must be retrieved from a normal duplex copy; in E. coli, this would be the other daughter duplex following replication of that region, but before the completion of replication and segregation of the two daughter chromosomes. This retrieval is accomplished by a single-strand exchange from the normal duplex to fill the gap in the damaged duplex. The resulting gap in the normal copy is then repaired by a DNA polymerase and DNA ligase, and the original damaged site must also be repaired before the next replication.
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You begin an experiment involving metabolic processes in human liver cells, but you discover your liver tissue samples have been contaminated with a strain of obligate anaerobic bacteria. Theoretically, how could you kill the bacteria while minimizing damage to the liver cells?
a. soak the tissue samples in pure ethanol b. put the sample through an autoclave c. expose the samples to gaseous oxygen d. dehydrate the tissue samples overnight
Copernicus, Galileo, and Darwin found that
____ caused their science to be controversial. a. prevailing belief b. objective data c. astronomy d. the supernatural e. experimental design
In order to infect a cell, a virus must
A. have a special protein on its surface that can interact with a protein receptor on the surface of the host cell. B. produce a special extension of its cytoplasm when it comes into contact with the appropriate host cell. C. inject its protein into the cell while the nucleic acid remains attached to the host cell surface. D. active burrow through the cell wall or cell membrane of the host cell to reach the cell's nucleus.
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
A) sequence of bases B) phosphate-sugar backbones C) complementary pairing of bases D) side groups of nitrogenous bases