Genetics Exam 2 Chapter 7

If a mutation that inactivated telomerase occurred in a cell what do you expect the outcome to be?

Without functional telomerase, the telomeres would shorten at each replication cycle, leading to eventual loss of essential coding information an death. In fact, some current observations indicate that decline or loss of telomerase activity plays a role in the mechanism of aging in humans.

The DNA polymerases are positioned over the following DNA segment and moving from right to left. If we assume that an Okazaki fragment is made from this segment, what will be the fragment's sequence? label its 5' and 3'

5'...CCTTAAGACTAACTACTTACTGGGATC...3'

If the GC content of a DNA molecule is 48% what are the percentages of the four bases in this molecule?

If the DNA is double stranded G=C=24% and A=T=26%

If four deoxynucleotides showed nonspecific base pairing would the unique information contained in a gene be maintained through round after round of replication? Explain.

No, the information of DNA depends on a faithful copying mechanism/ The strict rules of complementary ensure that replication and transcription are reproducible.

If thymine makes up 15% of the bases in a specific DNA molecule what percentage of the bases is cytosine?

T=15% C=35%

Describe the types of chemical bonds in the DNA double helix.

The DNA double helix is held together by two types of bonds: covalent and hydrogen. Covalent bonds are found within each linear strand and strongly bond the bases, sugars, and phosphate groups. Hydrogen bonds are found between the two strands; a hydrogen bond forms between a base in one strand and a base in the other strand in complementary pairing. These hydrogen bonds are individually weak but collectively quite strong.

It is essential that RNA primers at the ends of Okazaki fragments be removed and replaced by DNA because otherwise which of the following would result?

The RNA would be more likely to contain errors.

What would happen if in the course of replication, the topoisomerases were unable to reattach the DNA fragments of each strand after unwinding the DNA molecule?

The chromosome would become hopelessly fragmented