Concept explainers
Telomerase is an enzyme that is responsible for the addition of telomeric units or repeats to the end of the bacterial chromosome. This enzyme is critical for maintaining the length of the telomere. Mammalian somatic cells lack the activity of this enzyme and therefore, results in the shortening of telomeres in each of the
Explanation of Solution
A phenomenon in which the normal diploid cells end the division process is known as cellular senescence. The somatic cells present in the human as well as the majority of animal exhibit the feature of senescence. Such cells undergo division for a particular number of generations and then cease their activity.
A portion of the telomeres (cap ends of the chromosome) is lost during every division until the complete telomeric region disappears as well as the essential genes are lost. On the other hand, the yeast Saccharomyces cerevisiae is a single-celled microbe that continues to grow as well as it divides throughout its life cycle. Therefore, senescence might be the possible reason for the cessation of telomerase activity in somatic cells.
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Chapter 15 Solutions
GEN COMBO LL PRESCOTTS MICROBIOLOGY; CONNECT ACCESS CARD
- The restriction enzymes Kpn I and Acc 65I recognize and cleave the same 6-bp sequence. However, the sticky end formed from Kpn I cleavage cannot be ligated directly to the sticky end formed from Acc 65I cleavage. Explain why.arrow_forwardThe restriction enzymes KpnI and Acc65I recognize and cleave the same 6-bp sequence. However, the sticky end formed from KpnI cleavage cannot be ligated directly to the sticky end formed from Acc65I cleavage. Explain why.arrow_forwardIn your own words, explain how cancer cells differ from normal cells in regard to the following: Telomeres, which are products of telomerase enzymearrow_forward
- If a mutation that inactivated telomerase occurred in acell (telomerase activity in the cell = zero), what do youexpect the outcome to be?arrow_forwardWhy would replication come to a halt in the absence of topoisomerase II?arrow_forwardUnlike linker DNA and deproteinized DNA, DNA segments wrapped around histone cores are relatively resistant to the hydrolytic actions of nucleases. Explain.arrow_forward
- The 3′ → 5′ exonuclease activity of Pol I excises only unpaired 3′-terminal nucleotides from DNA, whereas this enzyme’s pyrophosphorolysis activity removes only properly paired 3′-terminal nucleotides. Discuss the mechanistic signifi cance of this phenomenon in terms of the polymerase reaction.arrow_forwardWhat is the real definition of DNA ligase to make it truearrow_forwardTrue or false: After chromosomal replication, Type I topoisomerase is used to coil up the double-stranded DNA?arrow_forward
- Extrachromosomal DNA is critical to the antibiotic resistance found in microorganisms, how do these DNA elements account for this phenomena?arrow_forwardTrue/False: RNA polymerase II, with the help of general transcription factors alone, can transcribe heterochromatin.arrow_forwardThe telomeres of a linear chromosome are made of identical directly repeated DNA sequences. How does the enzyme telomerase generate these DNA repeats?arrow_forward
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