9. You have been sitting in the sun a lot lately, though you know full well that the UV in sunlight can cause the formation of pyrimidine dimers (covalent links between adjacent pyrimidine residues) in the DNA of your skin cells. Luckily, skin cells have repair mechanisms that will most likely fix the lesions formed by UV light. Which of the following describes enzymes or mechanisms used in such repair processes? ABC excinuclease recognizes the lesion and cuts out the damaged DNA. RNA polymerase III fills in the damaged area. DNA glycosylases remove the affected bases. The MutH protein marks the strand for repair. 10. Which of the following proteins stabilizes single-stranded regions? DnaA protein DnaB protein SSB Tus
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In this process, the damaged DNA segment is recognized and removed by certain enzymes, and then the gap is filled in by DNA polymerase using the undamaged strand as a template. So, option A (ABC excinuclease recognizes the lesion and cuts out the damaged DNA) is Show more…
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Adi S.
Exposure to UV radiation in sunlight causes DNA changes in skin cells. Why are these changes more harmful when they occur in an individual with xeroderma pigmentosum (XP) than in an individual who does not have this disorder? 1. Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes. 2. XP individuals have significantly more thymines in their DNA than non-XP individuals do. 3. XP individuals' DNA replication machinery incorporates more incorrect nucleotides in new DNA strands than occur in non-XP individuals. 4. Compared to XP individuals, non-XP individuals produce more UV-protecting pigments. Which of the following characteristics allowed Hershey and Chase to determine whether the genetic material was made of DNA or protein? 1. DNA contains phosphorus, whereas protein does not. 2. DNA contains sulfur, whereas protein does not. 3. DNA contains purines, whereas protein includes pyrimidines. 4. DNA contains nitrogen, whereas protein does not. Rank the following mutations with respect to their likelihood of affecting the structure of the polypeptide (from most likely to affect structure to least likely). 1. Insertion mutation in the middle of an intron. 2. Deletion of 3 bases crossing an intron-exon border. 3. Substitution mutation at the third position of a codon. 4. Substitution mutation at the second position of a codon.
Ekampreet P.
You are looking at two fragments of DNA. Both have the sequence CATTCTG on one strand and GTAAGAC on the other. One of the fragments is exposed to UV light, the other is not. What will happen to the fragments and how might these mutations be repaired? a. The fragment exposed to UV light contains thymine dimers. Thymines lying adjacent to each other can form thymine dimers when exposed to UV light. They can be repaired by nucleotide excision. b. The fragment exposed to UV light contains adenine dimers. Adenines lying adjacent to each other can form dimers when exposed to UV light. They can be repaired by nucleotide excision. c. The fragment exposed to UV light contains thymine dimers. Thymines lying parallel to each other can form thymine dimers when exposed to UV light. They can be repaired by nucleotide excision. d. The fragment exposed to UV light contains thymine dimers. Thymines lying adjacent to each other can form thymine dimers when exposed to UV light. They can be synthesized by nucleotide excision.
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