Question

Question 13 1 pts Which of the following apply to the function of Telomerases (Choose all that apply]: Protect critical gene functions by moving them away from the end of a chromosome Leaves a 3' overhang on linear DNA Leaves a 5' and a 3' overhang on linear DNA Prevent linear chromosomes from shortening after each round of replication Leaves a 5-overhang on linear DNA Question 14 1 pts Which of the following statements are TRUE about thymine dimers? (Choose all that apply.] Repair proteins recognize thymine dimers as a distortion in the DNA backbone. Thymine dimers are non-covalent links between thymidines on opposite DNA strands. Thymine dimers can cause the DNA replication machinery to stall. Thymine dimers are covalent links between thymidines on opposite DNA strands. Thymidine dimers occur naturally as a part of replication.

Answer 1

Ans.

1.

• Maintenanace of the telomers involves the replication of genetic material and protection against DNA damage.
• Telomerase enzyme carry out this activity.
• Telomearse is an RNA dpendent DNA polymerase which use RNA as a template to synthesize DNA.
• It binds to a special RNA molecule containing complementary RNA sequence.
• It increase the 3' overhaning strand of the DNA using complimentary RNA template.
• Normal DNA replication machinery than form a matching complimentary strand upon sufficient stretching of the telomerase strand.

2.

• DNA exposure to UV light results in the DNA damage which ultimately result in the production of may damaged products including cis-syn cyclobutane pyrimidine dimers.
• This driving force for formation of this dimer is a cycloadditon reaction between two adjacent pyrimidine bases, usually thymines,.
• These thymines co-valently fuse with each other by a cyclobutane rig at their 5th and 6th position.
• These dimers block the DNA and RNA polymerases and results in the disruption/inhibition of DNA replication process.
• Transcription - coupled repair and nucleotide-exicion repair (NER) repair this disruption in eukaryots.
• Thymine dimers produce changes in the configuration of DNA backbone such as pinching of phosphate backbone, weak pairing between 5' T and it's compimentary A and tilt and twist in the angle which is absent in normal DNA shape.