Question

you are task with sequencing the DNA of a patient. Upon completion you discover that this patient lacks the TTAGGG repeats that are normally found at the end of linear chromosomes. What are 3 possible deleterious results that may arise from this condition?

Answer 1

The 5'TTAGGG3' repeating sequences are called telomeres. Telomerase replaces short bits of DNA(telomeres) which are otherwise shortened during mitosis.

1. Under normal circumstances when telomerase is absent and telomeres are not replaced, cells divide recursively and reach their Hayflick Limit at some point in the progeny whereby cells become senescent and cell division ceases leading to premature aging and death.

2. Cri du chat syndrome is caused by Loss of distal arm of chromosome 5, where telemeres are located. Loss of one copy of TTAGGG is considered as the reason for the syndrome.

3 . mutations in TTAGGG subunits can lead to a critical bone marrow disorder called Dyskeratosis congenita.