GENETICS AND MOLECULAR-BIOLOGY OF TELOMERES

This chapter focuses on the genetics and molecular biology of telomeres. Telomeres consist of a number of DNA sequences, including a simple repeat that is G rich on one strand at the extreme terminus of the chromosome (termed “telomeric repeat”) and more complex repetitive sequences proximal to it (termed “telomere-associated DNA” or “subtelomeric repeats”). For simplicity, the chapter defines telomeres as complex structures at the ends of linear chromosomes that perform several cellular functions. Among the functions proposed for telomeres at least two are vital: protection of the chromosome end from degradation and fusion (termed “capping”) and complete replication of DNA sequences at chromosome ends. Telomeres are also involved in associations with other telomeres and structures within the nucleus, but the functions of these associations are not clearly understood. Although the alternative—that a telomere is a specific DNA sequence—is certainly a testable hypothesis, there is evidence that the “telomeric DNA” repeats play a significant role in chromosome replication. However, there is no evidence that the telomeric DNA performs all functions ascribed to telomeres in any one organism. © 1992, Academic Press Inc.