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A telomere (/ ˈ t ɛ l ə m ɪər, ˈ t iː l ə-/; from Ancient Greek τέλος (télos) 'end' and μέρος (méros) 'part') is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes (see Sequences). Telomeres are a widespread genetic feature most commonly found in eukaryotes.
Measurements of telomere lengths across cell types at various ages suggest that this gradual chromosome shortening results in a gradual reduction in telomere length at a rate of approximately 25 nucleotides per year. [3]
Telomerase, also called terminal transferase, [1] is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most eukaryotes. Telomeres protect the end of the chromosome from DNA damage or from fusion with neighbouring ...
The first complete telomere-to-telomere sequence of a human autosomal chromosome, chromosome 8, followed a year later. [72] The complete human genome (without Y chromosome) was published in 2021, while with Y chromosome in January 2022. [3] [4] [73] In 2023, a draft human pangenome reference was published. [8]
As the cell divides, the telomeres on the ends of chromosomes shorten. The Hayflick limit is the limit on cell replication imposed by the shortening of telomeres with each division. This end stage is known as cellular senescence. The Hayflick limit has been found to correlate with the length of the telomeric region at the end of chromosomes.
With each division the cells telomeres, protective sequences of DNA on the end of a chromosome that prevent degradation of the chromosomal DNA, shorten. This shortening has been correlated to negative effects such as age-related diseases and shortened lifespans in humans.
She told me I walk 3.14 meters per second because I completed the test in 1.91 seconds. That is faster than average for my age group, and certainly breezier than most of her patients in their 60s ...
This is sometimes called the "end replication problem". If a cell did not contain telomeres, genetic information from the DNA on the ends of chromosomes would be lost with each division. However, because chromosomes have telomeres or mega-telomeres on their ends, repetitive non-essential sequences of DNA are lost instead (See: Telomere shortening).