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TELOMERES

TELOMERES. What are telomeres? . A repeating sequence of DNA at the end of a chromosome For example, a common base code sequence found on the ends of one strand of DNA in humans is 5`-TTAGGG-3` It is repeated as many as 2000 times. Function?. They help prevent chromosomes from fusing

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TELOMERES

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  1. TELOMERES

  2. What are telomeres? • A repeating sequence of DNA at the end of a chromosome • For example, a common base code sequence found on the ends of one strand of DNA in humans is 5`-TTAGGG-3` • It is repeated as many as 2000 times

  3. Function? • They help prevent chromosomes from fusing • Prevent DNA degradation • They may play a role in determine the number of times that a cell can divide • They prevent the loss of coding regions of DNA during DNA replication

  4. Why are they needed? • The final RNA primer for the last Okazaki fragment , gets removed but doesn’t get replaced • The last sequence at the end of the parent strand is not copied and shorter • Chromosomes continually shorten and can lead to loss or damage of important genes if telomeres were not in place.

  5. Figure 1.0: DNA replication : Showing how the DNA gets shorter with each successive replication. The last RNA primer is removed but not replaced with DNA nucleotides

  6. After many DNA replications, the telomeres are completely lost and no longer provide protection • The essential portions may be lost during subsequent replications • It may lose ability to grow, metabolize or divide • Call cell senescence • In humans, cells can divide roughly 50 times before its telomers are too short

  7. Figure 2.0: Telomere length decreases with age

  8. Germ line cells (which produce gametes) must continue replicating • They must maintain their genetic integrity generation, after generation • In these cells, an enzyme called telomerase adds more DNA to the shortening telomeres • Stem cells and certain white blood cells show the presence of telomerase.

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