Telomeres are found at the ends of eukaryotic chromosomes. Why is telomerase usually active in germ-line cells but not in somatic cells?

Verified step by step guidance

1. Understand the role of telomeres: Telomeres are repetitive DNA sequences at the ends of eukaryotic chromosomes that protect the genetic material from degradation during replication. Each time a cell divides, telomeres shorten due to the inability of DNA polymerase to fully replicate the ends of linear DNA.
2. Learn about telomerase: Telomerase is an enzyme that adds repetitive nucleotide sequences to the ends of telomeres, counteracting their shortening. It is composed of a protein component and an RNA template that guides the addition of telomeric repeats.
3. Recognize the difference between germ-line and somatic cells: Germ-line cells are responsible for passing genetic information to offspring and undergo many divisions over generations. Somatic cells, on the other hand, are the cells that make up the body and typically have a limited lifespan.
4. Understand why telomerase is active in germ-line cells: Germ-line cells require telomerase activity to maintain telomere length across generations, ensuring the integrity of genetic material for reproduction. Without telomerase, germ-line cells would experience telomere shortening, leading to genomic instability and loss of fertility.
5. Explain why telomerase is not active in most somatic cells: In somatic cells, telomerase is usually inactive to limit the number of cell divisions. This helps prevent uncontrolled cell growth, which could lead to cancer. The progressive shortening of telomeres in somatic cells acts as a natural mechanism for aging and cellular senescence.

Key Concepts

Telomeres

Telomeres are repetitive nucleotide sequences located at the ends of eukaryotic chromosomes. They protect the chromosome from deterioration and prevent fusion with neighboring chromosomes. Each time a cell divides, telomeres shorten, which is associated with aging and cellular senescence.

Telomerase

Telomerase is an enzyme that adds nucleotide sequences to the ends of telomeres, effectively extending their length. This enzyme is typically active in germ-line cells, allowing them to maintain telomere length across generations, which is crucial for reproductive success. In contrast, most somatic cells have low or absent telomerase activity, leading to gradual telomere shortening.

Germ-line vs. Somatic Cells

Germ-line cells are reproductive cells that give rise to gametes (sperm and eggs), while somatic cells make up the rest of the body. The activity of telomerase in germ-line cells ensures that the genetic information is preserved for future generations, whereas somatic cells do not require this mechanism, as they do not contribute directly to reproduction.