Telomeres are found at the ends of eukaryotic chromosomes. How does telomerase assemble telomeres?

Verified step by step guidance

1. Understand that telomeres are repetitive DNA sequences at the ends of eukaryotic chromosomes, which protect the chromosome from degradation during replication.
2. Recognize that during DNA replication, the lagging strand synthesis cannot fully replicate the ends of linear chromosomes, leading to progressive shortening of telomeres.
3. Learn that telomerase is an enzyme that counteracts this shortening by adding repetitive nucleotide sequences to the ends of chromosomes. Telomerase is a ribonucleoprotein, meaning it contains both a protein component and an RNA template.
4. Explore how telomerase uses its RNA template to extend the 3' overhang of the DNA strand. The RNA template within telomerase is complementary to the telomeric repeat sequence, allowing it to base-pair with the DNA and serve as a guide for nucleotide addition.
5. Understand that after telomerase extends the 3' overhang, conventional DNA polymerase and primase can synthesize the complementary strand, completing the telomere extension process and maintaining chromosome integrity.

Key Concepts

Telomeres

Telomeres are repetitive nucleotide sequences located at the ends of eukaryotic chromosomes. They protect the chromosome from deterioration or fusion with neighboring chromosomes, which is crucial for maintaining genomic stability. 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, counteracting their shortening during cell division. It is composed of a protein component and an RNA template that guides the addition of DNA repeats. Telomerase activity is typically high in stem cells and cancer cells, allowing them to divide indefinitely.

Mechanism of Telomere Assembly

The assembly of telomeres by telomerase involves the enzyme binding to the existing telomere and extending it by adding specific DNA sequences. This process is crucial for maintaining telomere length and ensuring that genetic information is preserved during cell division. The mechanism is vital for cellular longevity and plays a significant role in cancer biology.