Question

What is unique about the structure of telomerase that allows it to extend the ends of chromosomes?

Short answer

Answer: The unique properties and components of telomerase that enable it to extend the ends of chromosomes include the reverse transcriptase activity of its TERT protein subunit, the built-in template for telomere synthesis provided by its RNA component TERC, and the processivity of the enzyme, which allows it to efficiently elongate chromosome ends by synthesizing multiple telomere repeats before dissociating.

Step-by-step solution

Introduction to telomerase

Telomerase is an enzyme that plays a crucial role in maintaining the length of chromosomes by adding repetitive DNA sequences (telomeres) to the end of chromosomes, thus preventing the loss of genetic information during cell division. To understand what's unique about telomerase's structure, let's explore its components and how it extends the ends of chromosomes.

Components and structure of telomerase

Telomerase is composed of two main parts: the telomerase reverse transcriptase (TERT) protein subunit and an RNA component called telomerase RNA component (TERC). TERT is the catalytic subunit with reverse transcriptase activity that adds DNA nucleotides to the ends of chromosomes, while TERC serves as a template for the synthesis of the telomere repeats.

The reverse transcriptase activity of TERT

Reverse transcriptases are enzymes that can synthesize DNA from an RNA template, which is opposite to the usual process of transcription occurring in cells (where RNA is synthesized from a DNA template). TERT is a specialized reverse transcriptase enzyme that elongates telomeres using TERC as a template. This reverse transcriptase activity allows telomerase to synthesize telomere repeats at the ends of chromosomes.

TERC as a built-in template for telomere synthesis

The RNA component of telomerase, TERC, contains a sequence that serves as a template for the synthesis of telomere repeats. This means telomerase carries its own built-in template for the specific telomeric DNA sequence it needs to add to the ends of chromosomes. Having an internal template allows telomerase to accurately synthesize the telomere repeats, which ensures proper maintenance of chromosomes.

Processivity of telomerase

Another unique feature of telomerase is its processivity, which refers to the ability of an enzyme to catalyze multiple reactions without releasing its substrate. In the case of telomerase, it repeatedly extends the same chromosome end by synthesizing multiple telomere repeats before dissociating. This processivity is essential for the efficient elongation of chromosome ends.

Conclusion: Unique structure of telomerase for chromosome extension

In summary, the structure of telomerase that allows it to extend the ends of chromosomes is unique due to these factors: 1. The telomerase reverse transcriptase (TERT) protein subunit has the reverse transcriptase activity responsible for synthesizing telomere repeats. 2. The telomerase RNA component (TERC) acts as a built-in template for the synthesis of telomere repeats. 3. The processivity of telomerase allows it to efficiently elongate chromosome ends by synthesizing multiple telomere repeats before dissociating.