Question 1

What is the Meaning of Trinucleotide Repeats?

Accepted Answer

Trinucleotide repeats are specific DNA sequences characterized by the repeated occurrence of a three-nucleotide unit, like CAG or CGG, within the genome. These segments are typically stable; however, they can expand abnormally, leading to clinical consequences. Their length influences gene expression and protein function.

Question 2

What is the Context of Trinucleotide Repeats?

Accepted Answer

These repetitive DNA sequences are distributed throughout the human genome, often within or adjacent to genes. While normal, exceeding a specific repeat threshold leads to pathological instability. This instability correlates with a distinct group of genetic conditions, trinucleotide repeat expansion disorders, impacting neurological and muscular systems.

Question 3

What is the Significance of Trinucleotide Repeats?

Accepted Answer

Clinically, expanded trinucleotide repeats are directly linked to the pathogenesis of over 50 inherited disorders, including Huntington's disease and Fragile X syndrome. An expanded repeat sequence often dictates disease onset, severity, and progression, providing crucial information for diagnosis and patient management. Understanding these expansions aids clinician counseling.

Question 4

What is the Mechanism of Trinucleotide Repeats?

Accepted Answer

Expanded trinucleotide repeats cause disease through varied mechanisms, depending on the specific repeat and its genomic location. Some expansions lead to abnormally elongated, toxic proteins, as in polyglutamine diseases. Other expansions may disrupt gene transcription, alter RNA processing, or cause protein function loss, impairing cellular processes and contributing to tissue dysfunction.

Question 5

What is the Application of Trinucleotide Repeats?

Accepted Answer

Genetic testing for trinucleotide repeat expansions is a standard diagnostic procedure for individuals exhibiting consistent symptoms. This testing also applies in presymptomatic or predictive scenarios for at-risk family members, offering critical information for personal and family planning. Such genetic evaluations are typically conducted alongside comprehensive genetic counseling.

Question 6

What is the Metric of Trinucleotide Repeats?

Accepted Answer

The primary metric for assessing trinucleotide repeats involves determining the precise number of repeat units in a specific gene. Molecular genetic techniques, including PCR and Southern blot analysis, measure the length of these repeat sequences. These methods accurately quantify the repeat number, aiding clinical classification based on established thresholds.

Question 7

What is the Risk of Trinucleotide Repeats?

Accepted Answer

Genetic testing for trinucleotide repeat expansions carries inherent psychological and social risks. A positive predictive test for adult-onset conditions can lead to significant emotional distress, anxiety, and depression, often due to limited treatment options. Implications for family dynamics, employment, and insurance necessitate careful pre-test counseling.

Trinucleotide Repeats

Meaning

Context

Significance

Mechanism

Application

Metric

Risk

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