How do trinucleotide repeats expand?
As shown in the animation, trinucleotide repeats can expand due to slippage during DNA replication. The number of repeats can therefore increase with each cell division. Expanded repeats are also inherited and can grow longer over multiple …
What is a trinucleotide repeat expansion mutation?
Trinucleotide repeat expansion, is a DNA mutation that is responsible for causing any type of disorder classified as a trinucleotide repeat disorder. These disorders are progressive and effect the sequences of the human genome, frequently within the nervous system.
What is trinucleotide repeat in genetics?
Listen to pronunciation. (try-NOO-klee-oh-tide reh-PEET) Sequences of 3 nucleotides repeated in tandem on the same contiguous section of chromosome.
Why does trinucleotide repeat expansion occur?
The mutation, referred to as “trinucleotide repeat (TNR) expansion,” occurs when the number of triplets present in a mutated gene is greater than the number found in a normal gene [1–3]. Additionally, the number of triplets in the disease gene continues to increase as the disease gene is inherited (Fig. 1a).
Where do trinucleotide repeats occur?
Small expansions of pre-mutation alleles in coding and non-coding trinucleotide repeats (TNRs) are observed in both primary spermatocytes and in haploid germ cells. Large deletions of full-mutation-length alleles of non-coding TNRs are observed in dividing spermatogonia.
What are the two major features of trinucleotide repeat mutation?
Clinical and Genetic Features Collectively, the common clinical features of trinucleotide diseases include neurodegeneration, ataxia, mental retardation, and muscle weakness or wasting [1].
What is trinucleotide repeat?
Trinucleotide repeat disorders, also known as microsatellite expansion diseases, are a set of over 50 genetic disorders caused by trinucleotide repeat expansion, a kind of mutation in which repeats of three nucleotides (trinucleotide repeats) increase in copy numbers until they cross a threshold above which they become …
How are trinucleotide repeats detected?
The expanded trinucleotide repeat is identified throughout the procedure using the RED method. Using this approach, two disease genes, the Huntington’s disease gene and the MJD/SCA3 gene, were cloned.
What is the mechanism thought to be responsible for the expansion of trinucleotide repeats?
DNA Expansion Mechanism. DNA expansions that occur within trinucleotide tracts are attributable to the unique biochemical difficulties of performing DNA replication within long stretches of repeat DNA.
Which of these diseases is caused by a trinucleotide repeat expansion?
CAG trinucleotide repeats encoding polyglutamine (polyQ) stretches of expanded pathological lengths are known to produce a family of autosomal dominant inherited neurological diseases including Huntington’s disease, six types of spinocerebellar ataxia (SCA), spinal and bulbar muscular atrophy (SBMA), and dentatorubral …
Which base would be added opposite this rare Tautomer during DNA replication?
Which base would be added opposite this rare tautomer during DNA replication? When the replicative polymerase encounters this rare guanine tautomer, thymine is added to the newly synthesized strand instead of cytosine.