Question

What are nucleotides? How do nucleotides contribute to genes and chromosomes?

Why is the trinucleotide sequence, CAG, important in Huntington Disease?

Answer 1

What are nucleotide?

A nucleotide is one of the structure of components or building blocks of DNA and RNA.

A nucleotide is made up of three parts: a phosphate group, a 5-corbon gugar, a nitrogen base.

The four nitrogen base in DNA are adenine, cytocine, guanine and thymine. Rna contain uracil place of thymine.

How do nucleotide contribute to gene and chromosome?

Ans- DNA consist of a specific sequence of nucleotide at a given position on a given chromosome that codes for a specific peotien.

Gene consists of three type of nucleotide sequence:coding region, called axons, which specify a sequence of amino acid.

Why is the trinucleotide sequence CAG important in Huntington diseases?

Huntington diseases is associated with the extension of a CAG trinucleotide repeat in a novel gene. We have assessed 360 HD individual from 259 unrelated families and found a highly significant correlation between the age of onset and repeat length, which account for approximately 50% of the veriation in the age of onset. Significant association were also found between repeat length and age of death and onset of other clinical fitures. Sib pair and parents- child analysis reaveled that the CAG repeats demonstrate only mind instability. Effected HD sibling had significant correction for trinucleotid expansion (r=0.66, p <0.001) which was not apparent for effected perent child pair.