03 DNA Repair

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• not mutation
• actual damage to nucleotides

Depurination, Deamination

Free Radicals

Single Strand

Base

• breaks glycosidic bond, lets damaged base go

• AP: apurinic or apyrimidic

• AP endonuclease: break phosphate bond, create OH group

Nucleotide

• makes sure DNA bases normal before proceed to replication

Mismach

• look for incorrectly placed bases

• different cells with different number of satellites as result of deficiency

Double Strand

Cerebellar ataxia, telangiectasias, and increased risk of sinopulmonary infections constitute a characteristic triad of ataxia telangiectasia. Telangiectasias are described clinically exactly as they are in the question stem - superficial blanching nests of distended capillaries. Ataxia-telangiectasia also predisposes to an increased risk of hematologic malignancies and causes an immune deficiency consisting of both cell-mediated and humoral dysfunction. The immune deficiency primarily manifests as an IgA deficiency and predisposes to infections of the upper and lower airways.

It is an autosomal recessive condition that occurs due to mutation of ATM gene. ATM (Ataxia Telangiectasia Mutated) gene is responsible for DNA break repair. DNA in patients with ataxia-telangiectasia is hypersensitive to X-ray radiation that causes multiple chromosomal breaks.