Cytogenetic Disorders  Numeric Abnormalities  Structural Abnormalities

Numeric Abnormalities  Euploid –Diploid –Polypoid  Aneuploid –Monosomy –Trisomy  Mosaicism

Structural Abnormalities

Cytogenetic Disorders Involving Autosome

Trisomy 21 (Down Syndrome)

Chromosome 22q11 Deletion Syndrome Velocardiofacial syndrome DiGeorge syndrome

Fluorescence In Situ Hybridization (FISH)  Accompanied by karyotyping to increase the power of cytogenetic analysis

Fluorescence In Situ Hybridization (FISH)  Advantages of FISH –Number of chromosomes in interphase  DNA probes that recognize chromosome-specific sequences –Subtle microdeletions  22q11 deletion syndrome –Complex translocations

FISH

Cytogenetic Disorders Involving Sex Chromosomes

Single-Gene Disorders with Atypical Patterns of Inheritance

Triple Repeat Mutations Fragile X Syndrome

CGG repeats: Normal around 29 Premutation Full mutation

Fragile X syndrome  FMR1 gene  FMR protein –RNA-binding protein that regulates protein translation  Higher level of transcripts in the brain and the testis

Leber hereditary optic neuropathy

Mutations in Mitochondrial Gene

Genomic Imprinting

Farid A. Ardalan, MD, AP, CP