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Klinefelter’s syndrome is characterized by an extra X chromosome, resulting in a 47, XXY karyotype.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Sex Determination Mutation and Genetic Disorders
Turner’s syndrome results from monosomy of the X chromosome, leading to a 45, XO karyotype.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Sex Determination Mutation and Genetic Disorders
Angelman syndrome results from loss of maternal UBE3A gene expression specifically in neurons due to deletion, uniparental disomy, or imprinting defect affecting chromosome fifteen q eleven to thirteen region. UBE3A is imprinted in brain, expressed only from maternal allele because paternal copy silenced epigenetically by antisense transcript. Absence of maternal contribution causes neurodevelopmental disorder characterized by seizures, ataxia, and happy demeanor. Prader-Willi syndrome arises from loss of paternal contribution in same region, illustrating differential parental expression. Thus Angelman exemplifies genomic imprinting disorder.
Ref: NCBI Bookshelf, GeneReviews: Angelman Syndrome and Genomic Imprinting, UBE3A Locus Regulation
Traditional chromosomal CGH hybridizes differentially labeled genomic DNAs onto normal metaphase spreads, limiting resolution to approximately 5 to 10 megabases because chromosome condensation and optical resolution constrain breakpoint mapping. Microarray CGH, also called array CGH, hybridizes same competitive probe mixture onto thousands of mapped BAC clones, cDNA, or oligonucleotide probes immobilized on glass slides. Since probe genomic coordinates are precisely known and spots are non-overlapping, resolution improves to kilobase level, enabling detection of microdeletions and microduplications invisible on metaphase chromosomes, unlike limitations inherent to PCR, northern blot, or RPA.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
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