Which chromosome is involved in Angelman syndrome?
Ans. is 'b' i.e., chr 15 Genomic imprinting* A person inherits two copies of their genes, one from mother and one from father. Usually both allels of gene are active in cells. However, in some cases, one of the allel (either maternal or paternal) is silenced and only the counterpart remains active.* When the allel inherited from mother is silenced/inactivated (paternal allel is active), it is called maternal genomic imprinting. When paternal allel is silenced (maternal allel is active) it is called paternal genomic imprinting.* Thus genomic imprinting leads to preferential expression of an allel depending on its parental origin.* Important examples of genomic imprinting are1) Prader Willi syndrome# It is due to paternal genomic imprinting in which there is deletion on paternal chromosome 15.# They are characterized by hypotonia, obesity, short stature, mental retardation, hypogonadism, hyperphagia, and short hand and feet.# There is decrease in GnRH, LH, FSH and GH. Ghrelin levels are raised.2) Anglemann syndrome# It is due to maternal genomic imprinting in which there is deletion on maternal chromosome 15.# They are characterized by hypotonia, mental retardation, seizures, ataxia, and inappropriate laughter (Happy puppets).
chr 13
chr 15
chr 18
chr 21
Genetics And Genetic Disorders