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After the in depth elaboration of Non-Mendelian Inheritance itself, Maham Afridi sheds light on Non-Mendelian Inheritance: Examples in this sqadia.com medical video lecture. At first, compound heterozygosity is discussed along with congenital hearing loss and tri-allelic inheritance. Later on, information about multi-allelic inheritance, van der woude syndrome, and transposable elements is given. Alongside, genetic anticipation, myotonic dystrophy, and epigenetics are also pursued.
Compound heterozygosity is the presence of two different mutant alleles at a particular gene locus, one on each allele of the pair. In congenital hearing loss, there is a mutations in a gene called connexin 26 or GJB2. Bardet-Biedel Syndrome demonstrates mental retardation, hypogenitalism. Then tri-allelic inheritance is discussed which is a simple autosomal recessive inheritance due to mutations in the BBS 1 gene.
This section primarily focuses on modifier genes. Modifier genes are genes that influence the expression of other genes. Next comes the Van Der Woude Syndrome which is caused by mutations in IRF6 on chromosome 1q32. Multi-locus interactions in cancers is also enlightened here. Transposable elements are migratory segments of the genome. Information about mutations hotspots is also delivered.
Genetic anticipation refers to the apparent worsening of a disorder with subsequent generations. Genetic Anticipation is comprehensively elaborated by Maham Afridi. Pedigree of family with fragile X syndrome is discussed later on. Then light is shed on fragile X mental retardation protein (fmrp). Myotonic dystrophy is genetic anticipation due to an expanding trinucleotide repeat. Disorders caused by expanding trinucleotide repeats are highlighted in the sqadia.com medical video lecture. Furthermore, mechanism of pathogenesis comes under consideration.
Epigenetic mechanisms are those that can change gene expression without modifying the code itself. Types of epigenetic mechanisms include chromatin modifications, DNA methylation, histone modification, RNA-associated silencing, imprinting X-inactivation. After that epigenetic therapies are pursued. Beckwith-Wiedemann Syndrome (BWS) is a recognizable multiple anomaly syndrome is expansively elaborated along with some of the identified cases including Lit1, H19, 11p15, and CDKN1C. Lastly, need for genetic counselling is reported.