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B. Non Mendelian inheritance

Mitochondrial inheritance © SPMM Course of the sons will be affected, and half of the daughters will be carriers. e.g. haemophilia A/B, Duchene muscular dystrophy, and androgen insensitivity syndrome. X-linked dominant disorders These are rare. Similar to X-li...

Trinucleotide expansions © SPMM Course Leber's hereditary optic neuropathy (LHON) is the commonest cause of blindness in young men, with bilateral loss of central vision and cardiac arrhythmias. These diseases are purely maternally inherited. Mitochondrial DNA...

Multifactorial inheritance

Polygenic inheritance

8. Polymorphisms © SPMM Course Multifactorial inheritance It is a complex inheritance in which multiple genes are involved jointly with environmental influences. Most common psychiatric disorders such as schizophrenia do not show a Mendelian pattern of inherit...

9. Cytogenetic techniques © SPMM Course  VNTRs (variable number of tandem repeats). These polymorphisms are the result of varying numbers of repeats in a specific region of a chromosome. These Polymorphisms can be classified according to the length of polymor...

10. Heritability & concordance © SPMM Course known to carry out PCR. It is not error free as laboratory contaminants can have DNA which gets amplified erroneously. The technique has three steps. (1) Double-stranded genomic DNA is denatured by heat into singles...

Specific heritability factors © SPMM Course heritability. Non-additive genetic influences include phenomena such as epistasis – gene-gene interaction, and dominance effects where presence of one gene mitigates the expression of other gene. Heritability can be ...

11. Hardy Weinberg equilibrium © SPMM Course Bipolar disorder 80 Major depression Generalized anxiety Panic disorder Phobia Alcohol dependence *Based on DSM-IIR diagnosis. The estimates must be treated as approximations only. Autism and Tourette’s may have ar...

12. Types of genetic studies

A. Classical genetic studies:

Twin Studies © SPMM Course 12. Types of genetic studies Genetic methods can be classified into four paradigms Basic genetic epidemiology: to quantify degree of familial aggregation and heritability estimates Advanced genetic epidemiology: to explore the mecha...

Family studies © SPMM Course Family studies There are two types of family studies. The family history method is simple but unreliable; here psychiatric history is taken from the probands himself/herself. A comparison can be then made as to how many relatives a...

B. Molecular genetic studies

Linkage analysis © SPMM Course Adoption studies Adoption studies are useful to differentiate the effects of genes and environment. The basic method of the adoption study lies in comparing the rates of disorder in biological relatives and adoptive relatives. Th...

LOD Scores © SPMM Course other locus will also be transmitted to the daughter cell. But linked loci are close enough together so that the chance of a recombination is less than 50%. Thus, their inheritance is not independent. The distance between two loci can ...

Whole genome scan