Genetic Disorders

Front 1

Classification of human genetic disorders

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3

Disorders related to mutations in single genes with large effects

Chromosomal disorders

Complex multigenic disorders

Front 2

Single gene defects can follow two patterns of inheritance

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Single gene disorders with classical Mendelian pattern of inheritance

Single gene disorders with atypical pattern of inheritance

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Mendelian Disorders follow 3 patterns of inheritance:

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AD

AR

X-Linked

Front 4

AD Disorders characteristics

Back 4

Expressed in heterozygous state

Affect males and females equally

Both sexes can transmit the disorder

Front 5

Are enzyme proteins affected in AD Disorders?

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No, instead receptors and structural proteins are involved

Front 6

Examples of AD disorders- Nervous system

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Hungtington disease

Neurofibromatosis

Myotonic dystrophy

Tuberous sclerosis

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NF1 chromosomal location

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17q11

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NF2 chromosomal location

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22q12

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NF1 cause

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Defects in neurofibromin 1 protein coded for by neurofibromin 1 gene (which is an example of a tumour suppressor gene that acts through negative RAS signalling)

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NF1 can lead to

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Neuroblastoma, juvenile myeloid leukemia, GIST, phaeochromocytoma, cafe-au-lait spots, optic nerve glioma, malignant peripheral sheath tumours.

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NF2 cause

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Mutations in neurofibromin 2 gene that codes for Merlin protein (which functions in cytoskeletal stability and hippo pathway signalling)

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NF-2 can lead to

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Schawannoma

Meningioma

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Tuberous sclerosis 1and 2 chromosomal location

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9q34 (harmatin protein)

16p13 (tuberin protein)

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Normal function of the proteins

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Work together in a complex that negatively regulates mTOR

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Mutations in the proteins lead to

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Angiofibroma, mental retardation

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Myotonic dystrophy is associated with

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Skeletal muscle weakness, cataracts, endocrinopathies, cardiomyopathy

Front 17

Myotonic dystrophy pathogenesis

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Expansion of CTG triplet repeat in 3' non-coding region of DMPK gene

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Huntington disease is associated with

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Progressive movement disorders and dementia caused by degeneration of striatal neurons.

Front 19

Huntington disease molecular genetics and pathogenesis

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HD is the prototype of polyglutamine trinucleotide repeat expansion diseases.

Gene for HD is HTT located on chromosome 4p16.3 that encodes Hungtingtin protein. Mutant Huntingtin protein forms when there is repeats excess of 6-35 leading to disease

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APKD features

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Large multicystic kidneys (both), liver cysts, berry aneurysms

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APKD genetics

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Mutations in either PKD1(16p13. 3) or PKD2(4q21) genes.

Both alleles of the involved gene have to be non functional.

Mutation in either PKD gene results in disruption of Polycystin 1 and 2 complex leading to disease.