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“Emery’s Elements of Medical genetics”

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1 “Emery’s Elements of Medical genetics”
Textbooks: “Emery’s Elements of Medical genetics” Strachan & Read “Human Molecular Genetics” (for the genome project material)

2 Medical Genetics 1 Causes of human disease: age, environment, genetic factors and combinations of these Using a combination of approaches, rapid progress is now being made in our understanding of the cause of many genetic diseases

3 Classification of Genetic Disease
I - Single gene disorders: Currently over 6,000 different disorders or traits described, including: Cystic fibrosis Fragile X mental retardation Predisposition to colorectal cancer 30,000 different structural genes coded for in the human genome.

4 Classification of Genetic Disease
II - Chromosomal abnormalities trisomy 21 found to be associated with Down syndrome III - Multifactorial disease: Cleft lip and palate Insulin dependent diabetes mellitus Ischaemic Heart disease Cancer




8 Pedigrees and Inheritance
To begin investigating the genetics of a particular disorder: Observe the way condition is transmitted from one generation to the next Study its frequency among relatives

9 Pedigree Drawing Normal male Affected male Normal female Affected female Index case Mating

10 Consanguineous mating (usually between cousins)
Parents with son and daughter (in order of birth) Dizygotic twins

11 Monozygotic twins Sex unspecified Heterozygotes for autosomal genes Carrier of X-linked genes Dead

12 Miscarriage Woman with children by different partners Numbering of pedigree: generations I, II, III…. Individuals in each generation 1, 2, 3,….

13 Mendelian Inheritance
Autosomal Inheritance: due to a mutation in a gene from chromosome 1 to 22 Sex-linked Inheritance: gene on the X (or Y) chromosome Either type may be dominant or recessive

14 Autosomal Recessive inheritance

15 Autosomal dominant inheritance
an affected person usually has one affected parent transmitted by either sex child of an affected parent is at 50% risk of also being affected

16 X-linked dominant inheritance
affects either sex but more females than males females often more mildly affected than males child of an affected female at 50% chance of being affected for an affected male, all his daughters but none of his sons affected Quite rare, examples include an inherited form of rickets (mutation in an endopeptidase gene)

17 X-linked dominant inheritance

18 Y-linked inheritance affects only males always have an affected father
all sons of affected man will be affected no such diseases known, only characteristics such as subfertility and hairy ears

19 Mitochondrial inheritance
mutations in mitochondrial genome maternal inheritance as fathers do not pass mitochondria to their children wide clinical variation due to heteroplasmy (mixture of normal and mutant mitochondria)


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