genetics ppt 01

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DARK. Dayaratna (consultant physician, MSc in genetics)

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genetics ppt 01

  1. 1. HUMAN GENETICSDr. D.A.R.K. DayarathnaMD (medicine –col),MSc (medical genetics –Ncl - UK)
  2. 2. Genetics• Human genetics- scientific study of human variation and Heredity• Medical genetics - study of the hereditary nature of human disease• Clinical genetics- Care, diagnosis and counseling of patients with congenital malformations or genetic diseases
  3. 3. Causes of diseases• Accidents• Infections• Genetic diseases• Complex traits
  4. 4. Genetic diseases• Inherited diseases• Diseases due to mutations in somatic cells- cancer
  5. 5. Inherited diseases• Due to genetic mutations- nuclear, Mitochondrial• Chromosomal abnormalities• Complex traits, multifactorial disorders
  6. 6. Mutations• Deletions- ranging from 1 bp to mega base• Insertions- including duplications• Single base substitution-• Missense mutations- replace one amino acid with another in the gene product• Nonsense mutations replace one amino acid codon with a stop codon• Splice site mutations create or destroy signals for exon/intron splicing• Frame shifts can be produced by
  7. 7. Mutation- functional change• Loss of function mutations• Gain of function mutations
  8. 8. Loss of function• Autosomal recessive disorders
  9. 9. Autosomal dominant• Dominant negative• Haplo insufficiency
  10. 10. Dominant negative mutation
  11. 11. Karyotype
  12. 12. Gene structure and protein synthesis
  13. 13. GENE expression
  14. 14. Down syndrome
  15. 15. Down syndrome• Common cause for • Screening – triple test mental retardation - alpha feto• Most are due to protien trisomy -oestriol 21,nodisjunction - chorionic• Elderly mothers are gonadotopihic more suseptible hormone• 2-3% due to - ultra sound translocatin of 21to14 scan -amniocentesis
  16. 16. Turner syndrome
  17. 17. Klinefelter syndrome
  18. 18. Fragile X syndrome
  19. 19. Fragile X syndrome • Inherited cause of intellectual disability • Large protruding ears,large testiclesle • Due to mutation of the fragile X mentel retardation 1 ( FMRI) • X linked dominent condition with variable expressivity
  20. 20. Autosomal dominant inheritance• Males and females are equally affected• Transmission between all sexes are observed . Male to male, female to male• Symptoms usually appear later in life• Pleiotrophy- single gene disorder produce multiple phenotypic effect• Variable expressivity of gene• Reduced or incomplete penetrance, the
  21. 21. Autosomal dominant ctd• Codominance- when both traits are expressed fully in heterozygous state. Ex- AB blood group• Intermediate inheritance• Ex- sickle cell trait
  22. 22. Pedigree symbols
  23. 23. Achondroplasia •Common genetic cause of dwarfism •Mutation in the fibroblast growth factor receptor 3(FGFR3) •Cause abnormality of cartilage formation •Can be detected before birth by prenatal ultrasound
  24. 24. Autosomal dominant polycystic kidney disease •Inherited systemic disease • 1 in 400 to 1 in 1000 •Mutation in PKD1 and PKD 2 gene •Cyst in liver, pancreas, cerebral aneurysm, mitral valve prolapse. •Imaging and molecular studies
  25. 25. Neurofibramatosis •Skin fibromas •Neuro fibromas •Capu lau spot •Variable clinical manifestation
  26. 26. Hereditary spherocytosis
  27. 27. Hypertropic obstructive cardiomyopathy • Presentation Sudden death Chest pain on excretion palpitation
  28. 28. Mafan syndrome
  29. 29. Osteogenesis imperfecta
  30. 30. Familial hypercholesterolemia
  31. 31. Brugada Syndrome • More in asia • Cause of sudden death in young • Can present with atypical chest pain and recurrent palpitation • Mutation in sodium ion channels • Cause of death is VF • Implantable cardioverter defibrillator
  32. 32. Autosomal recessive inheritance• Presentation - in early age, usually with severe symptoms• Affect either sex• Affected people are usually born to unaffected parents• Parents are usually asymptomatic carriers• Increase incidence of parental consanguinity• After the birth of an effected child, each subsequent child has a 25% of being Affected
  33. 33. Autosomal recessecive pedigree
  34. 34. Thalasaemia
  35. 35. Albinism
  36. 36. White Tiger
  37. 37. X linked recessive inheritance• Affect mainly males• Affected males are usually born to un affected parents• Mother is normally an asymptomatic carrier• There is no male to male transmission in the pedigree
  38. 38. Color blindness(X-linked)
  39. 39. Duchenne muscular dystrophy • Common inherited muscular dystrophy • Mutation in dystrophin gene • Symptoms before age of 05 • Progressive muscle weakness • Pseudo hypertrophy of calf muscles • Cardiac involvement
  40. 40. Lyon hypothesis • Random inactivation of one X chromosome in early foetal development
  41. 41. X linked dominant inheritance• Affect either sex but more female then males• Female are often more mildly and more variably then males• No male to male transmission
  42. 42. Mitochondrial inheritance• Matrineal inheritance• Variable clinical manifestation due to heteroplasmy
  43. 43. Mitochondrial inheritance ctd
  44. 44. Mitochondrial disease • Ragged Red Fibers" - clumps of diseased mitochondria accumulate in the subsarcolemmal region of the muscle fiber and appear as "Ragged Red Fibers" when muscle is stained with modified Gömöri trichrome stain
  45. 45. E/M view of diseased mitochondria
  46. 46. Mitochondrial myopathies • Kern sayare syndrome • Chronic progressive external opthalmoplegia
  47. 47. Complex traitsDiabetes mellitus, Hypertension, mental disorders etc
  48. 48. Complex traits ctd• Gene and environment interaction• Population studies• Family studies• Twin studies

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