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genetics ppt 01
This document discusses various topics in human genetics including: 1. It defines human genetics as the scientific study of human variation and heredity, and medical genetics as the study of the hereditary nature of human disease. 2. Genetic diseases can be caused by inherited mutations, chromosomal abnormalities, or mutations in somatic cells (cancer). Inherited diseases can be due to nuclear or mitochondrial genetic mutations. 3. Examples of inherited genetic disorders and their inheritance patterns are discussed, including autosomal dominant disorders like achondroplasia and autosomal recessive disorders like thalassemia.
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genetics ppt 01
- 1. HUMAN GENETICS Dr. D.A.R.K.Dayarathna MD (medicine –col), MSc (medical genetics –Ncl - UK)
- 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. Causes of diseases • Accidents • Infections • Genetic diseases • Complex traits
- 4. Genetic diseases • Inheriteddiseases • Diseases due to mutations in somatic cells- cancer
- 5. Inherited diseases • Dueto genetic mutations- nuclear, Mitochondrial • Chromosomal abnormalities • Complex traits, multifactorial disorders
- 6. Mutations • Deletions- rangingfrom 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. Mutation- functional change •Loss of function mutations • Gain of function mutations
- 8. Loss of function •Autosomal recessive disorders
- 10. Autosomal dominant • Dominantnegative • Haplo insufficiency
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- 15. Gene structure andprotein synthesis
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- 20. Down syndrome • Commoncause 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
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- 24. 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
- 25. 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
- 26. Autosomal dominant ctd •Codominance- when both traits are expressed fully in heterozygous state. Ex- AB blood group • Intermediate inheritance • Ex- sickle cell trait
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- 29. 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
- 30. 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
- 31. Neurofibramatosis •Skin fibromas •Neuro fibromas •Capu lau spot •Variable clinical manifestation
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- 33. Hypertropic obstructive cardiomyopathy • Presentation Sudden death Chest pain on excretion palpitation
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- 37. 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
- 39. 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
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- 45. X linked recessiveinheritance • 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
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- 49. 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
- 50. Lyon hypothesis • Random inactivation of one X chromosome in early foetal development
- 52. X linked dominantinheritance • Affect either sex but more female then males • Female are often more mildly and more variably then males • No male to male transmission
- 54. Mitochondrial inheritance • Matrinealinheritance • Variable clinical manifestation due to heteroplasmy
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- 58. 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
- 59. E/M view ofdiseased mitochondria
- 60. Mitochondrial myopathies • Kern sayare syndrome • Chronic progressive external opthalmoplegia
- 61. Complex traits Diabetes mellitus,Hypertension, mental disorders etc
- 62. Complex traits ctd • Gene and environment interaction • Population studies • Family studies • Twin studies