Presentation on theme: "Classification of Genetic Disorders"— Presentation transcript:
1Classification of Genetic Disorders This PowerPoint file contains a number of slides that may be useful for teaching of genetics concepts.You may use these slides and their contents for non-commercial educational purposes.
5Genetic factorsMaleMutations in single genes (often causing loss of function)Variants in genes causing alteration of functionChromosomal imbalance causes alteration in gene dosage
6Classification of genetic disorders Single Gene DisordersMaleMutations in single genesMultifactorial diseases+ environmentVariants in genesChromosome disordersChromosomal imbalance
7Heterozygotes with one copy of the altered gene are affected DominantHeterozygotes with one copy of the altered gene are affectedRecessiveHomozygotes with two copies of the altered gene are affectedMaleX-linked recessiveMales with one copy of the altered gene on the X-chromosome are affected
8Genetic disorders Multifactorial (common) - “Environmental” influences act on a genetic predisposition to produce a liability to a disease.- One organ system affected.- Person affected if liability above a threshold.Single gene (1% liveborn)- Dominant/recessive pedigree patterns (Mendelian inheritance). - Can affect structural proteins, enzymes, receptors, transcription factors.Chromosomal (0.6% liveborn)- Thousands of genes may be involved. - Multiple organ systems affected at multiple stages in gestation. - Usually de novo (trisomies, deletions, duplications) but can be inherited (translocations).
9The contributions of genetic and environmental factors to human diseasesGENETIC ENVIRONMENTALDuchennemuscular dystrophyHaemophiliaOsteogenesis imperfectaClub foot Pyloric stenosis Dislocation of hipPeptic ulcer DiabetesTuberculosisPhenylketonuria GalactosaemiaSpina bifida Ischaemic heart disease Ankylosing spondylitisScurvyRare Genetics simple Unifactorial High recurrence rateCommon Genetics complex Multifactorial Low recurrence rate
10Multifactorial “Environmental” influences act on a genetic predisposition One organ system affected Single gene Dominant/recessive pedigree patterns Structural proteins, enzymes, receptors, transcription factorsChromosomal Multiple organ systems affected Inherited or de novoEnvironmental Drugs, infections
11Single gene disorders High risks to relatives Dominant/recessive pedigree patternsSome isolated cases due to new dominant mutationsStructural proteins, enzymes, receptors, transcription factorsI:1AAI:2ABII:1II:2II:3BB?III:1TomI:1I:2II:1II:2II:3II:5II:6II:8III:1III:2IV:1I:2I:1I:3II:1II:2II:3II:4II:5II:6II:7II:8II:9II:10II:11II:12II:13II:14II:15III:1III:2III:3IV:1IV:2IV:3IV:4III:4III:5IV:5IV:6IV:7III:6III:7IV:8IV:9IV:10III:8III:9III:10III:11III:12III:14III:13III:15III:16III:17IV:11IV:12IV:13