genetics

Cards (12)

  • Aims of Medical Genetics
    • Understand the genetic basis and molecular pathology of inherited disease
    • Laboratory diagnostic services
    • Provide risk calculation, diagnosis & counselling, etc
    • Work towards a cure / better management for inherited diseases
  • Genes and chromosomes
    • Chr 1: ~2,047 protein-coding genes
    • Chr 21: ~231 protein-coding genes
    • Each chromosome is a long double-stranded DNA molecule, coated with proteins
    • DNA = deoxyribonucleic acid
  • Patterns of Inheritance
    • Chromosomal
    • Single gene disorder: Autosomal dominant, Autosomal recessive, X-linked recessive, (X-linked dominant)
    • Multiple genes + environmental factors (multifactorial)
    Multiple genes +/- chromosomal abnormalities​
    (cumulative genetic)​
    Extra chromosome 18- Edwards syndrome​
    Mendelian- single gene disorder​
  • Variable expressivity - People affected at different extends by same disorder​
  • Dominant or recessive inheritance?
    • Dominant - only need one faulty gene to get disease
    • Often: "Variable expressivity"
  • Dominant or recessive inheritance?
    • Features: Vertical or Horizontal Pattern
    • Horizontal: People in single generation affected
    1. linked or autosomal inheritance?
    • Features: Male to male transmission
    • Mode of inheritance: Autosomal (because a man passes on Y (not his X) chromosome to sons)
  • Knight's move inheritance
    • Features: Two males related through unaffected female
    • Only males affected
    • Mode of inheritance: X-linked recessive (the female has an additional unaffected X chromosome which 'protects' her)
  • Effects of genetic variants
    • Complete inactivation of function (e.g. deletions; premature translation stop)
    • Decreased function (e.g. amino acid substitutions in key regions, regulatory variants)
    • No significant effect (e.g. non-coding DNA, no change in amino acid, alters less important region of protein)
    • Increased or changed function (e.g. amino acid substitutions in key regions, regulatory variants, duplications)
  • Variants & inherited disease
    • Disease or condition can occur in all people with a particular variant in 1 gene copy (e.g. achondroplasiadominant mutation)
    • Some variants may cause disease only when both copies of the same gene are affected (e.g. cystic fibrosis - recessive)
  • Cystic fibrosis
    • Affects children and young adults
    • Affects digestion and respiratory system
    • Affects males and females
    • Horizontal pattern
    • Autosomal recessive inheritance
  • Normal way gene switched on ​
    RNA polymerase carries out mRNA ​
    Protein made in ribosomes​
    Chain of amino acids - polypeptide​
    Gene- made of exons and introns, exons kept and introns removed​
    Always start with methionine - start codon ​