Genetics

Key points

This is photograph of chromosome. Seen in the time of cell division

• It contains DNA. DNA is nitrogenous bases containing genetic information

Key points

• Replication: Process of DNA synthesis with each DNA orchestrates the synthesis of daughter DNA
• Transcription: Transfer of Genetic information from DNA to RNA
• Translation: From RNA to Protein

Alleles: Alternative possible genes

• Homozygous: carry two identical alleles
• Hetero: Two different alleles

Incidence: number per 1000 birth

• Prevalence: Proportion affected at a point of time per 1000

Chromasomal ab: 3.2/1000

• Single gene: 7/1000
• Multifactorial polygenic: 30%

Chromasomal

• Structure
  • Deletions
  • Inversions
  • Translocations
• Number
  • Trisomy: Downs
  • monosomy: Turner
  • Addition of extra x: Klinefelter

Single gene

• Variable gene
• Variable penetration
• Variable expressivity
• new gene mutation

Polygenic

• Appreciable gene contribution club foot and DDH
• Familial clustering
• 1st degree relative half proportion genes shared
• Risk of recurrence is square root of population incidence

Risk

• 1st degree relative
• Severe disease
• if rare sex is affected, more risk

AD

• Heterozygous
• M and F affected
• Every generation affected

AR

• Heterozygous no phenotype
• Homozygous expressed
• M and F
• Parents carriers

XR

• Males in every generation affected
• No m to m transmission
• Females are carriers

XD

• M and F
• Males severe