Medicosis Perfect Status: Genetics Lecture

Introduction

• Topic: Genetics (new sub-series in biology)
• Previous topic: Musculoskeletal system
• Importance of Order: Recommended to watch videos in sequence

Fundamental Concepts

Cellular Organization

• Cells form tissues
• Tissues form organs
• Organs form systems
• Systems perform body functions

Cell Nucleus

• Nucleus: Brain of the cell
• DNA: Contains genetic information
  • Components: Sugar backbone (deoxyribose), phosphate, nitrogenous bases
  • Function: Encodes proteins (enzymes perform body functions)

Chromosomes

• Humans: 46 chromosomes in each somatic cell
• DNA Packaging: DNA wraps around histones to form chromosomes
• Replication: Copying of DNA
• Transcription: DNA to RNA
• Translation: RNA to proteins (enzymes)

Genetic Information

Genes and Alleles

• Gene: Small segment of DNA on a chromosome
• Alleles: Two forms of a gene (one from each parent)
• Locus: Location of a gene on a chromosome
• Dominance: Dominant alleles mask recessive alleles
  • Example: T (tall) vs t (short)
    • TT or Tt: Tall
    • tt: Short
• Homozygous: Two identical alleles (TT or tt)
• Heterozygous: Two different alleles (Tt)

Penetrance vs Expressivity

• Penetrance: Proportion of individuals with a genotype that displays the phenotype
  • Example: 50% penetrance means 50% exhibit the trait
• Expressivity: Degree to which a genotype is expressed in an individual
  • Example: Variable expressivity in neurofibromatosis (no symptoms to severe symptoms)

Blood Group Genetics

Alleles and Blood Types

• Alleles: IA, IB, IO
  • IA and IB are dominant over IO
  • IA and IB show co-dominance
• Possible Genotypes and Phenotypes:
  • OO: Blood type O (no antigens)
  • AA or AO: Blood type A
  • BB or BO: Blood type B
  • AB: Blood type AB (both antigens)

Important Terms

• Genotype: Genetic makeup (not visible)
• Phenotype: Observable traits (manifestation of genotype)

Summary

• Body composed of systems → organs → tissues → cells → nucleus → chromosomes → genes
• Genes have alleles from both parents
• Dominance and recessiveness affect phenotype
• Penetrance and expressivity explain variability in genetic traits
• Blood grouping based on dominance and co-dominance of alleles

Closing

• Resources: Renal physiology and surgery courses available on Medicosis Perfect Status website
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