Pathophysiology 1 - Lecture on Genetic Diseases

Overview of Genetic Diseases

• Focus on:
  • Mutations
  • Chromosomal Aberrations or Alterations
  • Transmission of Genetic Diseases

DNA Basics

DNA Replication

• DNA unwinds and unzips for replication during the S phase of interphase.
• Complementary base pairing: Cytosine-Guanine, Adenine-Thymine.
• DNA polymerase assists in replication.

Transcription and Translation

• Purpose: DNA carries genetic information for protein synthesis.
• Transcription: DNA segment (gene) is copied into mRNA.
  • mRNA contains Uracil instead of Thymine.
  • mRNA leaves nucleus to ribosome.
• Translation: mRNA to Protein
  • Codons: Set of three nucleotides on mRNA.
  • tRNA brings amino acids matched to codons, forming polypeptides/proteins.

Mutations

Definitions

• Mutation: Change in gene sequence (inherited or not).
• Mutagen: Agent that increases frequency of mutations.
  • Types: Physical (e.g., radiation), Chemical (e.g., formaldehyde), Biological (e.g., viruses).
• Mutations can be silent, sublethal, or lethal.

Types of Mutations

• Base Pair Substitutions:
  • My Sense Mutation: One pair substituted, causing amino acid change.
  • Nonsense Mutation: Substitution creates stop codon, halting protein synthesis.
• Frame Shift Mutations:
  • Insertions or deletions causing shifts in reading frame, altering downstream amino acids.

Chromosomal Aberrations

Numerical Abnormalities

• Polyploidy: More than normal chromosome number (e.g., triploidy, tetraploidy).
• Aneuploidy: Abnormal number of a single chromosome (e.g., monosomy, trisomy).
• Monosomy: Loss of one chromosome can be lethal.
• Trisomy: Extra chromosome (e.g., Down syndrome - Trisomy 21).

Structural Abnormalities

• Deletions: Loss of chromosome part.
• Duplications: Gain of chromosome part.
• Inversions: Two breaks, segment inserted in reverse order.
• Translocations: Exchange of segments between non-homologous chromosomes.

Genetic Testing

• Prenatal Diagnosis: Amniocentesis and Chorionic Villus Sampling (CVS) for detecting abnormalities.
  • Risks involved, used for high-risk pregnancies.

Transmission of Genetic Diseases

Key Definitions

• Genetically Inherited: Passed from parents to offspring.
• Congenital: Present at birth, not always inherited.
• Acquired in Utero: Environmental factors during pregnancy causing malformations.

Inheritance Patterns

• Autosomal: Affect chromosomes 1-22.
• Sex-linked: Affect chromosomes X or Y.
• Recessive: Requires two copies for expression.
• Dominant: One copy can express the trait.

Examples

• Retinoblastoma: Dominant, autosomal.
• Cystic Fibrosis: Recessive, autosomal.

Multifactorial Inheritance

• Caused by combination of genetic, environmental, and lifestyle factors.
• Examples include cancer, heart disease, diabetes, and congenital malformations.

---

• Visit specified resources for further exploration of genetic analysis and art.