Genes and Genetic Diseases

Genes and Genetic Diseases: Comprehensive Study Notes

I. Introduction to Genes and Genetic Diseases

  • Humans possess approximately 20,000 to 25,000 genes.

  • A single error in just one gene can lead to a genetic disease.

  • About 23,000 human genetic traits have been identified to date.

  • Many common diseases have known genetic components, including:

    • Hypertension

    • Coronary heart disease

    • Diabetes

    • Cancer

  • All these conditions are also significantly influenced by environmental factors.

II. The Genetic Code: DNA and its Structure

  • Environmental factors interact with and influence cell function.

  • The nucleus of a cell contains the genetic code essential for all living beings.

  • Chromosomes house genes, which are the fundamental units of inheritance.

  • Genes are composed of sequences of Deoxyribonucleic Acid (DNA).

  • DNA contains the blueprint for proteins, which in turn influence every aspect of body structure and function.

A. Deoxyribonucleic Acid (DNA)

  • DNA is the genetic code.

  • Its structure is famously a double helix.

  • A subunit or nucleotide of DNA is comprised of three components:

    • One pentose sugar (deoxyribose).

    • One phosphate group.

    • One nitrogenous base.

      • Purines: Adenine (A) and Guanine (G).

      • Pyrimidines: Cytosine (C), and Thymine (T).

  • DNA Structure Details (based on visual representation):

    • Helix diameter: 2 nm.

    • Full turn length: 3.4 nm.

    • Distance between base pairs: 0.34 nm.

    • Features include major groove and minor groove.

III. DNA as the Genetic Code for Proteins

  • DNA provides the precise code necessary for synthesizing all body proteins.

  • Proteins are complex molecules made up of one or more polypeptides.

  • Polypeptides are chains of amino acids; there are twenty (20) distinct amino acids.

  • The sequence of three bases, known as a codon, directly dictates the production of a specific amino acid.

  • Termination or nonsense codons signal the stop of protein production.

IV. DNA Replication

  • The process of DNA replication involves:

    • The DNA double helix is untwisted and unzipped, separating into two single strands.

    • Each single strand then serves as a template for the synthesis of a new complementary strand.

    • DNA polymerase enzymes are responsible for pairing the complementary bases:

      • Adenine (A) pairs with Thymine (T).

      • Cytosine (C) pairs with Guanine (G).

    • DNA polymerase also adds new nucleotides and **