Lecture Notes: Genes, DNA, and Chromosomes

Overview

• Genes, DNA, and chromosomes are fundamental to determining individual identity.
• These elements act as instructions inherited from parents.
• Present in all cells, these components are essential to life.

Cells

• All living organisms are composed of cells.
• Different types of cells include:
  • Nerve cells
  • Hair cells
  • Skin cells
• Basic cell structure:
  • Membrane: The outer border of the cell.
  • Cytoplasm: Liquid material within the cell.
  • Nucleus: Contains chromosomes.

Chromosomes

• Humans typically have 23 pairs of chromosomes (46 total) in each cell.
  • 22 pairs are autosomes, appearing the same in both males and females.
  • 1 pair is the sex chromosomes:
    • Females: XX
    • Males: XY

DNA (Deoxyribonucleic Acid)

• Long strings forming the chromosomes.
• Structure:
  • Double helix: Ladder-like shape that is twisted.
  • Composed of four bases:
    • Adenine (A)
    • Thymine (T)
    • Guanine (G)
    • Cytosine (C)

Genes

• A segment of DNA is known as a gene.
• Genes function like a recipe for building proteins.
• Protein Synthesis:
  • Order, length, and sequence of DNA bases determine the protein's size and shape.
  • Protein size and shape dictate its function in the body.

Biological Hierarchy

• Proteins form cells.
• Cells form tissues.
• Tissues form organs (e.g., eyes, skin).

Determinants of Physical Traits

• Genes influence:
  • Species identity (e.g., human, cow, apple).
  • Physical attributes:
    • Hair color
    • Skin color
    • Eye color

Conclusion

• Genes, DNA, and chromosomes are crucial for defining not only our species but also individual physical characteristics.