Lecture Notes: Genes, DNA, and Chromosomes

Introduction

• Genes, DNA, and chromosomes are the fundamental components that determine individual characteristics.
• These components form the set of instructions inherited from both parents.
• Present in every cell of living organisms.

Cell Structure

• Types of Cells: Includes nerve cells, hair cells, skin cells, etc.
• Basic Parts of a Cell:
  • Cell Membrane: Acts as the outer border.
  • Cytoplasm: Liquid material inside the membrane.
  • Nucleus: Located within the cytoplasm containing chromosomes.

Chromosomes

• Humans have 23 pairs of chromosomes, totaling 46.
• Autosomes: 22 pairs common to both males and females.
• Sex Chromosomes: 23rd pair differs between genders.
  • Females: Two X chromosomes.
  • Males: One X and one Y chromosome.

DNA (Deoxyribonucleic Acid)

• Chromosomes consist of long strings of DNA.
• Structure: Double helix, resembling a twisted ladder.
• Bases:
  • Adenine (A), Thymine (T), Guanine (G), Cytosine (C).

Genes

• A stretch of DNA that acts like a recipe for building proteins.
• DNA Sequence: Order and length of bases determine protein characteristics.
• Protein Function:
  • Proteins determine cellular structure and function.
  • Cells form tissues, tissues form organs (e.g., eyes, skin).

Role of Genes in Determining Characteristics

• Genes dictate species (e.g., human, cow, apple) and physical appearance (e.g., hair color, skin color, eye color).

Summary

• Genes, DNA, and chromosomes are crucial in defining the biological and physical traits of all organisms.
• Understanding these components elucidates how genetic information is transferred and expressed.