DNA: The Code of Life

Introduction

• DNA is a nucleic acid and a molecule that stores information to control cellular activities, specialization of cells, and arrangement of organs.
• It controls protein synthesis.

Structure of DNA

• DNA stands for Deoxyribonucleic Acid.
• Found in the nucleus of almost every cell.
• Exists as chromatin network (spaghetti-like) and condenses to form chromosomes during cell replication.

Chromosomes

• Humans have 46 chromosomes, 23 from each parent.
• Chromosomes are condensed DNA, wound around proteins.
• Consist of two identical arms (chromatids) joined by a centromere.

Genes

• Short segments of DNA used to create proteins.
• Units of hereditary information inherited from ancestors.

DNA Terminology

• Chromosome: Made of DNA wound around proteins.
• Gene: Segments of DNA coding for proteins.
• Nucleotide: Building block of DNA.
• Nucleus: Cellular location of DNA.

Discovery of DNA

• Discovered by Watson and Crick.
• DNA has a double helix shape.

DNA Structure

• Made up of nucleotides consisting of:
  • Phosphate group
  • Sugar (deoxyribose)
  • Nitrogen base

Nitrogenous Bases

• Four bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
• Complementary base pairs:
  • A pairs with T
  • G pairs with C

DNA Backbone

• Sugar-phosphate backbone holds nucleotides together.
• Weak hydrogen bonds connect complementary bases.

Ring Structures

• Adenine and Guanine have double rings (Purines).
• Thymine and Cytosine have single rings (Pyrimidines).

Function of DNA

1. Hereditary Information:

   • Stored in genes; codes for characteristics like eye color, blood type.

2. Protein Synthesis:

   • DNA provides the code for organisms' growth and development.

3. Replication for Generational Transmission:

   • Essential for passing genetic information to offspring.

Universal Genetic Code

• All organisms have DNA made from A, T, G, and C.
• Differences arise from the order of these bases.
• DNA sequences are millions of letters long, typically addressed in segments.

Summary

• DNA's role in storing genetic information and its ability to replicate are fundamental to life.
• Understanding its structure (double helix) and function (protein synthesis, heredity) is crucial.