Introduction to DNA: The Code of Life

Overview

• DNA is a nucleic acid responsible for storing necessary information to control cellular activity.
• It is involved in cell specialization, tissue organization, and protein synthesis.

Structure and Location

• Deoxyribonucleic Acid (DNA): Structure of the molecule gives its name.
• Location: Found in almost every cell, primarily in the cell nucleus.
  • Found as chromatin network in nucleus, condenses into chromosomes for replication.
  • Humans have 46 chromosomes (23 from each parent).

Chromosomes

• Composed of DNA wound around proteins, forming a chromatin network when not replicated.
• Chromosomes become visible and condensed during cell division.
• Consist of two identical chromatids joined by a centromere.

Genes

• Genes are segments of DNA coding for proteins and are hereditary information units.
• Found on chromosomes and responsible for inherited traits.

DNA Structure

• Double Helix: Discovered by Watson and Crick. DNA is in a spiral shape with a ladder-like structure.
• Nucleotides: Building blocks of DNA, consisting of:
  • Phosphate group
  • Sugar (deoxyribose)
  • Nitrogenous base

Nitrogenous Bases

• Four types: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
• Base pairing: A pairs with T, G pairs with C.
• Base pairs are held together by weak hydrogen bonds.

DNA Backbone

• Made up of sugar-phosphate backbone running down each side.
• Essential for the structure of DNA strands.

Nitrogenous Base Structures

• Purines: Double ring structures (Adenine and Guanine).
• Pyrimidines: Single ring structures (Thymine and Cytosine).

DNA Function

• Hereditary Information: Carries genes that code for characteristics like eye color, blood group, and muscle growth.
• Protein Synthesis: Provides blueprint for organism growth and development.
• Replication: Allows DNA to be passed to the next generation through cell division.

Important Concepts

• DNA Code: Composed of sequences of A, T, G, and C. Order determines protein and organism characteristics.
• Genetic Code Uniformity: Same four letters used across all organisms, differing only in sequence order.