Chromosomes - GCSE Biology Revision Notes

Overview

• Chromosomes are thread-like structures found in the nucleus of eukaryotic cells.
• Made from highly coiled strands of DNA, each chromosome consists of one DNA molecule.

Chromosome Characteristics

• In diploid organisms, chromosomes occur in pairs: one from the mother and one from the father.
• Different species have varying numbers of chromosomes:
  • Humans: 46 chromosomes (23 pairs)
  • Horses: 64 chromosomes (32 pairs)
• Red blood cells lose their nuclei and do not contain chromosomes.

Cell Division and Chromosomes

• Before cell division, genetic material doubles, forming characteristic X-shaped chromosomes.
• Chromosomes are usually uncoiled but condense into recognizable structures when a cell prepares to divide.

Visual Representation

Key Takeaways

• Chromosomes are essential for storing genetic information.
• Proper chromosome duplication is crucial for healthy cell division and organism development.