“Chromosomes: The Blueprint of Life”

Chromosomes – The Carriers of Heredity Introduction Chromosomes are thread-like structures found in the nucleus of all living cells. They are made of DNA and proteins and act as carriers of genetic information from one generation to the next. Each chromosome contains many genes, which are the functional units of heredity. ⸻ Structure of Chromosomes 1. Chromatid – Each chromosome consists of two identical sister chromatids joined at the centromere. 2. Centromere – Constriction point that holds the chromatids together; it helps in movement during cell division. 3. Telomere – Protective ends of chromosomes that prevent damage and fusion with other chromosomes. 4. Chromatin – DNA exists in a less condensed form (chromatin) during interphase and condenses into visible chromosomes during cell division. 5. DNA & Histones – DNA is wrapped around histone proteins, forming nucleosomes, which further fold to make the chromosome compact. ⸻ Types of Chromosomes • Autosomes – Non-sex chromosomes (in humans, 22 pairs). • Sex chromosomes – Determine the sex of an individual (XX in females, XY in males). • Based on centromere position: • Metacentric – centromere in the middle. • Submetacentric – centromere slightly off-center. • Acrocentric – centromere near one end. • Telocentric – centromere at the very end. ⸻ Functions of Chromosomes 1. Genetic information storage – Carry genes that control traits and functions. 2. Transmission of heredity – Ensure transfer of genetic material from parents to offspring. 3. Control of cell division – Help in proper segregation of DNA during mitosis and meiosis. 4. Regulation of gene expression – Influence when and how genes are turned on or off. 5. Maintenance of genome stability – Telomeres and centromeres protect integrity of DNA. ⸻ Human Chromosome Number • Humans have 46 chromosomes (23 pairs). • 22 pairs are autosomes. • 1 pair is sex chromosomes.