Basic Understanding of Chromosomes

  • Chromosomes are thread-like structures located inside the nucleus of animal and plant cells.
  • Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA).
  • DNA holds instructions, or genes, guiding the functions and characteristics of the cell.

Count of Chromosomes

  • Humans typically have 46 chromosomes in most cells, consisting of 23 pairs.
  • One pair of chromosomes, the sex chromosomes, determines the individual’s sex; XX for females and XY for males.
  • The rest, known as autosomes, are number-coded from 1-22 based on their sizes and shapes.

Role of Chromosomes

  • Chromosomes ensure that DNA is replicated and distributed appropriately during cell division.
  • Each chromosome contains hundreds to thousands of genes that carry information for the production of specific proteins.

Chromosomes and Genetic Variability

  • Genetic variability within a species is due to the combination of genes on the chromosomes received from both parents.
  • Crossing over during meiosis can cause an exchange of different segments of DNA between two homologous chromosomes, leading to genetic variation.
  • Abnormalities in chromosomes, such as missing or extra chromosomes, can lead to genetic disorders.
  • Examples of chromosomal disorders include Down Syndrome (an extra chromosome 21) and Turner Syndrome (missing one sex chromosome in women).