Human Biology: Chromosomes Structure and Functions

Structure of Chromosomes

• Chromosomes are thread-like structures carrying genetic information in the nucleus of eukaryotic cells.
• Each chromosome consists of:
  • Centromere: the region where the chromosome attaches to the spindle fibers during cell division.
  • Telomeres: the protective caps at the ends of chromosomes.
  • Arms: the regions between the centromere and telomeres.

Chromosome Number

• Humans have 46 chromosomes in every cell of their body, except for gametes (sperm and egg cells) which have 23.
• The number of chromosomes varies among species, but is usually consistent within a species.

Chromosome Types

• Autosomes: non-sex chromosomes (1-22 in humans).
• Sex chromosomes: X and Y chromosomes, determining the sex of an individual.
  • XX: female
  • XY: male

Chromosome Functions

• Carry genetic information in the form of DNA.
• Play a crucial role in cell division, ensuring that each new cell receives a complete set of chromosomes.
• Influence the development and growth of an organism.

Chromosomal Abnormalities

• Can occur due to errors during cell division or exposure to mutagenic agents.
• Examples:
  • Aneuploidy: having an abnormal number of chromosomes (e.g., Down syndrome).
  • Chromosomal deletions: loss of a segment of a chromosome.
  • Chromosomal translocations: exchange of genetic material between non-homologous chromosomes.

Chromosomal Mutations

• Can occur due to errors during DNA replication or exposure to mutagenic agents.
• Examples:
  • Point mutations: changes in a single nucleotide.
  • Frameshift mutations: changes in the reading frame of genetic code.
  • Chromosomal inversions: reversal of a segment of a chromosome.