Genetics

Genetics is the branch of biology that studies genes, heredity, and variation in living organisms. It explains how traits (such as eye color, height, or disease risk) are passed from parents to offspring through DNA.

Genetics plays a crucial role in health, evolution, and biological diversity, influencing everything from physical characteristics to the likelihood of developing certain diseases.

Key Concepts in Genetics

1. Genes & DNA

  • Genes are segments of DNA (deoxyribonucleic acid) that contain instructions for making proteins.
  • DNA is made of four nucleotide bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
  • These bases pair in a double-helix structure: A pairs with T, and C pairs with G.

2. Chromosomes

  • Chromosomes are long strands of DNA wrapped around proteins.
  • Humans have 46 chromosomes (23 pairs)—one set inherited from each parent.
  • The 23rd pair determines biological sex: XX (female) or XY (male).

3. Inheritance & Heredity

  • Heredity is the passing of genetic traits from parents to offspring.
  • Genes come in different versions (alleles), determining unique traits.
  • Dominant alleles (e.g., brown eyes) override recessive alleles (e.g., blue eyes).
  • Some traits are controlled by a single gene (Mendelian traits), while others involve multiple genes (polygenic traits).

4. Genetic Variation & Mutations

  • Genetic variation allows differences among individuals in a species.
  • Mutations are changes in DNA sequences that may lead to new traits, diseases, or evolutionary adaptations.

5. Genotype vs. Phenotype

  • Genotype = The genetic code of an organism (DNA sequence).
  • Phenotype = The physical expression of genes (eye color, height, etc.).

Types of Genetic Inheritance

  1. Mendelian (Single-Gene) Inheritance
    • Traits follow predictable patterns (e.g., dominant vs. recessive genes).
    • Example: Cystic fibrosis, sickle cell anemia.
  2. Polygenic Inheritance
    • Traits controlled by multiple genes.
    • Example: Height, skin color, intelligence.
  3. Sex-Linked Inheritance
    • Genes located on X or Y chromosomes.
    • Example: Color blindness, hemophilia (X-linked traits).

Applications of Genetics

✅ Medicine & Genetic Disorders – Identifying genetic risks for diseases like cancer or diabetes.
✅ Forensics & DNA Fingerprinting – Solving crimes using DNA evidence.
✅ Genetic Engineering & CRISPR – Editing genes to cure diseases or modify traits.
✅ Ancestry & Evolution – Understanding family history and human origins.

Conclusion

Genetics is the study of how traits are inherited and expressed. It explains why individuals look different, have unique abilities, or inherit diseases. Advances in genetics continue to revolutionize medicine, biology, and biotechnology.