Genetics

Key Concepts in Genetics

  • Genome:

    • Definition: Entire genetic material of an organism.

  • Chromosomes:

    • Structures occurring in functional pairs in the nucleus of cells (except in gametes and bacteria).

  • Genes and Alleles:

    • Genes: Sections of chromosomes made of DNA that control characteristics.
    • Alleles: Different forms of the same gene.

  • DNA Structure:

    • Composed of a phosphate and deoxyribose sugar backbone.
    • Four bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
    • Base pairing rules: A pairs with T, C pairs with G.
    • Forms a double helix.
    • Each unit (nucleotide) consists of a sugar, phosphate, and base.

Mitosis and Meiosis

  • Mitosis:

    • Type of cell division resulting in genetically identical daughter cells (clones).
    • Crucial for growth, cell replacement, and tissue repair.

  • Meiosis:

    • Type of cell division resulting in four genetically diverse haploid cells (gametes).
    • Important for sexual reproduction.
    • Involves independent assortment, leading to genetic variation.

Genetic Diagrams and Crosses

  • Monohybrid Cross:

    • Focuses on a single characteristic controlled by one gene with two alleles (e.g., Tt).
    • Involves understanding genotype (allele combinations), phenotype (observable traits), and ratios of offspring.

  • Test Cross:

    • Used to determine an unknown genotype by crossing with a homozygous recessive individual.

Genetic Conditions

  • Haemophilia:

    • Sex-linked disorder affecting blood clotting, generally in males.

  • Cystic Fibrosis:

    • Autosomal recessive disorder leading to frequent lung infections and digestive issues.

  • Huntington's Disease:

    • Autosomal dominant condition causing progressive brain deterioration, onset usually in middle age.

  • Down's Syndrome:

    • Chromosomal condition caused by an extra chromosome (usually resulting in 47 chromosomes).

Genetic Screening and Ethical Issues

  • Genetic Screening:

    • Process for testing the presence of harmful alleles or genetic abnormalities via methods like amniocentesis or blood tests.
    • Ethical considerations include privacy, potential discrimination, and the consequences of choosing to terminate pregnancies based on results.

  • Abortion Considerations:

    • Ethical debates surrounding the termination of pregnancies when a genetic condition is diagnosed.

Genetic Engineering

  • Genetic Engineering:

    • The process of modifying an organism's genome to introduce desirable traits.
    • Example: Inserting a human insulin gene into bacteria to produce insulin.
    • Involves using restriction enzymes to join DNA segments, allowing bacteria to reproduce and manufacture human insulin.

  • Downstreaming Process:

    • Includes extracting, purifying, and packaging the insulin produced by genetically modified organisms.
    • Advantages include avoiding animal disease transmission and optimizing insulin production efficiently.