Describe the genetic basis of diseases

Gene Mutations: Small changes in genes can cause diseases, like sickle cell anemia or cystic fibrosis.

Single-Gene Disorders:

Dominant: One bad gene from a parent can cause the disease (e.g., Huntington's disease).

Recessive: You need bad genes from both parents to get the disease (e.g., cystic fibrosis).

X-linked: These are linked to the X chromosome and mostly affect males (e.g., hemophilia).

Complex Diseases: Some diseases are caused by many genes and also by environment (like heart disease and diabetes).

Chromosomal Disorders: Sometimes, having extra or missing chromosomes causes diseases like Down syndrome.

Mitochondrial Diseases: Mutations in the mitochondria (the cell’s power source) can cause diseases passed from mother to child.

Epigenetics: Your environment (like stress or diet) can affect how your genes work, even if the DNA itself isn’t changed.

Gene-Environment Interaction: Some diseases happen because of a mix of your genes and things around you (like asthma triggered by allergens).

Different Causes for the Same Disease: The same disease can have different causes. For example, cystic fibrosis can be caused by many different mutations.

Genetic Testing & Treatment: Doctors can test your genes to see if you’re at risk for certain diseases and give treatments based on your specific genes.

Gene Therapy: Scientists are working on fixing bad genes with gene therapy, which could help cure genetic diseases in the future.

Types of genetic abnormalities
- Point mutation: change in a single base pair
- Frameshift mutation: insertion or deletion of nucleotides that disrupts the reading frame
- Chromosomal mutation: change in the number or structure of chromosomes
- Gene duplication: extra copies of a gene
- Gene deletion: missing copies of a gene
- Gene mutation: change in the DNA sequence of a gene
Genetic basis of Down's syndrome
- Trisomy 21: extra copy of chromosome 21
- Meiosis: process of cell division that produces gametes
- Non-disjunction: failure of homologous chromosomes to separate during meiosis
- Result: 47 chromosomes instead of 46, leading to Down's syndrome
Miasmatic influence on heredity
- Miasma: hypothetical concept of disease-causing agents
- Miasmatic theory: theory that disease is caused by an imbalance of bodily humors
- Influence on heredity: miasma was believed to be inherited through the bloodline

Flowchart of genetic inheritance

      +---------------+
      |  Genetic     |
      |  Information  |
      +---------------+
              |
              |  Mutation
              v

Diagram of meiosis

      +---------------+
      |  Diploid Cell  |
      +---------------+
              |
              |  Meiosis
              v

+---------------+---------------+ | Homologous | Non- | | Chromosomes | Disjunction | +---------------+---------------+ | | Result: 47 v +---------------+ | Trisomy 21 | +---------------+

Anatomical points

Chromosomes are found in the nucleus of eukaryotic cells.
Meiosis occurs in the reproductive cells (gametes).
Non-disjunction occurs during meiosis, resulting in an abnormal number of chromosomes.
Trisomy 21 is a type of chromosomal mutation that leads to Down's syndrome.

GENETIC BASIS DISEASE