Understanding the basic principles of genetics, including the structure and function of DNA, genes, alleles, and chromosomes.
Introduction to Genetics – Study Notes
| Year | Scientist | Contribution |
|---|---|---|
| 1859 | Charles Darwin | Theory of natural selection (variation & inheritance) |
| 1865 | Gregor Mendel | Laws of inheritance from pea‑plant experiments |
| 1902 | Walter Sutton & Theodor Boveri | Chromosome theory of inheritance |
| 1953 | James Watson & Francis Crick | DNA double‑helix structure |
| 1970s | Frederick Sanger | DNA sequencing methods |
| 1980s‑1990s | Human Genome Project | Mapping the entire human genome |
| Term | Meaning |
|---|---|
| Gene | Segment of DNA that codes for a functional product (protein or RNA) |
| Allele | Alternative form of a gene (e.g., A vs. a) |
| Locus | Physical location of a gene on a chromosome |
| Genotype | Genetic makeup of an individual (e.g., AA, Aa, aa) |
| Phenotype | Observable traits resulting from genotype + environment |
| Dominant | Allele that masks the effect of a recessive allele in heterozygotes |
| Recessive | Allele whose effect is seen only when two copies are present |
| Homozygous | Same alleles at a locus (AA or aa) |
| Heterozygous | Different alleles at a locus (Aa) |
| Polygenic | Trait controlled by many genes (e.g., height) |
| Epistasis | Interaction where one gene masks the effect of another |
Typical Monohybrid Cross (single trait)
| Parental Genotypes | Gametes | F1 Generation | F2 Generation Ratio (Genotype) |
|---|---|---|---|
| AA × aa | A, a | All Aa (heterozygous) | 1 AA : 2 Aa : 1 aa |
| (uniform phenotype) | 3 dominant : 1 recessive |
Dihybrid Cross (two traits) – 9:3:3:1 phenotypic ratio when genes assort independently.
| Pattern | Description | Example | |---------|-------------