Transmission Genetics and Mendelian Principles

Study Notes

Transmission genetics is the study of how traits are passed from parents to offspring.
Early theories proposed that traits were passed from different parts of parents to offspring by concentrating these traits into the gamete, then to the progeny.
Weismann distinguished between germplasm (reproductive cells) and somatoplasm (other body cells). He proposed that inherited traits are transmitted through germplasm, unaffected by somatic cell changes.
This theory supported Mendel's laws.

Images of pea plants and Mendel were presented.
A table showed various traits like seed form, cotyledon color, pod form, pod color, stem place, and stem size.

A trait's disappearance after a generation led to gene representations. Dominant genes express their trait regardless of the other gene. Recessive genes express their trait only if there are two identical recessive genes.
Mendel used symbols to represent genes (e.g., P = purple flower, p = white flower, capital letters for dominant, lowercase for recessive).

First-generation (F1) plant generation was all purple.
Second-generation (F2) plants showed a 3:1 ratio between purple and white flowers (purple dominant).
Diagrams illustrated homozygous and heterozygous crosses.

First Law (Law of Segregation): During gamete formation, alleles separate from each other. Each gamete receives only one allele from the pair.
- Example given of a cross between a tall plant (TT) and a dwarf plant (tt).
- F2 Genotypic ratio: 1:2:1
- F2 Phenotypic ratio: 3:1
Monohybrid Cross: genetic cross involving one trait.
Monohybrid Ratio: Ratio produced from a monohybrid cross.
Test Cross: Use to determine if a plant with a dominant phenotype was homozygous or heterozygous.
Individuals with a dominant phenotype and who are unsure of their genotype are crossed with a known homozygous recessive individual to determine the genotype of the unknown parent.