Genetic Traits Genotype: The types of the genes of an organism Phenotype: The observable characteristics of an organism Gametes: Haploid sex cells created for sexual reproduction Zygote: Diploid cell created by the fusion of sperm and egg Genetic Traits and Vocab Dominant Gene: A gene that can be expressed in the homozygous (2 copies) or heterozygous condition (1 copy of each). Recessive Gene: A gene that is only expressed in the homozygous (two copies) condition. This gene can be masked by the dominant gene. Allele: Version of a gene (may be dominant or recessive) Homozygous: The state of having two identical alleles of a particular gene (eg AA, aa). Hybrid/Heterozygous: The state of having two different alleles of a particular gene (eg Aa) Mendelian Genetics: Gregor Johann Mendel (1822-1884) Augustinian monk, Czech Republic. Foundation of modern genetics. Studied segregation of traits in the garden pea (Pisum sativum) beginning in 1854. Published his theory of inheritance in 1865. Mendel was “rediscovered” in 1902. Some basic terminology: Generations: P = parental generation F1 = 1st filial generation, progeny (offspring) of the P generation F2 = 2nd filial generation, progeny of the F1 generation (F3 and so on) Crosses: Monohybrid cross = cross of two different true-breeding strains (homozygotes) that differ in a single trait. *Genetics etiquette - female conventionally is written first Simple Dominance Examples: Fig. 10.4, Mendel’s 7 garden pea characters. (W)Widows Peak vs. Straight (w) (E)Wet ear wax vs. Dry ear wax (e) (F)Free Earlobe vs. Attached (f) Six-digits (F) Cleft chin (C) Tongue Roll (T) Hitchhiker’s Thumb (H) Hand and Arm Crossing Left hand clasped over right is dominant Right arm folded over left is dominant PTC People who have the ability to taste PTC are dominant to people who cannot What is the benefit for having certain taste? About 40 percent of people cannot taste/smell cyanide.