Genetics

• Genetics is the study of heredity
• Heredity is the passing of traits from parents to offspring
• Gregor Mendel is known as the Father of Modern Genetics
• Mendel used pea plants in his experiments because they grow quickly and produce a large number of offspring
• In Mendel's first experiment, he crossed purebred plants with different traits
• Purebred plants reproduce offspring with the same form of the trait as the parent
• The Parent Generation (P1) involved crossing purebred tall plants with purebred short plants
• The Filial Generation (F1) resulted in all plants being tall
• Mendel let the F1 generation grow and self-pollinate to produce the F2 generation
• In the F2 generation, the offspring were tall and short
• Other traits Mendel studied had the same results, with one trait reappearing in 1/4 of the offspring
• An allele is a form of a gene
• Pea plants inherit a combination of two alleles, one from each parent
• Dominant alleles are expressed over recessive alleles
• Recessive alleles are only expressed when two copies of the gene are inherited
• Purebred or Homozygous genotypes are represented by TT or tt
• Hybrid or Heterozygous genotypes are represented by Tt
• Genotype refers to the combination of alleles for a trait, while phenotype is the physical expression of a trait
• A Punnett Square is used to show all possible outcomes of a genetic cross and determine the probability of a particular outcome
• Incomplete Dominance is a form of inheritance where one allele is dominant over another, resulting in a phenotype that reflects a blending of the two traits
• Codominance is a form of inheritance where both alleles are expressed in the offspring
• Sex-linked traits are controlled by genes located on the sex chromosomes, with color blindness and hemophilia being common examples
• When using a Punnett Square to predict probabilities, the base letters X and Y are used with superscripts denoting the dominant and recessive alleles
• Carriers have one recessive allele and one dominant allele, they do not express the trait but can pass it on to their offspring
• In sex-linkage, the heterozygous genotype is classified as a carrier
• Males are more greatly affected by sex-linked traits
• A pedigree, which looks like a family tree, for any family, be it dogs, cats, plants, or humans, shows the pattern of inheritance in a family for a specfic trait.
• In a pedigre, males are shown as squares and females are shown as circles.
• In a pedigree, each generation is shown as a Roman numeral and each person in a generation is numbered.
• In a pedigree, heterozygous males are shown as half shaded squares and female carriers are shown as half shaded circles.
• In a pedigre, the trait that is being expressed is shown as a shaded trait.