Transcript file
Basic Genetics The Father of Genetics Gregor Mendel – Austrian monk – – – Carried out the first studies of heredity Successfully predicted how traits would be passed Studied the garden pea plant Basic terminology Heredity – passing of characteristics from parents to offspring Gametes –male and female sex cells Fertilization – process where male and female sex cells unite – Produces a zygote (fertilized egg) Cross – pollination Mendel used to fertilize pea plants He would take pollen from one plant and dust on another Rule of unit factors Mendel concluded that two factors control each trait Each factor is called an allele – An allele is the different forms of a gene Examples: blue, green, brown are different alleles for the eye color gene Rule of dominance One allele is usually seen more often than the other – – – Dominant alleles are observed more often Recessive alleles disappear To write alleles we abbreviate: Capitol letter for the dominant Lower case letter for the recessive – Always use the first letter of the dominant allele for both the dominant and the recessive alleles Genotype vs. Phenotype Phenotype: the physical appearance – – Can be determined by looking at the organism Tall, short, blue eyes, brown hair Genotype: the allele combination – – – Cannot be determined by looking at the organism Can be homozygous (TT, tt, AA, aa) Can be heterozygous (Tt, Aa) Law of segregation Every individual has 2 alleles of each gene and when gametes are produced, each gamete receives one of these alleles During fertilization, gametes randomly pair to produce 4 combinations Punnett squares Shorthand way of finding possible genotypes of the offspring Monohybrid cross – 4 boxes in square Dihybrid cross – 16 boxes Punnett squares Parental gametes go along the top and down the side Inside the boxes, the possible combinations of the offspring Dihybrid crosses Involves two traits Follows the law of independent assortment – Genes for different traits are inherited independently of each other Dihybrid Punnett squares Must use all possible combinations of alleles when setting up the Punnett square AATt x Aatt – – Must use the foil method to place gametes along the top and side Combine as usual for the combinations in the offspring Genotypic and phenotypic ratios Once Punnett square is complete, you must calculate the genotypic ratios and the phenotypic ratios