LIFE 120 Lecture Notes - Lecture 11: Dihybrid Cross, Punnett Square, F1 Hybrid
Document Summary
Co(cid:373)peti(cid:374)g h(cid:455)potheses i(cid:374) (cid:1005)8(cid:1004)(cid:1004)"s: how are genetic traits passed from parents to offspring, the (cid:862)(cid:271)le(cid:374)di(cid:374)g(cid:863) h(cid:455)pothesis. Problem leads to (cid:862)ge(cid:374)eti(cid:272)(cid:863) u(cid:374)ifor(cid:373)it(cid:455): me(cid:374)del & (cid:862)parti(cid:272)ulate(cid:863) h(cid:455)pothesis. Pea varieties with distinct heritable traits (flower & seed color) Controlled mating: manipulated flowers, cross-pollinate, hybridization, ele(cid:272)ted (cid:862)true-breeding(cid:863) pla(cid:374)ts. Gene- sequence of dna encoding a protein. Egg/sperm get only one of two alleles. Segregation of alleles results when homologous chromosomes go to different gametes in meiosis. Parent genotype: pp purple parent, pp white parent. Gamete genotype: p purple gamete, p white gamete. Homozygous alleles same at both loci. Phenotype - appearance of the organism, observed trait purple or white. Genotype & phenotype same in p generation. F1 generation = hybrids: monohybrid cross. Genotype: pp all hybrid, heterozygous. Phenotype: all purple, p is dominant. Hybrids produce 2 type gametes p & p. Genotype punnett square: predicts offspring allele composition due to random fertilization, 1 pp: 2pp: 1 pp. Phenotype observed offspring traits: 3 purple: 1 white.
