ANT 1 Lecture Notes - Lecture 4: Mendelian Inheritance, Zygote, Allele Frequency
Document Summary
New cells get same paired chromosomes (like original cell) - diploid. Gametic cells get only 1 of each paired chromosome - haploid. Cross of true-breeding yellow & green parents. Yellow parents produce gametes w/ yellow alleles a. Green parents produce gametes w/ green alleles a. Offspring inherit one gamete from each parent (all aa) A is dominant & a is recessive, so offspring look yellow. Different genotypes can correspond to same phenotype. Each f1 parents produce equal numbers of gametes of each allele. F2 have 50% chance of drawing each allele from each parent. 4 combinations possible: aa, aa, aa, aa. Ratio of genotypes: 1 aa: 2aa: 1aa. Ratio of phenotypes: 3 yellow: 1 green. Punnett square shows why there is a 1:2:1 phenotypic ratio among offspring (f2 generation) Each trait was determined by single gene. Most traits result from many genes acting together. Often there is codominance where heterozygotes have intermediate phenotypes.
