1. Alternative versions of genes lead to variations in inherited characters. Alternative versions are called alleles 2. Each individual receives 2 alleles. –homozygotes: 2 copies of identical allele –heterozygotes: two different alleles Mendels model
3. In heterozygotes only the dominant form of allele will be expressed. –genotype: alleles present –phenotype: physical appearance 4. Alleles segregate from one another into gametes (Law of segregation) Mendels model
Allele for purple flowers Homologous pair of chromosomes Allele for white flowers Locus for flower-color gene Chromosomes, genes and alleles ……..
Dominant phenotype, unknown genotype: PP or Pp? If PP, then all offspring purple: pp P P Pp If Pp, then 1 2 offspring purple and 1 2 offspring white: pp P P pp Pp Recessive phenotype, known genotype: pp The testcross