Patterns of Inheritance different ways to display Phenotypes

Genes can be inherited based on various patterns Simple Mendelian Dominance vs. Recessive Incomplete dominance Co-dominance Multiple alleles Multiple genes

Homozygous DOMINANT Heterozygous Homozygous recessive Genotype = GG gametes Heterozygous Genotype = Gg G g Gg gametes Homozygous recessive Genotype = bb g gg gametes

Simple Mendelian DOMINANT vs. recessive In this pattern one allele is designated DOMINANT while the other is recessive It only takes the presence of 1 of the dominant allele to determine the dominant phenotype There are only two possible phenotypes (dominant or recessive)

Homozygous condition 1 Homozygous condition 2 Heterozygous Genotype = RR R RR gametes Homozygous condition 2 Genotype = R’R’ R’ R’R’ gametes Heterozygous Genotype = RR’ R R’ RR’ gametes

Incomplete Dominance In this pattern neither allele is considered recessive Heterozygous conditions produce a blend of the two traits creating a third phenotype.

Homozygous condition 1 Homozygous condition 2 Heterozygous Genotype = BB B BB gametes Homozygous condition 2 Genotype = GG G GG gametes Heterozygous Genotype = BG B G RW gametes

Co-dominance In this pattern much like incomplete dominance, neither allele is considered recessive In a heterozygous condition where each type of allele is present the phenotype displays both traits from each allele There are 3 possible phenotypes

Sex Chromosomes – the “X” Genotype = XBXB XB gametes XBXB Genotype = XBXb XB gametes Xb XBXb Genotype = XbXb gametes XbXb Xb

Sex Chromosomes – what about the “Y” Genotype = XBY XB gametes Y XBY Genotype = XbY Xb gametes Y XbY

Sex Linked Genes found on the sex chromosomes X and Y chromosomes are NOT homologous – they DO NOT contain the same genes Males have only one X so the allele they have is their phenotype