1. Patterns of Inheritance
different ways to display Phenotypes

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

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

4. 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)

5. 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

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

7. 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

8. 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

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

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

11. 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