Alternative Types of Inheritance DominantRecessive Inheritance where there

Alternative Types of Inheritance

Dominant/Recessive • Inheritance where there are 2 alleles one of which prevails over the other – No mixing – No in between • Ear lobes- recessive means attached ear lobes, if have dominant gene show detached ear lobes -Attached ear lobe - Genotype: ee -Detached ear lobes - Genotype: Ee or EE

Incomplete Dominance • Phenotype of a heterozygous individual is intermediate between those of two homozygous individuals • Ex. Snap Dragon Plant Red snap dragon plant Pink snap dragon plant White snap dragon plant Genotype: RR Genotype: Rr Genotype: rr

Codominance • In heterozygotes the phenotypes of both homozygotes is expressed • AKA both alleles are expressed equally • Ex. Human Blood Types Type A blood Type B blood Type AB blood Type O blood Genotype: IAi Genotype: IBIA Genotype: ii

Blood Type Prevelence

Multiple Alleles • More than 2 alleles exist for a certain trait • Ex Blood Typing – 3 alleles to determine blood type

Polygenic Inheritance • When a trait is controlled by 2 or more genes • Ex. Height – Controlled by several genes, explains why there’s a range of heights – Environmental factors also play a role

Genetics of Skin Color

Up till now… • All of the patterns of inheritance could be explained as long as one understands the patterns of inheritance for the trait in question • BUT there are some inheritance patterns that Mendel’s laws can’t explain

Sex Linked • Traits controlled by genes located on the sex chromosomes (AKA autosomes) • Ex. Color Blindness – Recessive allele located on the X chromosome N This is what a red/green color blind person would see. O R M A L Female genotype: XBXB or XBXb Female genotype: Xb. Xb Male genotype: XBY Male genotype: Xb. Y C O L O R B L I N D