Download Alternative Types of Inheritance

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: IBi
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
C
O
L
O
R
M
A
L
Female genotype: XBXB or XBXb
Female genotype: XbXb
Male genotype: XBY
Male genotype: XbY
B
L
I
N
D