This document discusses several genetic inheritance patterns beyond simple dominance and recessiveness:
1) Codominance - Both alleles contribute to the phenotype, such as a cow that is both red and white producing a roan coat color.
2) Multiple alleles - A single gene can have more than two alleles influencing a trait, such as four alleles determining rabbit coat color.
3) Sex linkage - Some traits are determined by genes on the X chromosome, making them more common in one sex, like color blindness being more prevalent in males.
1. • Incomplete Dominance
– One allele is not
completely dominant
over the other.
– Offspring shows
blending phenotype
– Eg: White flower
crosses with a red =
pink flower.
2. Beyond Dominant and Recessive
• Codominance
– Both alleles contribute to
the phenotype.
– Eg: Red cow X White
Cow = Roan Cow.
– Eg: blood type
I A IA IB IB
genotype or or
I A IB ii
IA i IB i
phenotype
phenotype A B AB O
3. Beyond Dominant and Recessive
• Multiple Alleles
Full
– One gene have more than two alleles
– Eg: Rabbit coat color, four alleles:
• C > cch > ch> c
– Eg: blood type, three alleles
• IA = IB > i
4.
5.
6.
7.
8. • Polygenic traits
– Several genes control the
trait.
– Wide range phenotypes.
– Eg: Skin color, height
9. Beyond Dominant and Recessive
• Sex linkage (x-linked)
– Some genes are present on the X
chromosome but missing on the
shorter Y chromosome.
10. Beyond Dominant and Recessive
1) Color blindness
– more common in males
than in females.
It is defined generally as an even mixture of white and pigmented hairs that does not "gray out" or fade as the animal ages
The genotype AaBbCc would produce the same skin color as any other genotype with just three dark-skin alleles, such as AABbcc
A person with normal color vision can see more than 150 colors. In contrast, some one with red green color blindness can see fewer than 25. For some affected people, red appear grray, others see gray instead of green
