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

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.

12. Beyond Dominant and Recessive
2) Haemophilia
– unable to clot blood