Download incomplete dominance

Lesson 5
What is incomplete dominance?
In most games, there is a
stronger team and a weaker
team. Usually, the stronger team
wins. Some games end in a tie.
This shows that the teams are
equally matched.
Heredity is sometimes like this.
Most traits have a stronger,
dominant gene, and a weaker,
recessive gene.
The dominant gene usually
“wins”. The dominant trait shows
up in the offspring. The
recessive trait stays hidden.
Not all genes are completely
dominant or completely
recessive. The genes of certain
traits are equally strong. Neither
trait is dominant.
We say there is incomplete
dominance. In cases like these,
genes combine, and mix.
A mixture of the two genes
shows up. This kind of gene
combination is called blending.
There are three good examples
of incomplete dominance.
Four-o’clock Flowers
Four o’clock flowers are usually
red or white. Red and white are
equally strong traits. Neither
color is dominant. When a pure
red (RR) crosses with a pure
white (WW), the colors blend.
The offspring will have pink (RW)
flowers.
Shorthorn Cattle
In cattle, if one parent is pure red
(RR) and the other parent is pure
white (WW), the offspring will be
pink (RW).
The blended calf is called a
“roan”.
Andalusian Fowl
Some of these chickens have
genes for black feathers, others
have genes for white feathers.
Neither of these genes is
dominant. The offspring of pure
black (BB) and pure white (WW)
are gray (BW)
Many genes in humans also
show incomplete dominance.
They include genes for most hair
and eye colors.