Living Environment Translated Arabic 2014 | Page 60

 Incomplete dominance is when both alleles for a trait are equal.
o There are no dominant or recessive alleles.
o Two different uppercase letters represent each allele.
( Ex: R= red W= white)
o The genotypes follow the same pattern as regular dominant/
recessive crosses:
 RR
 WW
 RW
o The phenotypes DO NOT follow the same patterns as regular
dominant/ recessive crosses.
 RR= looks red
 WW= looks white
 RW= looks pink ( it is a blend of the two allele colors)
 Many traits are controlled by two or more alleles.
 Polygenic inheritance is the name given to traits that are controlled
by more than two alleles. ( Ex: eye color, hair color, blood type)
 Autosome- chromosomes that contain genes for characteristics not
directly related to the sex of the organism. Humans have 22
autosomes.
 Sex chromosome- directly controls the development of the sex of
the offspring.
o XX- female
o XY- male