1. Complex Patterns
of Inheritance

2. 1. Incomplete Dominance
The heterozygous phenotype is an intermediate
phenotype between the two homozygous phenotypes.

3. 2. Codominance
Both alleles are expressed in the
heterozygous condition.
Example:
-Changes in hemoglobin cause
red blood cells to change to a
sickle shape.
-People who are heterozygous
for the trait have both normal
and sickle-shaped cells.

4. Cross two people that carry an allele for normal cells
and an allele for sickle cells. Notice all are represented by
capital letters. N S NN NS SS
What type of cells would each individual have?

5. 3. Sex determination
Sex chromosomes determine gender.
Non-sex chromosomes are called autosomes.

6. -The X chromosome contains genes for many traits,
while the Y chromosome only carries a few genes
related to the development of male characteristics.
-Traits that are carried on the X chromosome are
called sex-linked or X-linked.
Examples of x-linked traits include hemophilia and
red-green color blindness.

7. Cross a non-colorblind female with a non-colorblindXN Xn
XN XN
XN Xn Y
XNY
Xn Y
What is the genotypic ratio?
What is the phenotypic ratio?

8. 4. Multiple Alleles
More than two alleles are possible for a given trait.
Example:
Human blood type – there are three possible alleles: A B O

10. Blood Cross IA IB
IAIB
IB IB i
IAi
IBi
What is the genotypic ratio?
What is the phenotypic ratio?

11. Example – Coat color in rabbits
Multiple alleles can demonstrate a
hierarchy of dominance.
In rabbits, four alleles code for coat color:
C, cch, ch, and c.
What can you learn from the way that the
alleles are written?
Rabbits – light gray, dark gray, chinchilla,
albino, himilayan

12. 5. Linkage Group – When genes are located on the
SAME chromosome they are said to be in
a linkage group.
-In a linkage group the genes travel together during
meiosis and therefore do not follow the Law of
________________.
-Linkage groups can be broken during the process
of _________________ while meiosis occurs.
-The closer together genes are on a chromosome, the
less likely that they will . . .

13. 6. Polygenic traits
Traits where multiple pairs of genes control the trait.
What other traits may be polygenic?

14. 7. Pedigree -A diagram that traces the inheritance of
a particular trait through several generations