11.2 & 11.3 Complex Patterns of Inheritance

Complex Patterns of Inheritance

1. 11.2 Complex
Inheritance

2. A. Incomplete Dominance
Heterozygous phenotype is
an intermediate phenotype
between the two
homozygous phenotypes
EX. Red x white = pink

3. B. Codominance
Both alleles are expressed in the
heterozygous condition
Example: Sickle-Cell Anemia
People who are homozygous have
abnormal red blood cells that are shaped
like a half moon

•Hemoglobin differs by
one amino acid
•Results in slow blood
flow and blocked vessels

5. Those heterozygous for this trait
produce both kinds of blood cells
(normal and sickle)—these individuals
can lead relatively normal lives.
 most common in black Americans
whose families originated in Africa and
white Americans whose families
originated in countries surrounding the
Mediterranean Sea
 1 in 12 African Americans is
heterozygous for this trait

7. C. Multiple Alleles
Example 1: Blood Type
a.The gene I has three alleles:
I
A,
I
B,
& i
b. These alleles determine your
blood type: A, B, AB, and O

8. Blood Types

9. Importance of Blood
Typing
Your immune system
recognizes the red blood cells
that you have.
If cells with a different protein
enter your body, your immune
system will attack them!

10. Blood Types
Genotype Surface
Protein
Phenotypes
I
A
I
A
or I
A
i A A
I
B
I
B
or I
B
i B B
I
A
I
B
A and B AB
ii none O

11. Example 2: Coat Color
of Rabbits
Multiple alleles can
demonstrate a hierarchy of
dominance
In rabbits, four alleles code
for coat color: C, c
ch
, c
h
, and c.

12. Coat Color of Rabbits
Light gray
Dark gray
Chinchilla
Albino
Himalayan

13. D. Epistasis
Variety is the result of one allele
hiding the effect of another allele
Example: Coat color in labrador
retrievers varies from yellow to black
No dark pigment present in fur Dark pigment present in fur
eebb
eeB_
E_bb
E_B_

14. E. Sex Determination
Sex
chromosomes
determine an
individual’s
gender

15. e. Sex Linked Traits
Examples:
1.Color Blindness
Carried on the X chromosome

16. 2.Hemophilia; Inability of blood
to clot
Carried on X chromosome

17. f. Polygenic Inheritance
1.Example: skin color
2.Variation in skin color
indicates that between 3 and 4
genes are involved

18. 11.3 Chromosomes and
Human Heredity

19. A. Changes in
Chromosome Number
What would happen if an
entire chromosome was
missing or if you had an extra
chromosome?
These mistakes often happen during
meiosis.
Nondisjunction =chromosomes fail
to separate properly during cell
division

20. 1. Unusual Numbers of
Autosomes
Most people have 23 pairs of
chromosomes;
•22 autosome pairs & 1 pair of
sex chromosomes
Some people have an extra
chromosome (47 instead of 46)

21. Down Syndrome
Caused by an extra 21
st
chromosome
Karyotypes are used to locate extra chromosomes.

22. Unusual Number of Sex
Chromosomes
1. Many problems may exist:
X missing
XO=Turner’s Syndrome, OY=death
Extra X:
XXX=nearly normal female,
XXY=Male with Klinefelter’s Syndrome
Extra Y:
XYY=normal or nearly normal male
2. Any individual with at least one Y is
male, and any individual without a Y is a
female.