Transcript Complex Inheritance of Human Traits

Complex
Inheritance of
Human Traits
Codominance in
Humans
 Phenotypes
of both
homozygotes are
produced in the
heterozygote
 Recall the checkered
rooster
 Sickle-cell anemia
Sickle-cell Anemia
 Disorder
where red blood cells
are sickle shaped
 Normally concave
 Shorter life span and can slow
bloodflow or block small vessels
 1 in 12 African Americans is
heterozygous for the disorder
Malaria
Cell
Sickle
Multiple Alleles in
Humans
Blood types
 Can be A, B,
AB, or O

Type A
The IA allele is
dominant to i
 IAi or IAIA will
give you type A
blood
 Surface protein
A is produced

Type B
The IB allele is
also dominant
to i
 IBIB or IBi will
=type B blood
 Surface protein
B is produced.

Type AB
 The
IA and IB
alleles are
codominant to
each other
 IAIB you will
have type AB
blood
 Will produce
both surface
proteins
Type O
The i allele is
recessive
 Produces no
surface
molecule
 Homozygous
ii you have
blood type O

Sex-Linked Traits in
Humans
 Traits
that are
determined by genes that
are carried on the sex
chromosomes
 Most of these genes are
located on the X
chromosome
Red-green Color
Blindness

People who
have redgreen color
blindness
can't
differentiate
these two
colors
Hemophilia: An X-linked
disorder
 Blood
fails to clot normally
because of a deficiency or
abnormality of one of the
clotting factors
 1 male in every 10 000 has
hemophilia but only about one
in 100 million females
 Why?
Polygenic Inheritance in
Humans
 These
kinds of traits
usually represent a range
of variation that is
measurable
 Color variations in
human eyes
 Skin color
Changes in Chromosome
Numbers
 Unusual
numbers of
autosomes
 Down syndrome: Trisomy 21
 Unusual numbers of sex
chromosomes
•Turner’s Syndrome and
Klinefelter's Syndrome