Genetics4.3.12,10.3.1,10.
3.2
David Barkley
Taylor Turner
Polygenic Inheritance
 Polygenic
inheritance is the inheritance of
a characteristic that is controlled by more
than one gene.
 Human traits that show continuous
variation include weight, height and skin
color.
Polygenic Inheritance
 This
means that something simple, like skin
color, is affected by more than one gene
from ones parents. Each allele of a
polygenic character will offer a little bit of
information to the whole phenotype.
Polygenic Inheritance
 Human
skin color is a good example to
visually see how more than one gene can
affect appearance.
Polygenic Inheritance

In humans there are at
least three genes
coding for skin color.
Each skin color gene
has two forms; one
form codes for high
levels of melanin
production, and the
other form codes for
low levels of melanin
production
Polygenic Inheritance
 Wheat
 Kernel
color in wheat is determined
by two gene pairs
 crossing individuals with the
phenotype extremes yield offspring
that are a 'blend' of the two parents
Polygenic Inheritance
 When
these homozygotes are crossed the
offspring are all double heterozygotes
AaBb
 two double heterozygotes are crossedhttp://staff.jccc.net/pdecell/evolution/pol
ygen.html
4.3.12 Deduce
the genotypes
and
phenotypes of
individuals in
pedigree
charts.
Pedigrees:
 Are
used to illustrate the mode of
inheritance (dominant or recessive)
 Give clues to the mode of inheritance of
the disease
 Show potential threat to other family
members
Phenotypes:
 Observable
and measurable charaterics
in an organisms
 Effects of genetic coding and
environment
Ex:
eye color
Genotypes:
 Genetic
composition of organisms
 With respect to the specific traits they describe
 Refers specifically to genetic code (environment
has no effect)
Type of
Inheritance
Autosomal Dominant Inheritance
Requires
only one parent to
carry the dominant gene in
order for children to be
affected.
Autosomal Recessive
Inheritance
Requires
for both parents must
carry the recessive gene for
offspring to be affected.
X-Linked Dominant & Recessive
Inheritance
 More
common in boys because they only
need one gene
A
mother gives the dominant or recessive
gene male offspring and the father gives
the Y chromosome.
Pedigree Vs. Punnett Square
A
punnett square is used to determine the
out come of two alleles being crossed
 Contrarily
a pedigree is used to find
modes of inheritance for genetic diseases
Extra Pedigree Practice
 www.zerobio.com/drag_gr11/pedigree/p
edigree_overview.htm
I’M MY OWN
GRANDPA
Works Cited
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"Define polygenic inheritance - IB Biology Syllabus." IB Biology Syllabus Home - IB Biology
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<http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookgeninteract.html>.
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<http://www.biologyforlife.com/course%20info/Syllabus/Syllabus.htm#Topic_10:__HL_Geneti
cs>.
"Polygenic inheritance." JCCC Staff and Faculty Pages. N.p., n.d. Web. 13 Feb. 2012.
<http://staff.jccc.net/pdecell/evolution/polygen.html>.