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Lecture 15

GN 301 Lecture Notes - Lecture 15: Genome-Wide Association Study, Abo Blood Group System, Conjoined Twins

Course Code
GN 301
Marian- Elizabeth B.Gardner

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3.5 Multifactorial Inheritance
Tuesday, October 31, 2017
10:16 AM
Polygenic Inheritance
o Many genes control one trait
Effect of just oe is’t uch
No dominance of one allele
o Phenotype is combo of env and genotype
o Continuous variation among diff people
No specific categories of phenotypes
Ex:Height, limb length
o Bell curve of phenotype vs frequency
o Eye Color
Two genes for the green blue lipochrome and two genes for the brown melanin
Additional genes for streaks and light and dark regions
o Skin color
3 genes involved in skin color; can be a mix of colors
Threshold Traits
o Each genotype can add risk factors and at a certain point where factors exceed threshold,
the disorder is seen
o If given dom allele gives 5 risk factors, recessive 2 risk factors, and disease needs 25,
someone who is AABBCC has 6 alleles x 5 risk factors= 30 so yes they have disease
o Monozygotic= identical
Acceptance of reciprocal skin grafts
Possible to have separate amnions or chorionic depending on when embryo splits
66% share chorion but not amnion
Is not inheritable
o Dizygotic=fraternal
Immune response due to WBC
Increase with age of mother
Ovulation irregular
Super ovulation can be passed down through sons
o Super Twins= combo of identical and fraternal twin event that occurs in multiples during
one birth
o Conjoined Twins
Chang and Eng Bunker
From Siam Thailand
o Proportion of the phenotypic variance that is due to genetic effects (0 means no var due to
genes, 1 means all due to genes)
o Variance in phenotype is combo of genotype and environment
o Twins used to study this Nurture vs nature
o Traits
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