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Complex Inheritance Patterns. Simple Dominance. Incomplete Dominance. One allele does not completely dominate the other Get a “blending” effect Three phenotypes- the heterozygous genotype has its own phenotype. http://www.emc.maricopa.edu/faculty/farabee/biobk/incomdom.gif. - PowerPoint PPT Presentation
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Complex Inheritance Patterns
Simple Dominance
Incomplete Dominance • One allele does
not completely dominate the other
• Get a “blending” effect
• Three phenotypes- the heterozygous genotype has its own phenotype
http://www.emc.maricopa.edu/faculty/farabee/biobk/incomdom.gif
Incomplete Dominance
Codominance
• Both alleles are equally dominant
• Three phenotypes• Two completely different
letters used• Example: AB blood type checkered chickens
roan cattle
http://users.adelphia.net/~lubehawk/BioHELP!/rw01.jpg
Codominance
Multiple Alleles• Genes that have more than two allele
forms within a population (remember that individuals can only have
two alleles)Examples: fur color in rabbits, blood
types in humans
ABO blood type• In human blood
there are 3 different alleles that control blood type
• This results in 4 phenotypes.
A and B are dominant over O
A and B are codominant
http://faculty.ircc.edu/faculty/tfischer/images/blood%20types.jpg
Frequency of blood types(includes Rh factor)
http://images.google.com/imgres?imgurl=http://bloodcenter.stanford.edu/images/bloodtypes.jpg&imgrefurl=http://bloodcenter.stanford.edu/about_blood/blood_types.html&h=249&w=400&sz=32&hl=en&start=6&tbnid=cLwigs-NpY07PM:&tbnh=77&tbnw=124&prev=/images%3Fq%3Dblood%2Btypes%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG
Polygenic Traits• Many genes
controlling one trait• Most of the traits we
see in humans are this type of pattern
Examples: hair color, skin color, height, etc
• Show a wide range of phenotypes that strengthen in intensity
http://www.svgs.k12.va.us/Courses/MolecularBiology/powerpoints/genetics14_files/slide0093_image056.gif
Sex-linked Inheritance
• Genes that are found on the X chromosome
• Traits carried on the X chromosome are expressed more in males because they only have one X chromosome (XY) compared to females (XX)
• Examples: colorblindness, Hemophilia A, Duchenne muscular dystrophy
Sex-linked inheritance
Colorblindness
• As in other sex-linked traits, the disorder is passed on by mothers to their sons
• Fathers can only pass on the trait to their daughters
How do doctors test for color vision deficiency?
Nature vs. Nurture?
• The environment can play an effect on how genes are expressed
• Climate, soil, and food nutrition can affect growth of an organism
Ex. Hydrangeas are affected by soil pH
Blue-acidicPink-basic
http://images.google.com/imgres?imgurl=http://www.goodgardenbooks.co.uk/GGB/Images/Hydrangeas.jpg&imgrefurl=http://www.goodgardenbooks.co.uk/GGB/HTML/Hydrangeas.html&h=225&w=300&sz=23&hl=en&start=8&tbnid=FipzLSroBC9IwM:&tbnh=87&tbnw=116&prev=/images%3Fq%3Dhydrangeas%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG
Gene Linkage• Some traits seem to always be together
because they are close together on the same chromosome.
• Known as linked genes or linkage groups
Ex. Red hair and freckleshttp://j-walkblog.com/index.php?/weblog/2006/08/04/