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Complex Inheritance Patterns

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.

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Complex Inheritance Patterns

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  1. Complex Inheritance Patterns

  2. Simple Dominance

  3. 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

  4. Incomplete Dominance

  5. 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

  6. Codominance

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. Sex-linked inheritance

  13. 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?

  14. 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-acidic Pink-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

  15. 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 freckles http://j-walkblog.com/index.php?/weblog/2006/08/04/

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