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Non-Mendelian Inheritance

Non-Mendelian Inheritance. Not all traits exhibit simple dominant and recessive expression. Incomplete Dominance Multiple Alleles Codominance Polygenic Traits Environmental Effects. Incomplete Dominance.

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Non-Mendelian Inheritance

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  1. Non-Mendelian Inheritance

  2. Not all traits exhibit simple dominant and recessive expression. • Incomplete Dominance • Multiple Alleles • Codominance • Polygenic Traits • Environmental Effects

  3. Incomplete Dominance • Incomplete dominance – heterozygous phenotype is intermediate between that of either homozygote • Produces a blended phenotype

  4. Incomplete Dominance • A man with straight hair mates with a woman that has curly hair what is the chance of their offspring having wavy hair? Dad HH Mom hh x H H HH Straight h Hh Hh Hh Wavy h Hh Hh hh Curly 100% Wavy

  5. Codominance • Codominance - both alleles are expressed at the same time in the heterozygote • Ex: Rhone horse • Has both black and white hairs

  6. Example: Problem • You breed a white chicken with an Andalusian blue rooster (black and white feathers). What are the potential offspring? Dad BW Mom WW x B W BB Black W BW WW BW Andalusian W BW WW WW White 50% Andelusian; 50% White

  7. More than 2 alleles control trait. Diploid organism can only have 2 alleles. Example: Rabbit fur color C (wildtype), ch (himalayan), cch (chinchilla), c (albino) wildtype albino chinchilla himalayan http://www.catsandrabbitsandmore.com/home http://biomesblog.typepad.com/the_biomes_blog/2004/06/ http://didiermervilde.bestofbreeds.net/caviaandrabbits.html http://pantransit.reptiles.org/images/1998-02-07/ Multiple Alleles

  8. Multiple Alleles • Human Blood Type • 3 alleles -- IA , IB , and IO • IA and IB are codominant • IO is recessive • Type A blood can be IAIA or IAIO • Type B blood can be IBIB or IBIO • Type AB blood is IAIB - codominant state • Type O blood is IOIO

  9. Blood type • A woman with AB blood type has a baby with B blood type. Is it possible for a man with type A blood to be the father? If so what is the mans genotype? Dad IA - Mom IAIB x Type A blood can be IAIA or IAIO Type B blood can be IBIB or IBIO Type AB blood is IAIB - codominant state Type O blood is IOIO IA - IA IAIA IA- IB IAIB IB- Yes Dad must be IAIO

  10. Polygenic Inheritance • Wide range (continuum) of phenotypes • Human skin color • Height and weight • Two or more genes responsible for trait.

  11. Polygenic Inheritance Skin Color

  12. Environmental effects Color resembles snowy background in winter • The expression of some genes is influenced by environmental factors, such as temperature • Some alleles are heat-sensitive • Arctic foxes, cats, rabbits make fur pigment only when the weather is warm Color resembles tundra background in summer

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