Monday, October 11, 2010

Incomplete Dominance

So far according to Mendel's rules.....

Genes have two options (aka alleles): dominant and recessive.

Dominant traits always outweigh or mask the recessive traits.

Phenotype (outward appearance) is only dominant or recessive.


HOWEVER!!!!!

As we have pursued genetics as a science further, we quickly realized that not all traits are inherited in such a simple pattern.

Patterns that follow a similar pattern as the one Mendel put in place, but have some special circumstances are known as Non-mendelian patterns of inheritance.


This blog entry will focus on the pattern known as incomplete dominance.

 http://www.visionlearning.com/library/module_viewer.php?mid=129
In the picture above you should see 3 different colored snapdragon flowers: red, pink, and white.  The color of this flower is determined by a similar set of alleles as simple dominance, but the way in which those genes expressed differs.

In Punnett squares before we saw fewer phenotypes than genotypes because Aa and AA would reflect the same dominant phenotype.

In snapdragons, inheritance is expressed with a slight twist.  Homozygous dominant flowers are red (RR) and homozygous recessive flowers are white (rr), but the heterozygote (Rr) is a blend of dominant and recessive or in this case pink.

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