MadSci Network: Genetics
Query:

Re: Incomplete dominance

Date: Tue Dec 8 17:51:29 1998
Posted By: Carl Mayers, Grad student, Plant Sciences, Cambridge University
Area of science: Genetics
ID: 910572858.Ge
Message:

Ok, let's take this step by step.

Firstly, let's say the the colour of the flower is controlled by this incomplete dominance gene. The gene comes in two alleles (different forms), and the flower will always have two copies of the gene (as it has two chromosomes, each containing the gene). Let's call these either R (red) or W (white)

As the flower colour is controlled by incomplete dominance the offspring will all be pink (half way between red and white). We now take this pink flower (RW) and cross it with a white flower (WW). The offspring get one of their genes from parent 1 (white), so one will always be a white gene. The other gene will come from the other parent (pink, RW), and it has a 50/50 chance of being either a white or a red gene.

This means the genotypes of the offspring here will be either WW or WR. This means that half the new plants will have white flowers (WW) and half will have pink flowers (RW).

Gene R W
W RW WW
W RW WW
It was this sort of experiment which originally led to the discovery of genes being seperate, indivisible things. You can't make a pink flower whiter or redder by crossing it with a white or red flower. You can only get white, red or pink, and never any more blending than this.

Here's a good site to look at for more information: Gene interactions

Hope this helps!

All the best, Carl


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