A Case Study in Genetics

Probably no one but me will find this interesting, but I love stuff like this!

Last year we planted snapdragons in our front bed. We bought them as annuals, but we had heard they could be perennials depending on the location. When they seeded, I helped them by shaking out their seeds. It worked. We have more snapdragons this year than we had last year, and some of them are huge.

In Mendel's classic pea experiment, flower color was determined by dominant/recessive genes. The purple flowers were dominant. A plant with two alleles (genes) for purple would be purple. A plant with one purple and one white allele would be purple, and a plant with two white alleles would be white.

Snapdragons exhibit a variation of the first law of genetics. They follow co-dominance, meaning a first generation flower exhibits both alleles. We originally bought three colors of snapdragons: yellow, pink, and red. I was interested in what colors came up this year, the first generation.

Here are the original colors.

Red

Pink

Yellow

Here are the new colors:

A red/yellow flower

A red/pink flower (It appears lighter in the photo than it really is. Look behind it to see some darker shades of red/pink mix).

Yellow/pink flowers

In addition to the blending, some flowers exhibited both colors distinctly in one flower. I debated about whether the flowers were following co-dominance or incomplete dominance and decided on co-dominance because of this picture.

In co-dominance, all the first generation flowers should be mixes, as in red and white parent flowers should make all pink first generation flowers. The second generation should have a ratio of 1/4 red, 1/2 pink, 1/4 white. Our flowers weren't all cross-pollinated with other colors, so we still had some of the original colors come up.

Pretty cool stuff.