codominant or dominant spiders

[littleindiangirl]

Very very very close. You have it just about correct.

so because the spider phenotype is fully expressed after only one breeding, the phenotype or spider characteristic is considered dominant.

I get what your saying in the whole, but the terminology is off. Since the spider gene is fully expressed when heterozygous (only one copy), then it is considered dominant.

the genotype of the spider however, is codominant, so calling the spider characteristic dominant is only a way of saying there is no further expression of this phenotype.

I'm not sure if we could consider the gene co-dominant or incomplete, or just dominant in reference to terminology. I have never understood why people consider it just a dominant. Maybe someone wants to step up to the plate and explain that one.

Generally speaking, if you were in a biology class, co-dominant and incomplete dominant means something different than what we think of in our everyday hobbyist lingo.

http://www.emc.maricopa.edu/faculty/...ninteract.html

Codominant alleles

Codominant alleles occur when rather than expressing an intermediate phenotype, the heterozygotes express both homozygous phenotypes. An example is in human ABO blood types, the heterozygote AB type manufactures antibodies to both A and B types. Blood Type A people manufacture only anti-B antibodies, while type B people make only anti-A antibodies. Codominant alleles are both expressed. Heterozygotes for codominant alleles fully express both alleles. Blood type AB individuals produce both A and B antigens. Since neither A nor B is dominant over the other and they are both dominant over O they are said to be codominant.

(or a red and white flower when crossed will give a red and white spotted flower because both colors are dominant)

Incomplete dominance

Incomplete dominance is a condition when neither allele is dominant over the other. The condition is recognized by the heterozygotes expressing an intermediate phenotype relative to the parental phenotypes. If a red flowered plant is crossed with a white flowered one, the progeny will all be pink. When pink is crossed with pink, the progeny are 1 red, 2 pink, and 1 white.