Why reginae hybrids look like pure reginae


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Abgeschickt von Lukas Hunziker am 05 November, 2004 um 22:34:29

Hello,

A lot has been discussed about the appearance of reginae hybrids. There was the question why they all look like pure reginaes. The explanation is really simple. There is a glossary at the bottom if you don’t understand a word.

Incomplete dominance is basically just a blending of traits: It describes the general situation in which the phenotype of a heterozygote is intermediate between the two homozygotes. Just think of mixing paints, red and white make pink. Red does not totally block (dominate) the white. Instead, there is incomplete dominance, and we end up with something in-between, the color pink.
The genotype is: (CC) x (MM) = (CM) (No gene is recessive, so it is an intermediate individual)
The letters in the brackets are chromosomes, one letter for one chromosome
This is the general situation with crossing Cypripedium hybrids. With the exception of Cyp.reginae, perhaps also other Cypripediums which have not yet been crossed.

The explanation with Cyp.reginae hybrids is easy:
Dominant vs Recessive Traits.
A homozygous C.reginae parent (RR) with the allele for the reginae flower is crossed with a homozygous Cypripedium acaule parent (aa) with the allele for acaule flower. Each plant makes gametes of only one kind, either R or a (capital R for the dominant reginae and small a for the recessive acaule). These gametes combine to form the first filial generation (F1). All F1 plants are heterozygous and have the genotype Ra. The genotype is the genetic construction of an organism or combination of alleles. What do the plants lool like in F1? All of them have reginae flowers. The observable property or phenotype is reginae.

So the explanation is that there are genes in nature which are dominant. C.reginae genes are dominant genes. Other Cypripedium species are not as dominant as reginae, they have recessive genes.
The final plant differs a little bit from a pure reginae because the hybrid is heterozygous and not homozygous like C.reginae.

Next step:
If you would cross a Cypripedium ‘Prof. Karl Robatsch’ with another one, you could make a F2 Hybrid. There would be 25% pure reginae, 50% C.’Prof. Karl Robatsch’ and 25% acaule!
That are the laws of inheritance.

Glossary:
Allele: Alternative forms of a gene at a given region of a chromosome; alleles are inherited seperatly from each parent.
Dominant allele: An allele that determines the phenotype in a heterozygous individual carrying another recessive allele. A dominant allele can suppress a recessive allele. Thus, if R is dominant over a, then RR and Ra have the same phenotype.
Recessive allele: An allele whose phenotypic effect is not expressed in a heterozygous individual.
Homozygous: Describes an individual having two identical alleles for a given gene. An individual may be homozygous dominant (RR) or homozygous recessive (rr). Individuals who are homozygous for a trait are referred to as homozygous
Heterozygous: Refers to an individual containing different alleles for a given gene. Heterozygous organisms have two different allels of a gene. Individuals who are heterozygous for a trait are referred to as heterozygous.
Phenotype: The characteristics of an individual produceed by the interaction of its genetic material and the environment.


Yours sincerely 

Lukas


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