Why is there no Dumbo gene in pet rats

Kathrin Guttmann General, Knowledge, Breeding & Genetic

...and this gene may not be recessive.

I admit it: the title of this article is somewhat provocatively written. Talk because not all potential breeders of a "Dumbo-Gen" or it, that this "Dumbo-Gen" is recessive? What the hell these completely mistaken assertion, there would be no Dumbo gene?

In the parlance under color rat breeders, unfortunately, quite a negligence has come to be, when it comes to the correct use of terminology of genetics. In part, this may be because, that one has replaced complex descriptions in simple terms. However, the impression, that there are more and more breeders, that no longer know, as the correct use of the terminology is, which is really necessary for a deeper understanding of the relationships in genetics. The correct use of the terms chromosome, locus, Gen, Allel, Genotype and phenotype I will explain below using the example of Dumbo Rat.


Genetic terms the example of Dumbo

In the ears of Dumbo rat is a phenotype, ie a outwardly visible appearance in feature. The phenotype includes all distinct features of an organism - morphological, physiological and behavioral characteristics. It is based on the genetic make-up and is caused by environmental factors and partly to chance (, e.g. due to. in the spotting of cows) influenced.

This phenotype is a certain genotype basis, the of all genes of an organism consists. The genotype includes all chromosomes the nucleus, but also extra-chromosomal DNA as e.g.. the DNA in the mitochondria. we will ignore these extra-chromosomal DNA here.

The chromosomes contain Gene, on certain loci (Locus or locus, Soon locus or locus, plurality loci) lie.


Previously it was assumed, that each gene is a feature of (A gene is a feature-hypothesis) encodes and it also corresponds to, when one speaks of a "Dumbo gene", So a gene with the feature describes, which is to encode it. One reason for this may be my opinion, that we mostly talk when looking at the genetics of color rat breeders at the level of Mendelian genetics and this use of the term was completely common in Mendel. Only in the 1940s, this one-gene-one trait hypothesis was replaced by the one-gene-one-enzyme hypothesis, have developed the Beadle and Tatum1)George W. Beadle, Edward L. Tatum: Genetic Control of Biochemical Reactions in Neurospora. In: Proceedings of the National Academy of Sciences of the United States of America. Bd. 27, No.. 11, 1941, S. 499–506, PMID 16588492, PMC 1078370.


Today we know, that genes Not encode one to one features. Instead, they are assumed, that the polypeptides encoded in genes (A gene, a polypeptide hypothesis). Polypeptides are the building blocks of proteins (proteins). For this reason it is also not correct, to speak of a "Dumbo gene". In the case of the feature Dumbo is the gene H6 Homeo Box 1 (Hmx1), which provides on the synthesized polypeptides by him in a chain of biochemical reactions during the embryonic for, that Dumbo ears arise - or not arising.


Lots Gene namely come in several variants. These variants are called Allele. alleles State forms of genes, lying on certain gene loci. The HMX1 has in pet rats two known alleles, on the corresponding locus, which appears in Title 79.0-84.7 Mb on chromosome 14 is, can be. One of these alleles encoding for the expression of standard ears necessary polypeptide and is in the consideration of the characteristic ear shape with You (capitalization) abbreviated. The second allele does not encode this polypeptide or. encoding another polypeptide and is described in the consideration to characteristic level with you (lowercase) abbreviated.

The allele is you against the allele you dominant (Therefore letters in capital letters), is the other way around the allele you recessive compared with the allele You (Therefore letters to lowercase). So one can not speak of dominant genes, because the gene is like the preamble to all on the corresponding locus alleles possible. Correctly, it is called or dominant. recessive alleles. Furthermore, the Attributes dominant and recessive always relative to use, as it occurs in the presence of several possible alleles, that e.g.. Alllel A versus B allele dominant, but is recessive to allele C. For simplicity, we want here but stay with only two possible alleles continue.


Rats have in their body cells duplicate sets of chromosomes how we humans also. The term homologous chromosome called a chromosome, that matches another chromosome in the form and sequence of the genes. Each diploid cell has a set of homologous chromosomes - one from the father and one from the mother. That means, that each chromosome and thus each locus is duplicated. It may each be the same or different all on the two mutually corresponding loci. If the same alleles in front, they say, that an organism homozygot (reinerbig) for the corresponding allele is. Are different alleles ago, the organism heterozygot (mischerbig) for allele. Dominant alleles ensure, that a feature is already then pronounced, if this allele is present only on one chromosome and the organism is heterozygous for this allele. Recessive alleles must be present on both mutually corresponding loci, to lead to the expression of the corresponding feature, that is, the organism must be homozygous.

So correctly you would have for a dumbo rat formulate:
The feature "Dumbo" because of the presence of the homozygous compared to the corresponding wild-type allele You recessive du allele on the locus of the H6 Homeo Box 1 Gene on the locus in Abshnitt 79.0-84-7 Mb of chromosome 14 pronounced.

References   [ + ]

1. George W. Beadle, Edward L. Tatum: Genetic Control of Biochemical Reactions in Neurospora. In: Proceedings of the National Academy of Sciences of the United States of America. Bd. 27, No.. 11, 1941, S. 499–506, PMID 16588492, PMC 1078370