Genocopy is a trait that is a

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

copy of a genetic trait but is caused by a different

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

. When a genetic

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...

in one locus results in a

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

similar to one that is known to be caused by another mutation or genotype in another locus, it is said to be a genocopy. However, genocopies may also be referred to as "genetic mimics", in which the same mutation or specific genotype can result in two unique phenotypes in two different patients. The term “Genocopy” was coined by Dr. H. Nachstheim in 1957, in which he discusses “false” phenocopies. In comparison to when a phenotype is the result of an environmental condition that had the same effect as a previously known genetic factor such as mutation. While offspring may inherit specific mutations or genotypes that result in genocopies, phenocopies are not heritable. Two types of elliptocytosis that are genocopies of each other, but are distinguished by the fact that one is linked to the Rh blood group locus and the other is not. The way to distinguish a recessive genocopy from a

caused by a different

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

would be by carrying out a

test cross Under the law of dominance in genetics, an individual expressing a dominant phenotype could contain either two copies of the dominant allele (homozygous dominant) or one copy of each dominant and recessive allele (heterozygous dominant). By per ...

, breeding the two together, if they

F1 hybrid An F1 hybrid (also known as filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where the term F1 crossbreed may be used. The term is somet ...

segregates 1:2:1 then we can determine that it was a genocopy.

Examples

Mitochondrial diseases

Since Mitochondria carry out such a variety of functions in different tissues, there are often hundreds of Mitochondrial diseases that might be harder to diagnose in early stages. Considering that there is a complex relationship between cells and genes to have metabolism at its optimum, identical Mitochondrial DNA mutations may not show up as identical diseases. Genocopies are often seen as diseases that might be caused by the same mutation but do not result in identical expression. Diseases associated with

mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondrion, mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mit ...

are often as a result of mutations in

tRNA Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino a ...

that play a role in Mitochondrial protein synthesis. These mutations that change protein-encoding genes or both. How each category of cause of Mitochondrial disease produces genocopies is still unknown.

DiGeorge syndrome

The genocopy event between TBX1 and 22q11.2 mutations is one that shows grave symptoms. The 22q11.2 mutation leads to DiGeorge or velocardiofacial syndromes. Similarly, the mutations in the TBX1 genome exhibit the same symptoms. The TBX1 haploinsufficiency is responsible for many of the traits that are also seen in 22q11.2 mutations. It has 2 mutations that are similar to the two mutations of 22q11.2 - deletion and duplication. The first mutation is L411P and is a

de novo mutation A de novo mutation is any mutation/alteration in the genome of any organism (humans, animals, plant, microbes, etc.) that wasn't present or transmitted by their parents. This type of mutation (like any other) occurs spontaneously during the process ...

. This mutation affects a conserved amino acid within a putative transactivation domain and is likely to affect the protein's functionality. The second mutation is one that converts a

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached ...

thymine Thymine () (symbol T or Thy) is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine n ...

in the 5’ UTR region of the TBX1 gene. This mutation increases TBX1 translational efficiency during key points in development, which is the functional equivalent to 22q11.2 duplication. This shows us that genocopy is not just a discrete genomic event but can also be seen in serious diseases.

References

Classical genetics {{Genetics-stub

Examples

Mitochondrial diseases

DiGeorge syndrome

See also

References