Figure 2: Basic types of genetic alopecia
Hairless rats have higher oxygen consumption and higher basal metabolic rates than haired rats.
Double rex is 2 doses of the dominate rexing genes (re, cu-1, or Cu-2) A double rex will exhibit very limited hair/fuzz or sparse hair particularly on the head, the hind end, and the legs. At times it will somewhat come and go. Patchwork Hairless is also a double dose of the rexing genes. They will have patches of short fuzz that can come and go and often appear over different parts of the rat’s body.
There are various true types of genes that cause hairlessness in rats. Some are associated with certain health/breeding issues. Many lines in the pet rat breeding community have overcome these issues. The hairless genes are recessive and will produce hairless rats when bred only with another hairless/or carrier.
The Genes that give us Genetic Alopecia
Mock Hairless/Double rexed/Patchwork Hairless
(Often sparse hair on head and posterior that will come and go)
The gene Re – Rexing locus (dominant)
Re/Re = rexed or mock hairless
Re/re = rexed coat
re/re = standard coat
Cu1 & Cu2
The gene Cu – Curly Locus (dominant)
Cu/Cu = curly or patchwork hairless
Cu/cu = curly
cu/cu = standard coat
True Type Hairless
(Only showing *at most* curly whiskers. This type has been reported to have some lactation problems.)
The gene Hr – Hair locus (recessive)
Hr/Hr = standard coat
Hr/hr = hairless carrier
hr/hr = Hairless
(A spontaneous lab mutation discovered in 1994 at the lab in CCSU (Central Connecticut State University , http://www.ccsu.edu/technology/mulrooney/research/reshome.htm — Archived page from 2008-07-06 (via the Wayback Machine)). Shorn rats are hairless These rats have abnormal hearts and kidneys which result in a short life span and don’t tend to live as long as other rats. The life expectancy is only 12-14 months of age.)
The gene shn – Nude Locus (recessive)
Shn/Shn = standard coat
Shn/shn = shorn carrier
shn/shn = shorn hairless
The gene Fz – Fuzzy locus (recessive)
Fz/Fz = standard coat
Fz/fz = fuzzy carrier
fz/fz = fuzzy hairless
(Chromosome 10) AKA- rat athymic nude or Winged-helix nude (Whn) (Hairless with lowered immune function due to the lack of a thymus gland can carry viral infections sub clinically)
The gene Rnu- recessive
Rnu/Rnu = standard coat
Rnu/rnu = rowlette nude carrier
rnu/rnu = rowlette nude hairless
(predicted chromosome 1)
(Mutation developed by Charles Rivers Labs)
The gene Fr- recessive
Fr/Fr = standard coat
Fr/fr = frizzy carrier
fr/fr = frizzy hairless
- Ahearn, K., Akkouris, G., Berry, P., Chrissluis, R., Crooks, I., Dull, A., Grable, S., Jeruzal, J., Lanza, J., Lavoie, C., Maloney, R., Pitruzzello, M., Sharma, R., Stoklasek, T., Tweeddale, J., King T. (2002). The Charles River “hairless” rat mutation maps to chromosome 1: allelic with fuzzy and a likely orthologue of mouse frizzy. J Hered, 93(3), 210-3. Retrieved December 24, 2008, from the Medline database.
- Boardman, B., & Boardman, L. (n.d.). Rat Genetic Code Basic Explanation. Retrieved December 24, 2008, from https://www.boardmanweb.com/rattery/geneticbasics.htm.
- Genetics Tutorial. (n.d.). Retrieved December 24, 2008, from http://www.geocities.com/Petsburgh/7989/rats/genetics.html.
- The Rat Genome Database. (n.d.). Retrieved December 24, 2008, from http://ratmap.gen.gu.se/.
Genetic Resource courtesy of Bellaratta’s Nest Rattery