Although most Holstein cattle are either black with white spots or red with white spots,
two new coat colour traits called Variant Red (VR) and changeling, have recently been
recognized by Holstein Canada. Variant red cattle look the same as red and white Holsteins but
VR appears to be inherited as a dominant trait. Changeling cattle are born red and turn black by
adulthood. Candidate genes for changeling included melanocortin 1 receptor (MC1R), agouti
signalling protein (ASIP), attractin (ATRN), and melatonin receptor 1A (MTNR1A). Candidate
genes for variant red included these same genes and β-defensin300 (putative K locus).
Polymerase chain reaction restriction fragment length polymorphisms (PCR-RFLP) and
sequencing were used to genotype single nucleotide polymorphisms (SNPs), which were recently
discovered in our lab, for use in determining co-segregation in appropriate families. Cosegregation
analysis excluded MC1R, ASIP, ATRN, or MTNR1A for changeling and VR,
assuming single gene inheritance. Microsatellites and SNPs were used to map VR to a region on
BTA27 surrounding and including β-defensin300 (LOD = 3.255). Cattle β-defensin300 was
characterized from genomic DNA and mRNA from skin and appears to be homologous to canine
β-defensin103 which is involved in black/red coat colour differentiation in many dog breeds.
Although no mutations were found in the coding sequence, several were found in the 5, putative
promoter region. No polymorphisms consistently and exclusively occurred in VR and not in
changeling and/or black and white Holstein cattle. Common relatives occurred in the pedigrees
of several variant red and changeling cattle. A hypothesis was developed which suggests that a
common mutation is required for the occurrence of either phenotype. A dominant mutation in a
second gene would be required for VR, potentially a promoter mutation in β-defensin300. Two
recessive alleles at a yet unidentified second gene, potentially a promoter mutation in ASIP,
would be required for the changeling phenotype to occur.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-12112008-102654 |
| Date | 12 December 2008 |
| Creators | Dreger, Dayna Lee |
| Contributors | Scoles, Graham, Laarveld, Bernard, Buchanan, Fiona, Plante, Yves, Schmutz, Sheila M. |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-12112008-102654/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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