Scrapie to be Scrapped
Until recently, scrapie, a degenerative disease of the central nervous system of sheep (analogous to mad cow) has spread uninhibited due to minimal knowledge about its transmission. Recent genotyping however, has proved invaluable to monitoring susceptibility.
Normally, PRNP (Prion Protein Gene) produces PrPC, the prion protein molecule. When a mutation arises such that PrPC is misfolded into the infectious form PrPSC, scrapie will develop and can be transmitted to susceptible animals via birth fluids or other infectious tissues. The probability of misfolding lies in the individuals’ DNA and the amino acid sequence of the prion protein.
Scrapie susceptibility is determined by amino acid combinations in codons 136 and 171 of the PRNP molecule, one copy of which is inherited from each parent. These can be as follows:
Normally, PRNP (Prion Protein Gene) produces PrPC, the prion protein molecule. When a mutation arises such that PrPC is misfolded into the infectious form PrPSC, scrapie will develop and can be transmitted to susceptible animals via birth fluids or other infectious tissues. The probability of misfolding lies in the individuals’ DNA and the amino acid sequence of the prion protein.
Scrapie susceptibility is determined by amino acid combinations in codons 136 and 171 of the PRNP molecule, one copy of which is inherited from each parent. These can be as follows:
Codon 136:
- Valine (V)
- Alanine (A)
Codon 171:
- Glutamine (Q)
- Histidine (H)
- Lysine (K). .[H and K are treated as Q as they all have the same susceptibility]
- Arginine (R)
- Histidine (H)
- Lysine (K). .[H and K are treated as Q as they all have the same susceptibility]
- Arginine (R)
Susceptibility as determined by parental genotypes
By selecting breeding stock with AR combinations at codons 136 and 171, even if in only one parents’ genotype, prevalence of scrapie in offspring can be reduced or the disease can be eradicated altogether - easily achieved through this simple and harmless genotyping procedure involving only a sample of the third eyelid. The results…?
- increased productivity
- increased returns
- prevention of unnecessary deaths
→ Countless benefits for all.
So why not utilise this genotyping revolution?
So why not utilise this genotyping revolution?
Michelle Williams
Student No. 41415737
References:
n.d., viewed 22 May 2007, <http://www.animalagriculture.org/scrapie/GenotypingPPT/Spring2007PPT/3%20Genetics%20of%20Scrapie%20March%202007.ppt>
n.d., The Genetics of Scrapie Susceptibility, viewed 20 May 2007 <http://www.aphis.usda.gov/vs/nahps/scrapie/scrapie_genetics.pdf>
Greiner, Scott, June 2002, Genetics of Scrapie, viewed 20 May 2007, < http://www.ext.vt.edu/news/periodicals/livestock/aps-02_06/aps-112.html>
Thomas, L. David, n.d., Genetics of Scrapie Susceptibility in Sheep, viewed 22 May 2007, < http://www.ansci.wisc.edu/Extension-New%20copy/sheep/ETN_01/nov/scrapiegenetics.doc>
