OMIA 000385-9940 : Fecundity, Thoka, FecG(T) in Ovis aries

Possibly relevant human trait(s) and/or gene(s) (MIM number): 601918

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2009

Species-specific description: A segregation analysis of Icelandic sheep by Jonmundsson and Adalsteinsson (1985) provided substantial evidence for a gene of large effect on litter size. These authors named the gene Thoka, after the ewe from which the gene appears to have originated. Heterozygotes give birth to an extra 0.64 lambs, on average. In a segregation analysis of data from a Cheviot flock into which the Thoka gene was introduced via Icelandic rams, Walling et al. (2002) confirmed the existence of a gene of large effect on fecundity, but there was some evidence that this gene was present in the flock before the Icelandic introduction. Since this evidence is only preliminary, the gene will be assumed to be Thoka until further evidence is assembled [FN 13 Jan 2003]

Inheritance: Just as in Fecundity, Cambridge (OMIA 000384-9940), which involves the same gene (GDF9), ewes heterozygous for the Thoka mutation in GDF9 show increased fecundity, but homozygotes for the same mutation are sterile.

Molecular basis: Nicol et al. (2009) identified the causal mutation of Thoka fecundity as "a single base change (A1279C) resulting in a nonconservative amino acid change (S109R) in the C-terminus of the mature GDF9 protein, which is normally expressed in oocytes at all stages of development".

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
GDF9 growth differentiation factor 9 Ovis aries 5 NC_040256.1 (46547527..46544800) GDF9 Homologene, Ensembl, NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Breed(s) Variant Phenotype Gene Allele Type of Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
Cheviot Fecundity, Thoka, FecG(T) GDF9 missense Oar_v3.1 5 g.41841117A>C c.1279A>C p.S427R 2009 19713444 Variant coordinates obtained from or confirmed by EBI's Some Effect Predictor (VEP) tool


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
2013 Juengel, J.L., Davis, G.H., McNatty, K.P. :
Using sheep lines with mutations in single genes to better understand ovarian function. Reproduction 146:R111-23, 2013. Pubmed reference: 23801782. DOI: 10.1530/REP-12-0509.
2009 Nicol, L., Bishop, S.C., Pong-Wong, R., Bendixen, C., Holm, L.E., Rhind, S.M., McNeilly, A.S. :
Homozygosity for a single base-pair mutation in the oocyte-specific GDF9 gene results in sterility in Thoka sheep. Reproduction 138:921-33, 2009. Pubmed reference: 19713444. DOI: 10.1530/REP-09-0193.
2005 Davis, GH. :
Major genes affecting ovulation rate in sheep. Genet Sel Evol 37 Suppl 1:S11-23, 2005. Pubmed reference: 15601592. DOI: 10.1051/gse:2004026.
2004 Davis, GH. :
Fecundity genes in sheep. Anim Reprod Sci 82-83:247-53, 2004. Pubmed reference: 15271457. DOI: 10.1016/j.anireprosci.2004.04.001.
2002 Walling, G.A., Bishop, S.C., Pong-Wong, R., Gittus, G., Russel, A.J.F., Rhind, S.M. :
Detection of a major gene for litter size in Thoka Cheviot sheep using Bayesian segregation analyses Animal Science 75:339-347, 2002.
1997 Russel, A.J.F., Alexieva, S.A., Elston, D.A. :
The effect of the introduction of the thoka gene for fecundity on lamb production from cheviot ewes Animal Science 64:503-507, 1997.
1989 Adalsteinsson, S., Jonmundsson, J.V., Eythorsdottir, E. :
The high fecundity Thoka gene in Icelandic sheep Proceedings of the European Association for Animal Production, 40th Annual Meeting, Dublin, Ireland :, 1989.
1985 Jonmundsson, J.V., Adalsteinsson, S. :
Single genes for fecundity in Icelandic sheep In "Genetics of Reproduction in Sheep", Eds Land RB & Robinson DW. London: Butterworths. :159-168, 1985.

Edit History

  • Created by Frank Nicholas on 06 Sep 2005
  • Changed by Frank Nicholas on 26 Jan 2012