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UW-Madison ANSCI 361 - From Phenotype to Genotype: Major genes affecting ovulation rate in sheep

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An Sci 361 1st Edition Lecture 7 Outline of Last Lecture I. Gene disordersa. Singlei. Typesii. Causesb. PolygenicII. Citrullinaemiaa. Humansi. Type Iii. Type IIb. Cattlei. CausesIII. ASS DeficiencyOutline of Current Lecture I. Fertility Genesa. Booroola Geneb. Other genesII. Major Sheep Genesa. BMP-15i. Mutationsb. GDF9c. BMPR-IBi. MutationsCurrent LectureWhat are the fertility genes?• Genetics accounts for one third of the decline in pregnancy rate (Shook 2006)• Many quantitative trait loci (QTL) reported for fertility traits• Why is it challenging to identify fertility genes?• Low heritability for most fertility traits?These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Inaccurate phenotypes collected in the field?• Different phenotypic measures in different studies? Booroola Gene:• Also called FecB for fecundity• The Booroola Merino sheep was named after the property ‘Booroola’, located at Cooma in New South Wales, Australia.• Brothers Jack and Dick Seears identified a line of highly prolific Merinos ascending from a ewe in the main flock that had triplets.• Ewes with one copy of the gene produce 1.6 extra eggs and give birth to 1.0 extra lamb • Booroola gene in Australia can be traced back to Bengal sheep (Garole) which were imported from Calcutta in 1792/3 and crossed with Merinos.Major genes affecting ovulation rate in sheep:• In 1980, Piper and Bindon: ovulation rate in Booroola Merino is affected by a single major gene! • Ovulation rate is a complex trait!• Breakthrough in 2001: Mulsant et al. (PNAS); Souza et al. (J. Endocrinol); Wilson et al. (Biol. Reprod.): the inheritance of prolificacy in Booroola Merinos was the result of a mutation in the bone morphogenetic protein 1B receptor (BMPR-1B).• Major gene: the difference between the homozygotes is at least 0.5 standard deviations.• For ovulation rate: +1.6 ova per copy of FecB alleleCommercial DNA test developed in 2002:-Sequence BMPR1B gene from Booroola and non-Booroola sheep-Found SNP at base 830; causes amino acid changefrom glutamine to arginine-Homozygotes produced ~3.0 extra eggs (1.5 extra lambs)-This discovery makes it possible to use DNA testing to characterize carriers of the mutation PCR-RFLP:PCR: amplify segment including polymorphic siteDigest PCR product with restriction enzyme110 bp fragment = Booroola allele140 bp fragment = wild type alleleMajor Genes in Sheep:-Found in study of highly prolific sheep from Romney breed in New Zealand-Evidence for X-linked major gene in family of a highly prolific eweInverdale gene or FecXI+0.8 ova for one copy of FecXI allele2 copies – ovarianHypoplasia (smaller than normal)BMP-15 Mutations:• Several mutations found • FecX(I): Inverdale allele increases litter size by about 0.6 lams per ewe lambing.• FecX(H): Hanna allele increases litter size by 0.6 lambs per lambing• FecX(H) mutation causes premature stop codon• Two different mutations, but have similar phenotypes• Homozygotes II, HH, and heterozygotes HI are infertile in a dosage-sensitive manner.GDF9:-Found in study of highly prolific sheep breeds in Ireland (Cambridge and Belclare)-GDF9 considered as candidate gene+2 ova for one copy of FecGH allele2 copies – ovarian hypoplasia-GDF9 (growth and differentiation factor 9) -Member of TGF-ß gene family-Expressed in oocyte-One copy of the mutation FecGH increases ovulation rate by 1.4-GDF9 knockout mice infertile due to blocked follicular developmentMutations in BMPR-IB and BMP-15 genes are associated with litter size in Small Tailed Han sheep (Ovis aries) Chu et al. 2007:Objectives:1. Detect SNPs in BMPR-IB and BMP15 by RFLP and sequencing2. Investigate the combined effect of the 2 genes on prolificacy of Small Tailed Han sheepMethods:Collection of blood and litter size from 188 ewesBMPRP-IB: genotyping of exon 6 SNP by PCR-RFLP using Ava II BMP15: genotyping a SNP by PCR-RFLP using Hinf I restriction


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