RESUMO
World-wide reports of amphibian population declines have led to increased interest in the reproductive biology of anurans. As a model system, here we present evidence for the effective cryoprotection of sperm from the Puerto Rican frog, Eleutherodactylus coqui, using mixtures of fetal bovine serum (FBS) and dimethylsulfoxide (Me(2)SO), glycerol or sucrose extenders. Using a fluorescent dye exclusion assay, we found that 53.9 and 50.4% of all sperm with intact membranes prior to freezing maintained membrane integrity after rapid freezing and thawing when protected with either a FBS/glycerol or FBS/sucrose solution, respectively. The methods reported here may be useful for similar work with many of the more than 700 other species in this genus.
Assuntos
Criopreservação/métodos , Preservação do Sêmen/métodos , Espermatozoides , Animais , Anuros , Permeabilidade da Membrana Celular , Crioprotetores , Corantes Fluorescentes , Técnicas In Vitro , Masculino , Porto Rico , Soluções , Motilidade dos Espermatozoides , Espermatozoides/fisiologiaRESUMO
Ancestry informative markers (AIMs) are genetic loci showing alleles with large frequency differences between populations. AIMs can be used to estimate biogeographical ancestry at the level of the population, subgroup (e.g. cases and controls) and individual. Ancestry estimates at both the subgroup and individual level can be directly instructive regarding the genetics of the phenotypes that differ qualitatively or in frequency between populations. These estimates can provide a compelling foundation for the use of admixture mapping (AM) methods to identify the genes underlying these traits. We present details of a panel of 34 AIMs and demonstrate how such studies can proceed, by using skin pigmentation as a model phenotype. We have genotyped these markers in two population samples with primarily African ancestry, viz. African Americans from Washington D.C. and an African Caribbean sample from Britain, and in a sample of European Americans from Pennsylvania. In the two African population samples, we observed significant correlations between estimates of individual ancestry and skin pigmentation as measured by reflectometry (R(2)=0.21, P<0.0001 for the African-American sample and R(2)=0.16, P<0.0001 for the British African-Caribbean sample). These correlations confirm the validity of the ancestry estimates and also indicate the high level of population structure related to admixture, a level that characterizes these populations and that is detectable by using other tests to identify genetic structure. We have also applied two methods of admixture mapping to test for the effects of three candidate genes (TYR, OCA2, MC1R) on pigmentation. We show that TYR and OCA2 have measurable effects on skin pigmentation differences between the west African and west European parental populations. This work indicates that it is possible to estimate the individual ancestry of a person based on DNA analysis with a reasonable number of well-defined genetic markers. The implications and applications of ancestry estimates in biomedical research are discussed.