J Appl Physiol. Seasonal variation in Y-chromosomal haplotype frequencies among calves in relation to period of conception. Conception dates of the calves were estimated on the basis of the midpoint age per age cohort i. Foetus sex was determined using external genitalia characteristics.
In the well-known X-Y system of mammals, individuals inheriting a Y chromosome become males, and XX individuals become females.
They mapped the genes relative to the PAR and compared the nucleotide sequences of the X and Y version of each gene in each species. Their discovery required sophisticated crossing schemes, often between individuals from different populations or model of sex chromosome evolution performance in Bury species [ 7 ].
The authors also report evidence for some degeneration of the Silene Y chromosome genes. It is difficult to envisage a physiological mechanism capable of making haplotype so successful under stressful conditions dry periodsyet so unsuccessful under beneficial conditions wet periods.
Metrics details.
Characterization of life history traits in wild-derived laboratory strains of turquoise killifish revealed that while different populations have similar rates of sexual maturation Blazek,populations from arid regions exhibit the shortest lifespans, while populations from more semi-arid regions exhibit longer lifespans Blazek, ; Terzibasi et al.
For A. Hence, dry populations have overall smaller genetic diversity than populations from less dry regions. Evolution of postmating reproductive isolation: the composite nature of Haldane's rule and its genetic bases.
First, there is strong purifying selection acting at the protein level in both species. The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes.
From onwards, culling of African buffalo has been used in KNP as a population management and disease monitoring tool [ 27 , 54 ]. In the case of mammals, whose sex chromosomes evolved about million years ago, loss of recombination led to widely diverged X and Y chromosomes that pair only over a very small region, the pseudoautosomal region PAR; because in this region the X and Y still behave like autosomes.
Randomisation-based tests for genetic differentiation with , repetitions and no pooling of haplotypes were performed using FSTAT 2.