We consider populations that adapt to a sudden environmental change by fixing alleles found at mutation-selection balance. In particular, we calculate probabilities of fixation for previously deleterious alleles, ignoring the input of new mutations. We find that "Haldane's sieve"--the bias against the establishment of recessive beneficial mutations--does not hold under these conditions. Instead...

Dimorphic sex chromosomes create problems. Males of many species, including Drosophila, are heterogametic, with dissimilar X and Y chromosomes. The essential process of dosage compensation modulates the expression of X-linked genes in one sex to maintain a constant ratio of X to autosomal expression. This involves the regulation of hundreds of dissimilar genes whose only shared property is chro...

Although the X chromosome is usually similar to the autosomes in size, gene density and cytogenetic appearance, theoretical models predict that its hemizygosity in males may cause unusual patterns of evolution. The sequencing of several genomes has indeed revealed differences between the X chromosome and the autosomes in the rates of gene divergence, patterns of gene expression and rates of gen...

The dioecious plant Silene latifolia has heteromorphic sex chromosomes, and comparison of the positions of sex-linked genes indicates that at least three large inversions have occurred during the evolution of the Y chromosome. In this article, we describe the isolation of a new sex-linked gene from S. latifolia, which provides new information on the evolution of this plant's young sex chromosom...

N abnormality expressed as irregular growths in the head region of DTOA sophila melanogasfer is under investigation in the genetics laboratory a t the ~JNIVERSITY of UTAH. The experimental evidence indicates that a maternal effect controlled by a sex-linked gene is involved in the expression of the abnormality. In addition to the maternal effect an autosomal gene is required for the exp-ession ...

conclusions albumin gradient method is the enrichment of y-bearing chromosome sperms. separation of spermatozoa by albumin gradient method, introduced by ericsson, is a suitable method for sex selection of male offspring. this technique is safe, because it neither requires toxic materials during sperm separation, nor involves embryo manipulation. objectives the study aimed to assess the separat...

Phototaxis mazes have been employed to select photopositive and photonegative strains of Drosophila simulans. The results suggest that phototactic behavior in D. simulans, as in other Drosophila species, is a polygenic trait. Hybridization using divergent strains revealed that the genes controlling negative phototactic behavior in D. simulans are autosomal, as opposed to D. melanogaster in whic...