Delayed activation of the paternal genome during seed development

Article Abstract:

The activity of many genes acting during early embryo and endosperm formation could depend entirely on transcription from the maternally inherited allele. It was found that none of the paternally inherited alleles of 20 loci tested is expressed during early seed development in Arabidopsis. For genes expressed at later stages, the paternally inherited allele becomes active three to four days following fertilization. It seems that the first few days of enbryogenesis and endosperm development are mainly, if not entirely, under maternal control.

Seeds

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A GTP-exchange factor required for cell orientation

Article Abstract:

It has been possible to identify cdc24 alleles that do not have an impact on vegetative growth but significantly reduce the ability of yeast cells to mate. The mutants are specifically defective in the binding of Cdc24 to the G-protein beta-gamma subunit. This indicates a model in which binding of Cdc24 to G-beta-gamma results in recruitment to the area of the receptor or in activation of Cdc24. This local concentration of activated Cdc24 is needed for oriented growth towards a pheromone gradient.

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Neutrality or selection?

Article Abstract:

A bi-allelic selection model which does not impact genetic change is proposed where both alleles are present in equal numbers. The model supports a neutral equilibrium and provides a minimum mean fitness and a maximum excess of heterozygotes. Data from three generations of genetic crosses using the human major histocompatibility complex loci HLA-A and HLA-B in South Amerindians support this conclusion.

Models, Natural selection, Genetic research

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