background: we describe karyotypic variations and the in vitro methods for plant propagation and conservation as well as detailed chromosomal analysis of (aloe vera l.) and aloe littoralis from iran during flowering stage. objectives: this karyotypic was discovered because of a difference in the position of the chromosome and due to genomic differentiation in domesticated populations of the ira...

One of the stronger empirical generalizations to emerge from the study of genetic systems is that achiasmate meiosis, which has evolved 25-30 times, is always restricted to the heterogametic sex in dioecious species. usually the male. Here we collate data on quantitative sex differences in chiasma frequency from 54 species (4 hermaphroditic flatworms, 18 dioecious insects and vertebrates and 32...

MSH4, a meiosis-specific member of the MutS-homolog family of genes, is required for normal levels of recombination and fertility in budding yeast, mouse, and Caenorhabditis elegans. In this paper, we report the identification and characterization of the Arabidopsis homolog of MSH4 (AtMSH4). We demonstrate that AtMSH4 expression can only be detected in floral tissues, consistent with a role in ...

In juvenile Xenopus retinotopic fibre order in the optic tract near the chiasma was investigated by labelling small groups of optic fibres from peripheral retina with HRP. This selective fibre labelling with HRP was combined with autoradiography following administration of tritiated thymidine to the eye, so that the HRP-labelled fibres could be located within the borders of the optic tract. Fib...

It is often convenient to define models for the process of chiasma formation at meiosis as stationary renewal models. However, count-location models are also useful, particularly to capture the biological requirement of at least one chiasma per chromosome. The Sturt model and truncated Poisson model are both count-location models with this feature. We show that the truncated Poisson model can a...