Year: 2022

MEIOSIS is needed to keep the chromosome number the same in diploid sexual creatures from one generation to the next. https://lnkd.in/dGqaW47 View in LinkedIn

DIPLOID FORM. “For most plants and all animals, the majority of life is spent in diploid form. During sexual reproduction, haploid gametes are formed via meiosis and then come together during fertilization.  Some simpler Eukaryota spend most of their life cycle in diploid form.” https://lnkd.in/dTisCwg View in LinkedIn

"MEIOSIS is the type of cell division that gives rise to eggs and sperm." Versus mitosis which occurs during normal development and growth and does not alter the chromosome number. https://lnkd.in/dt3vnRH View in LinkedIn

FRAGMENT FROM NATURE concludes this weekend on the theme of competition and resource allocation. At all levels of living creatures, from different species in ecosystems — from identical populations, from individual organs, from the cells within the body, from the ecosystem of organelles in cells, to the very genes — there is evidence of competition for key limited resources. These nested hierarchies of communities of living parts all appear to play out a dance between natural selection versus preferential resource allocation. View in LinkedIn

REGENERATION MEMORY. "When the limb of a salamander, or the liver of a mouse, is partially amputated, the remainder regenerates to its normal size and shape even though the context in which this regeneration occurs is very different from that in which the structure developed initially." http://www.pnas.org/content/95/7/3685.full View in LinkedIn

EXTERNAL REGULATORS. "It is clear that these trait-autonomous processes are also regulated at a higher level. In insects, developmental hormones such as the ecdysteroids and JHs and external factors such as starvation and extreme temperatures are known to affect whole-animal growth and thus also the final sizes of traits." (JH = juvenile hormone). http://www.pnas.org/content/95/7/3685.full View in LinkedIn

THIRD REGULATION. "Herein we illustrate a third and intermediate level of size regulation, manifest as what appears to be competition among growing traits within late-stage larvae immediately prior to pupation. Superficially, at least, the mechanism of trait competition described herein is similar to the process of cell competition and compensatory growth that operates within compartments of individual imaginal discs." http://www.pnas.org/content/95/7/3685.full View in LinkedIn

EITHER-OR. "Increased growth of one trait occurs at the expense of growth in other traits, without overall changes in the size of the animal, much as faster-growing cells (e.g., minute+ cells expressed in a minute− background) out-compete neighboring cells for space within a growing imaginal disc without affecting the final size of the disc." http://www.pnas.org/content/95/7/3685.full View in LinkedIn

TRAIT SPECIFIC. "It is significant that the allocation tradeoff is not diffuse or generalized but is concentrated on only one or a few traits. There are several possible developmental mechanisms that could explain the preferential allocation of excess resources to certain tissues and not to others." http://www.pnas.org/content/95/7/3685.full View in LinkedIn

SPATIAL OPTION. "It is possible that allocation is compartmentalized so that tissues that are physically close to the site of loss receive a disproportionate to amount of the excess resource." http://www.pnas.org/content/95/7/3685.full View in LinkedIn