Month: September 2022

EVENT COUNTER MINIMA. “An intracellular counting mechanism must be present. These data included: 1) the Phase III Phenomenon itself; 2) our observation that cryogenically preserved cells "remember" at what doubling level they were preserved; and 3) the enormous literature describing hundreds of biological changes occurring in normal cells well before they lose their replicative capacity.” http://protein.bio.msu.ru/biokhimiya/contents/v62/full/62111380.html View in LinkedIn

NUCLEAR REPLICOMETER. “In early efforts to determine the location of the replicometer, early experiments in which the nuclei of old and young cultured cells were fused to the enucleated cytoplasm of opposite aged cytoplasts revealed that the replicometer was located in the nucleus.” http://protein.bio.msu.ru/biokhimiya/contents/v62/full/62111380.html View in LinkedIn

FRAGMENT FROM NATURE these next two weekends deal with plants as alien creatures with confoundingly complex life styles, such as alternation of generations. Plants asexually make spores, which are single haploid cells (one set of chromosomes, n) that can make another plant when stuck in the ground. They also use sperm and egg to reproduce. But the two are linked: the sexual plant makes an asexual plant (n), and that in turn completes the cycle by making the sexual plant (2n), and each event makes a new generation, by alternating sexual and asexual reproduction. Weird. View in LinkedIn

VERY STRANGE SYSTEM. "Imagine if you looked exactly like your grandmother but nothing at all like your mother. In fact, your mother would only have half of the genetic information that you have. While this seems very unrealistic, it's actually how many plants reproduce by using an alternating life cycle." https://lnkd.in/dUu-njs View in LinkedIn

VERY VARIED SYSTEM. "Some plants have only one type of sporophyte, but two types of gametophytes (essentially male and female gametophytes; the male only produces sperm, the female only produces eggs). Other plants have male and female sporophytes as well (male sporophyte only produces spores that create male gametophytes, and so on). Some plants can have just one type of sporophyte and just one type of gametophyte (in this case the single gametophyte produces both eggs and sperm)." https://lnkd.in/dDq6NXv View in LinkedIn

LAND PLANT CHARACTERISTICS. #1. "The embryophytes are unique among all extant lineages in possessing three important and interrelated reproductive attributes. First, they possess a sexual life cycle that requires an alternation between a multicellular haploid generation, which produces sperm and egg cells (the gametophyte), and a multicellular diploid generation, which produces meiospores with sporopollenin-rich walls (the sporophyte)." https://lnkd.in/dcZcdNY View in LinkedIn

LAND PLANT CHARACTERISTICS. #2. "Second, they develop multicellular, parenchymatous structures that produce eggs and sperm (called archegonia and antheridia, respectively)." http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2009.03054.x/full View in LinkedIn

LAND PLANT CHARACTERISTICS. #3. "Third, they retain the fertilized egg (i.e. the zygote) within the archegonium, wherein the sporophyte embryo is nurtured and protected. The retention of the diploid embryo within the archegonium is the reason why the land plants are called ‘embryophytes’ and why the older literature referred to them as the Archegoniatae." http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2009.03054.x/full View in LinkedIn

SOMA VS GERMLINE SEGREGATION. "Plants undergo alternation of generation in which reproductive cells develop in the plant body (“sporophytic generation”) and then differentiate into a multicellular gamete-forming “gametophytic generation.” http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn

MAIN BODY FORM. "Plants alternate between two generations—one haploid and the other diploid. In flowering plants, the main plant body forms the “sporophytic” generation, within which highly reduced male and female “gametophyic” generations develop." There are exceptions such as bryophytes (mosses, liverworts, and hornworts), where the gametophyte is the main body form, or ferns where the sporophyte is the main form. http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn