Month: September 2022

HOX CLUSTER. "In arthropods, the first genes in the cluster mediate the expression of the head and associated structures, those in the middle of the cluster control genes that produce legs and wings on appropriate body segments, and so on." https://lnkd.in/dx4KvtT View in LinkedIn

BODY PLAN REGULATORY GENES. "Obviously such sophisticated control systems were not needed in the single-celled ancestors of animals, and thus their evolution is intimately associated with the establishment and initial elaboration of animal body plans." https://lnkd.in/dx4KvtT View in LinkedIn

HOX COMPONENT GENES. "The number of genes in the Hox cluster varies among animal phyla. Sponges, the most primitive of animals, have at least one Hox gene, whereas arthropods have eight. In mammals, the cluster has been repeatedly duplicated to form four clusters, all slightly different, with a total of 38 genes." https://lnkd.in/dx4KvtT View in LinkedIn

VARIABLE HOX PLANS. "It looks very much as if the Hox clusters become larger with increasing body plan complexity, although this cannot be the entire story. Some primitive forms have clusters unlike the Hox cluster of higher forms." https://lnkd.in/dx4KvtT View in LinkedIn

SAME TRIGGERS. "Mammals and arthropods both display a striking diversity of morphologies within each of their body plans, but this diversity is generated chiefly by genes active after the Hox-cluster genes have done their work." https://lnkd.in/dx4KvtT View in LinkedIn

BODY PLAN COMPLEXITY. "Many different body plans can be specified by similar genes early within a cascade, whereas morphological complexity can be achieved by regulatory evolution in many parts of the cascade." https://lnkd.in/dx4KvtT View in LinkedIn

REGULATORY GENE EXPANSION. "What seems clear is that morphological evolution of body plans, such as is documented by Neoproterozoic and Cambrian fossils, involved increases in the complexity of both the body plans and the regulatory systems that specified them." https://lnkd.in/dx4KvtT View in LinkedIn

REGULATORY VS STRUCTURAL GENES. "With each new variation, there is an alteration in the relation between the regulatory genes and the so-called structural genes that actually produce the proteins and eventually the lipids and other building blocks that make up an organism." https://lnkd.in/dx4KvtT View in LinkedIn

SO ENDS this contemplation of the confounding Cambrian explosion. Next weekend we consider the Great Unconformity, a period directly before the Cambrian when geologist believe that 3-5 vertical (yes, vertical) kilometers of the earth’s surface globally was erased. This could explain the missing fossil record and make the Cambrian explosion an optical illusion. Explaining the Cambrian has certainly stretched all story-telling skills. View in LinkedIn

CUMULATIVE CULTURE. "Our culture is cumulative because we are born into highly constructed environments full of amazing gadgets like language and literacy." https://lnkd.in/dwNsDzt View in LinkedIn