1666 TEKS header image

Knowledge and Skills Statement

Science concepts--biological structures, functions, and processes. The student knows that biological structures at multiple levels of organization perform specific functions and processes that affect life.

a type of cell that has a nucleus and other membrane-bound organelles such as the mitochondria or chloroplasts

the reason for which an object or a process occurs in a system

a natural phenomenon marked by gradual changes that lead toward a particular result; a continuing natural or biological activity or function

a type of cell that has no nucleus or major membrane-bound organelles such as the mitochondria or chloroplast

something arranged in a definite pattern of organization; the arrangement of particles or parts in a substance or body; the aggregate of elements of an entity in their relationships to each other

Research

Zaremba-Niedzwiedzka, Katarzyna, Eva F Caceres, Jimmy H Saw, Disa Bäckström, Lina Juzokaite, Emmelyn Vancaester, Kiley W Seitz, Karthik Anantharaman, Piotr Starnawski, Kasper U Kjeldsen, Matthew B Stott, Takuro Nunoura, Jillian F Banfield, Andreas Schramm, Brett J Baker, Anja Spang, and Thijs J G Ettema. "Asgard Archaea Illuminate the Origin of Eukaryotic Cellular Complexity." Nature 541, no. 7637 (January 2017): 353-358. https//:doi.10.1038/nature21031 

Summary:  The origin and cellular complexity of eukaryotes represent a major enigma in biology. Current data support scenarios in which an archaeal host cell and an alphaproteobacterial (mitochondrial) endosymbiont merged, resulting in the first eukaryotic cell. Here we describe the Asgard superphylum, a group of uncultivated archaea that includes Loki-, Thor-, Odin-, and Heimdallarchaeota. Asgard archaea affiliate with eukaryotes in phylogenomic analyses and their genomes are enriched for proteins formerly considered specific to eukaryotes.

Research

Ku, Chuan, Shijulal Nelson-Sathi, Mayo Roettger, Filipa L. Sousa, Peter J. Lockhart, David Bryant, Einat Hazkani-Covo, James O. McInerney, Giddy Landan & William F. Martin. "Endosymbiotic Origin and Differential Loss of Eukaryotic Genes." Nature 524, no. 7566. (2015): 427-432. http://dx.doi.org/10.1038/nature14963

Summary:  Chloroplasts arose from cyanobacteria, and mitochondria arose from proteobacteria. Both organelles have conserved their prokaryotic biochemistry, but their genomes are reduced, and most organelle proteins are encoded in the nucleus. The endosymbiotic theory posits that bacterial genes in eukaryotic genomes entered the eukaryotic lineage via organelle ancestors. Eukaryotic genome sequences, however, increasingly implicate lateral gene transfer, both from prokaryotes to eukaryotes and among eukaryotes, as a source of gene content variation in eukaryotic genomes.