Choosing negative control of cell division: one of the major cause of problems in animal system

Some weeks back when we were discussing about cell division and cancer we were comparing plant vs animal cell cycle and the interesting question came is “Why animals and plants chose different mode of controlling their cell division ?”.  I thought of sharing this with you in this post.
Plants normally do not die (premature death) out of inherent problems (defects in their own genes controlling cell cycle). Mostly their premature death is due to pathogens or stress which are external. In contrast, in animals including human one of the major cause of premature death is the cancer which is due to the defects in cell division control genes.  If we take an aerial view of this problem one thing is clear that plant cells are

Tomato is tomato because of two whole genome triplications

Tomato Genome Update - 2

Analysis of the recently sequence tomato genome in comparison to potato and grape genome reveal that massive genome duplication events shaped the evolution of these plants. Ancestors of tomato genome underwent whole genome triplication twice, one very early in a common eudicot ancestor shared with rosid and the second more recent triplication in the ancestor of tomato and potato followed by widespread gene loss. This recent  triplication has occurred around  71 million years ago well before divergence of tomato and potato which took place approximately

Segmental genome duplication responsible for our brain power

Genome duplication is the trigger for evolution. Complex multicellular organisms have evolved from simple unicellular organisms by genome duplication and other genome rearrangements. Genome duplication can be of two types: whole genome duplication in which a diploid organism becomes a tetraploid and provide whole set of additional genes i.e for every old gene a new copy is provided. This type of change is considered to be responsible for major changes in organisms including speciation. The second type of duplication is called segmental duplication or copy number variation.  Here only a part of the genome gets duplicated and provide additional copies of only those genes in the duplicated regions. This type of  variation is considered to be responsible for differences among closely related organisms for example between monkeys and humans. Immediately after sequencing genomes of chimp and other primates Scientists were expecting to find a segmental duplication of  genomic regions possessing genes associated with  the brain i.e neural system but were not successful.

Recently  two  groups of Scientists led by Evan Eichler and Franck Polleux have found a part of the missing clue.  They identified segmental duplication that led to

Two Human Ancestor Species Co-Existed

A fossil discovered in Ethiopia suggests that humans' prehistoric relatives may have lived in the trees for a million years longer than was previously thought.
The find may be our first glimpse of a separate, extinct, branch of the human family, collectively called hominins. It also hints that there may have been several evolutionary paths leading to feet adapted for walking upright.
The fossil, a partial foot, was found in 3.4-million-year-old rocks at Woranso-Mille in the Afar region of Ethiopia. Bones of the hominin Australopithecus afarensis — the species to which the famous 'Lucy' skeleton belongs — have also been found in this location and from the same period.

Au. afarensis has a big toe that is more closely aligned with the other digits on the foot, an adaptation that provides support during upright walking. Au. afarensis “was fully bipedal and had already abandoned life in the trees”, says study author Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio, whereas the newly discovered creature had not seemingly committed to life on the ground.But unlike Au. afarensis, the latest find has an opposable big toe — rather like a thumb
 on the foot — that would have allowed the species to grasp branches while climbing. Modern apes have similar toes, but the youngest hominin previously known to have them is Ardipithecus ramidus, which lived about 4.4 million years ago. The details of the discovery are published today in Nature1.
Other features of the fossil foot show that it did not belong to an ape, but that it is truly a member of the hominins, says Haile-Selassie. The latest specimen is “very much like the Ardipithecus foot, which I believe had many hominin features, so it’s likely to be a hominin”, agrees Daniel Lieberman, an anthropologist at Harvard University in Cambridge, Massachusetts, who was not involved in the study.
Good grasp of history
The discovery shows that one hominin lineage had grasping feet for at least a million years after Ar. ramidus. The creature was probably more agile in the trees than Au. afarensis but less nimble on two feet, says William Harcourt-Smith, an anthropologist at the City University of New York’s Lehman College. “We can only get a tantalizing glimpse at this, but its bipedal gait is likely to have been very different from Lucy’s and was probably a lot less efficient,” he says.
The finding will force a rethink regarding the course of early hominin evolution, Harcourt-Smith adds. The addition of a mystery hominin species at this crucial time period suggests that the new species' lineage split from that leading to Lucy earlier in hominin history, and provides further evidence against the idea that modern humans evolved via a linear progression of species from apes. “This [finding] is fascinating, and makes the evolution of this defining behaviour not a single, linear evolutionary event, but a far more complex affair,” Harcourt-Smith says.

Link to Nature Paper  

doi:10.1038/nature.2012.10342

 

The Burtele partial foot (BRT-VP-2/73). A laboratory photo after cleaning and preparation. It is shown here in its anatomically articulated form.
© The Cleveland Museum of Natural History