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Category: Genetics (page 4 of 8)

03.29.2013

getting a caffeine fix

Coffee

People aren’t the only organisms that can’t get going without a daily cuppa. Scientists have engineered a strain of E. coli to thrive on caffeine. To engineer this characteristic in the bacteria, the scientists cloned in genetic material from Psuedomonas putida bacteria. This Psuedomonas species was already known to be able to metabolize caffeine. They also needed to clone in another gene from Janthinobacterium in order for the E. coli to completely metabolize the caffeine. After cloning the genetic material into E. coli, they saw that the bacteria’s growth rate was severely limited by the amount of caffeine in their environment and they could tell how much caffeine was present in a drink by how much of the bacteria grew. The scientists are hoping that the bacteria can be used in decaffeinating waterways near major cities, as the water around population centers usually contains lots of caffeine pollution. If you can get access, check out the paper at ACS Synthetic Biology.

03.21.2013

the eerie genetic similarity of giant squid

Giant Squid

The giant squid is one of Nature’s most elusive animals. In fact, the first video of the animal in it’s natural habitat was only captured this January.  Now a new study of the DNA in squids from around the world shows that they are all the same species. The study appears in PNAS. It looks at the DNA from dead squid that had washed ashore around the world and compared the sequences. It turns out that they are all eerily similar. The species has very little genetic diversity. From Scientific American:

When the researchers looked closely at the mitochondrial DNA of the creatures, they noticed something remarkable. Irrespective of where they came from — be it be it California, Japan, South Africa, New Zealand or somewhere else — the squid were genetically very similar.

In fact, the diversity of Architeuthis is lower than that for any other marine animal, except one — the basking shark Cetorhinus maximus, whose current population is thought to have rebounded from a small number of individuals. At first, says Thomas Gilbert, a geneticist at the University of Copenhagen and an author of the study, “When we found that the global genetic diversity of the giant squid was this low, we figured we had made an error.” But then the team checked their numbers again and saw that they were correct.

The findings not only make it clear that all giant squid around the world are the same species, but they also hint that, like the basking shark, the animals came close to extinction at some point in the not too distant past. The results are published inProceedings of the Royal Society B.

03.18.2013

DNA from HeLa cells is sequenced

HeLa cells

HeLa cells viewed under a light microscope

Nature magazine reports that a German lab has sequenced the DNA of HeLa cells. Like cells from most tumors, there are multiple copies of many genes. Excerpt:

Previous work showed that HeLa cells, like many tumors, have bizarre, error-filled genomes, with one or more extra copies of many chromosomes. To get a closer look at these alterations, a team led by Lars Steinmetz, a geneticist at the EuropeanMolecular Biology Laboratory in Heidelberg, Germany, sequenced the popular ‘Kyoto’ version of the cell line and compared the sequence with that of a reference human genome. The team’s results are published in G3.

Steinmetz’s team confirmed that HeLa cells contain one extra version of most chromosomes, with up to five copies of some. Many genes were duplicated even more extensively, with four, five or six copies sometimes present, instead of the usual two.  Furthermore, large segments of chromosome 11 and several other chromosomes were reshuffled like a deck of cards, drastically altering the arrangement of the genes.

Without the genome sequence of Lacks’ healthy cells or that of her original tumor, it is difficult to trace the origin of these alterations. Steinmetz points out that other cervical tumors have massive rearrangements on chromosome 11, so the changes in the HeLa cell may have contributed to Lacks’ tumor.

HeLa cells have been the subject of many biological studies as they are easy to culture and replicate very fast. The cells were originally isolated from an African American woman named Henrietta Lacks, and have been cultured for over 60 years. There is also a fascinating book about the origin of these cells called The Immortal Life of Henrietta Lacks.

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