Genetics & Molecular Biology

Trichoplax adhaerens is a bizarre little animal with a decidedly simple morphology. (You can see some here). There has been some question as to the relationship between this critter and other animal groups, but mitochondrial sequences (Dellaporta et al. 2006) and, as of this week, a complete nuclear genome sequence (Srivastava et al.
This appeared in my weekly automated journal search. I have ordered the paper as I can't find an online copy, but the abstract pretty much covers what the argument will be. Same old pre-1980s adaptationist idea presented as radically novel.
Mallik, M. and Lakhotia, S.C. 2008. Noncoding DNA is not "junk" but a necessity for origin and evolution of biological complexity. Proceedings of the Indian National Science Academy Section B - Biological Sciences 77 (Sp. Iss.): 43-50. All eukaryotic genomes contain, besides the coding information for amino acids in different proteins, a significant amount of noncoding sequences, which may or may not be transcribed.
A study of 228 women has revealed genetic variants responsible for body shape, according to research published in BMC Genetics.

Based on work in the fruit fly Drosophila melanogaster, the study identifies natural variation in the human LAMA5 gene as a key determinant of weight.

As the prevalence of obesity and related health problems continues to increase worldwide, there is considerable effort being devoted to identify genetic mechanisms that control fat storage. Maria De Luca led a team from the University of Alabama at Birmingham, USA, who identified candidate genes using different strains of Drosophila.

A paper in Cell is reporting the sequence of a Neanderthal mitochondrial DNA genome. Mitochondrial DNA, which you inherit only from your mother, has long been among the most useful DNA regions for tracing your ancestry. In the Neanderthal mitochondrial genome, researchers found, not surprisingly, that the sequence differences are well beyond the range of what we see within human populations, meaning that Neanderthals clearly were a distinct biological sub-species.
Part 1 on The Plausibility of Life

Darwin is famous for convincingly arguing that natural selection can explain why living things have features that are well-matched to the environment they live in. In the popular consciousness, evolution is often thought of as natural selection acting on random mutations to produce the amazing tricks and traits found in the living world. But “random mutation” isn’t quite right - when we describe evolution like this, we pass over a key problem that Darwin was unable to solve, a problem which today is one of the most important questions in biology. This key problem is the issue of variation, which is what biologists really mean when they talk about natural selection acting on random mutations. Variation and mutation are not the same thing, but they are connected. How they are connected is the most important issue covered Kirschner and Gerhart’s The Plausbility of Life. It is an issue Darwin recognized, but couldn’t solve in those days before genetics really took off as a science.

Natural selection really works on organisms, not directly on mutations: a particular cheetah survives better than other cheetahs because it can run faster, not because it has a DNA base ‘G’ in a particular muscle gene. A domesticated yeast can survive in wine barrel because of how it metabolizes sugar, not because of the DNA sequence of a metabolism gene. I know what you’re thinking: this is just a semantic game over proximal causes. But this is not just semantics, it is a real scientific problem: what is the causal chain that leads from genotype to phenotype, that is, from an individual organism’s DNA sequence, mutations included, to the actual physical or physiological traits of the complete organism?

Sleep is regulated by two processes: circadian and homeostatic. Circadian regulation affects the timing of sleep, and the homeostatic mechanism affects the need for sleep.

While scientists and physicians know what happens if you don't get six to eight hours of sleep per night, investigators have long been puzzled about what controls the actual need for sleep. Researchers at the University of Pennsylvania School of Medicine might have an answer, at least in fruit flies. In a recent study of fruit flies, they identified a gene that controls sleep.

The white horse has been an icon for dignity, purity and good guys across various human cultures all over the world but only now has an international team been able to identify the mutation that causes this fascinating trait.

Their analysis shows that white horses carry an identical mutation that can be traced back to a common ancestor that lived thousands of years ago. The study is interesting for medical research since this mutation also enhance the risk for melanoma.

The great majority of white horses carry the dominant mutation 'Greying with age.' A Grey horse is born colored (black, brown or chestnut) but the greying process starts already during its first year and they are normally completely white by six to eight years of age, though the skin remains pigmented. Thus, the process resembles greying in humans but the process is ultrafast in these horses. The research presented now demonstrates that all Grey horses carry exactly the same mutation which must have been inherited from a common ancestor that lived thousands of years ago.


“If you want to be happy for the rest of your life you need to make an ugly woman your wife,” or “if your rent is late and you might have to litigate, don’t worry, be happy,” are a few of the ways some popular singers verbalize ways to stay happy. The role that genes and environment play on happiness and the choices a person makes in life have been regularly investigated in studies involving criminals and twins.


Common genetic variations affecting nicotine receptors in the nervous system can significantly increase the chance that European Americans who begin smoking by age 17 will struggle with lifelong nicotine addiction, according to researchers at the University of Utah and their colleagues at University of Wisconsin-Madison.

The study highlights the importance of public health efforts to reduce the number of youth who begin smoking.

These common gene variations - single nucleotide polymorphisms (SNPs) - are changes in a single unit of DNA. SNPs that are linked and inherited together are called a haplotype. The researchers found that one haplotype for the nicotine receptor put European American smokers at greater risk of heavy nicotine dependence as adults, but only if they began daily smoking before the age of 17. A second haplotype actually reduced the risk of adult heavy nicotine dependence for people who began smoking in their youth.

One of the many aggravations I encounter when reviewing manuscripts is that some authors greatly overstate the applicability of statistically significant patterns they report. For example, a statistically significant pattern in a small comparison of a few animals may be extrapolated in the discussion to the kingdom at large.

Today I was disappointed to see a paper that is soon to come out in Zoology that does the opposite -- i.e. takes a non-significant relationship in a handful of species and pretends that it challenges the importance of broad relationships that have been considered important for decades.

The paper in question is: