Hot answers tagged

27

Birds may indeed digest seeds under conditions of rest. It has been postulated that almost all current knowledge on mechanisms of internal seed dispersal has been obtained from experiments with resting animals. A study with the mallard Anas platyrhynchos (common wild duck), claimed to be quantitatively one of the most important seed dispersing animals in ...


16

Lethal genes evolve simply because of random deleterious mutations and absence of strong selection. Recessive lethal genes Random mutations can make a gene product non-functional or reduce its activity. However, in diploid organisms the other fully-functional copy of the gene can compensate for the non-functional allele. Sometimes both the alleles can ...


4

This is just loose terminology. By ‘lethal gene’ Dawkins means an essential gene with a mutation that renders it inactive. With a recessive gene, the one ‘good’ copy in the heterozygote provides enough gene-product to allow survival, in contrast to the situation in the homozygote where the total absence of gene-product is lethal. With a rare mutation, the ...


3

Is there evidence of selection against long proteins and long genes? I am not aware of any such evidence and cursory googling did not reveal studies that researched a correlation between gene selection and gene size. However, the larger a gene, the larger the probability of a deleterious mutation within said gene so I expect that there is some limit to ...


3

Mutations are not performed targeting a specific new phenotype. There is no way an organism can "know" the impact of a specific future mutation anyway. A mutation is just a mistake in the replication process. As a consequence the majority of mutations are deleterious and only a handful of mutations are beneficial. It is true though that the mutation rate ...


2

But cyanobacteria do not seem to use polysaccharides in the same way as plant cells do (building materials, for example) The Calvin-Benson cycle produces glucose which is the starting material for a lot of biosynthetic pathways including that of the nucleotides (ribose from the pentose-phosphate pathway). Glycolytic intermediates are also involved in ...


1

Largely an informed guess based on properties of distributions rather than specific knowledge of statistical genetics: a beta distribution is useful for modeling the frequencies of two alleles at one locus. A Dirichelet distribution, which is a multivariate generalization of a beta distribution, would thus be useful for modeling a set of loci. The flip side ...


1

You can use BLAST or NCBI resources to do an analysis of something like the duplication of a gene in the HIV virus, for example. If you're looking for a place to start, I would recommend just learning the NCBI database resources.


1

Metrics of interest The two metrics you are interested in are $\pi$ - the mean number of differences between two randomly sampled (with replacement) alleles in a population $d$ - the mean number of differences between two randomly sampled (with replacement) alleles coming from two different species Consider two sequences ATCGTCAAT ATAGTTAAT There ...


1

Why do you think that the only benefit from photosynthesis is polysaccharide synthesis? Photosynthesis allows an organism to convert photons into chemical energy. That chemical energy can be stored as polysaccharides and used as a building material, but it can also just be converted into some other compound, or just used to run the organisms metabolism, ...


1

Kostikova et al. 2016. Syst. Biol. developed an algorithm to model trait evolution with inter- and intraspecific variation. The authors use it to show whether a life-history trait (i.e. annual versus perennial) influences the evolution of intraspecific variation in the climatic niches of species While they do not directly incorporate the space ...


1

Another source of developmental noise is due to diffusion. Diffusive processes are stochastic and induce noise in morphogen gradients and results in the concentration as being "jagged". Recent results have directly measured the noise in morphogen gradients of the developing zebrafish. In fact, when you think about the low copy numbers of transcription ...


1

I know of an example in development biology. Here is an example where noise in retinoic acid gradients is required for the boundaries in the developing hindbrain to sharpen. A related result is that the zebrafish hindbrain has a protein to modulate noise, but does not reduce the noise to zero. Together these results show that noise in the retinoic acid ...



Only top voted, non community-wiki answers of a minimum length are eligible