Tag Info

Hot answers tagged

10

I think the issue with Intelligent Design is not so much that its patently proven wrong. On the contrary, the problem is that it not a scientific hypothesis and so it really isn't a scientific question. If I may, the basis of the scientific method, as formulated by Karl Popper, but commonly in use today, is that science is the putting forth of theories ...


9

You have clearly given this a lot of thought, unfortunately, as @adam.r said, you are laboring under certain misapprehensions. The quick answer is that each generation does not "improve" on the last. That is a common misconception. In a bit more detail: First of all, your copying metaphor is a bad one. There was no "perfect original", I expand on this ...


8

This question is closely related, and the fascinating link posted by @JohnSmith is a good read. In short, with a four-base system, and a codon size of 1, you get four possible amino acids. Silly system. A codon size of 2 gives 16. Not too shabby, but not a lot of room for growth, and not enough for those 20 amino acids. Codons of size 3 gives 64 - ...


6

The smallest unit that can be selected is, of course, the single nucleotide. The most striking examples of this are Single Nucleotide Polymorphisms (SNPs), many of which confer selective (dis)advantages. To take a simple example, imagine a SNP that introduces a frameshift mutation, rendering a gene incapable of producing its protein. If that protein is ...


4

We know about nuclear DNA having a mitochondrial origin mainly in two ways: (1) a sequence in the nucleus is found to closely match a sequence found in mitochondria, or (2) mitochondrial proteins are found to be encoded by the nuclear genome but not by the mitochondrial genome, and those proteins seem likely to have been necessary for sustaining life of the ...


4

Interesting question. I researched this a bit now and the phenomenon is termed "numt" for "nuclear mitochondrial DNA". This term descrives the transfer of cytoplasmic mitochondrial DNA sequences into the separate nuclear genome of a eukaryotic organism. It seems that most of these sequences are inactive. This list at pseudogene.net has a large number of ...


3

Even when you can live without Histone H1, its a widely distributed protein which you find in basically all living cells (except for some yeasts if I remember correct). This points to the fact that it must be available for quite a while. The same is true for the catalytic subunit of the DNA polymerase. Somatropin is still pretty important (and can be found ...


3

You either want a introductory book in evolutionary biology or a book that provide models/formulations of evolutionary processes In my first class of evolutionary biology I had this textbook: Futuyama, Evolution I think it gives a good start to the field and offers a good overview of the difference subfields. If you think you already knows enough about the ...


3

There are both chemical and electrical synapses in many organisms. The electrical synapses are called gap junctions. As you point out, the primary advantage of gap junctions is their speed, and they are commonly used in systems involving defensive reflexes. However, as AndroidPenguin indicates, chemical synapses allow for greater computational abilities ...


3

This is the coolest part. Those synapses are the reason the brain is so complex! Basically you've got the first part right, the neurones are quicker and they transmit messages from one end to the other. The other thing you have to do is analyse and calculate. Signals from multiple neurones feed into a single neurone using a chemical synapse. Similarly the ...


3

I would recommend The selfish gene by Richard Dawkins. It is targeted at a scientifically interested audience, but well written and recognized by the scientific community. http://amzn.com/0199291152


2

I think this book (The Story of Life, Southwood) would be just what you are looking for - it was one of my modules during my undergrad in Evolution and I think it touches on the basic geology too. It is quite an easy ready but covers the material pretty well, it also has good reviews on Amazon etc.


2

If sufficient time has elapsed, there will be a large number of transversions present between the original base and the final state. The initial state will therefore not matter. Say, you flip (turn over, not toss) a coin at random intervals. For short time and few flips, the initial state will matter. But if you go on flipping it for millenia, the final ...


2

When lactose is present in a cell, some of it is enzymatically converted by $\beta$-galactosidase from the $\beta(1,4)$ linkage (typical of lactose) to the $\beta(1,6)$ glycosidic linkage (becoming allolactose). Allolactose and other analogues can then bind LacI to induce the appropriate conformational change and unbind the lac operator (one such review ...


2

Everybody said it already, but there is none. The original HWE equation ($(p+q)^2=1$) works because you've got two variables and two equations ($p+q=1$) to work with (in reality, these are just one equation and one variable, since $q=1-p$ so $p+(1-p))^2=1$). Now you have three variables and still only the one equation ($p+q+r=1$) which is, mathematically, ...


2

I’ll add a slightly different perspective, although terdon’s answer already contains the relevant facts. The thing that makes DNA endure in the face of imperfect copying is that, like computer storage, it’s digital. The relevant property of digital data here is that individual pieces of information aren’t given on a scale, they’re drawn from a strongly ...


2

Some elements of response to your question. First, something about tRNA frequency. Even if there are six codons for a given amino acid, they are not equivalent because some will correspond to abundant tRNA, while others correspond to very minor tRNA. This has significant influence on the traduction speed, as the traduction will dramatically slow down on ...


2

Really interesting question. I am not sure, if the mutation rate is something "actively done" by the virus. I think its more a byproduct of vast replication after taking over the host cell. Mutations with a negative effect are deleted, those with neutral effects will be there, and those with positive mutations will be selected for. This paper looks ...


2

The expression $f = 2h-1,$ coefficient of inbreeding (COI) is a measure of homozygosity. Since in a randomly breeding herd (of cattle) we expect 50 per cent heterozygous and 50 per cent homozygous, the minimum for $2h-1 $ is 0. If the cattle's genome is purely homozygous (aa, AA) we have $2h-1 = 1.$ (h is total homozygosity--see Wright's paper, linked ...


2

It may also be called as Idea of maximum parsimony. It is used in phylogenetics to construct phylogenetic trees which require the least number of evolutionary events.


1

Heterochromatin profile is of course different in different cells but I am not sure if absolute heterochromatin content will vary greatly. This DNAse hypersensitivity region data is for human cells but same principles apply to all organisms. If I have to take a guess then I would say that quiescent cells are likely to have more heterochromatin. ...


1

The principle of least effort / path of least resistance fit pretty well: animals, people, and systems (like evolution or a mechanical system like a machine) will naturally choose the path of least resistance or effort. The principal applies to chemistry (low energy states) and physics (the path an electrical current takes) as well. Occam's Razor fits ...


1

I really good intro to evolution book is The Evolution of Vertebrate Design by Leonard Radinski. Also, for a more math based approach you could look into Narrow Roads of Gene Land. These are collected papers of W.D Hamilton.


1

This is actually a very interesting yet difficult question to give a single precise answer to. I will try and summarize for you a "meta answer": Complexity Science Some consider complexity not to be a Biological topic as such, since it is a property that accumulates in non-biological systems e.g. economics, technology, music, language - in fact anything ...


1

There are indeed 'gap junctions' which pass current directly from one cell to the next. So what advantages do we get out of chemical synapses that gap junctions do not provide? Asymmetry. Synapses to not operate in reverse, thus the postsynaptic cell cannot generate currents in the presynaptic terminal (although there are secondary forms of communication ...



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