Is it true that genes don't disappear over evolution process?

Question

Is it true that we have all of our ancestors genes (from the first bacteria)? I've also heard that human embrio grow tails then reabsorb it later, and that there are few whales that were found posessing hind legs (possibly from abnormal reactivation of their ancestor's genes).

Answer 1

There was a very big story few years back in the media which called a dolphin which had been found with a extra pair of flippers, resembling the species some 40 million years ago as an evolutionary throwback.

Other various other similar examples include, as you mentioned a whale in 1919 found with 1-metre-long hind leg-like appendages with a full set of bones.

This all contradicts what is known as Dollo's law, which states evolution cannot, or has a vanishingly small chance of, running backwards.

Evolution functions of course mainly through copying errors when making offspring. This copying errors can occur in the form of mutations or total loss of the gene. Dollo's law assumes all genes are lost or mutated in evolution, but recent research has shown that some, though by no means all, genes are retained and unmutated in evolutionary changes regarding them.

Those few genes that are retained have simply been randomly switched off rather than lost or changed gradually. Normally, of course, this would result in the death of the offspring, but occasionally the effect is neutral or beneficial and the gene remains switched off, inactive but still present, in the species.

"Silent genes" as they are called, are still subject to mutations and such like, so are estimated to last for just 6-10 million years in a state reasonable for safe reactivation. Other examples such as the dolphin therefore, are expected to be having been evolved from scratch.

Another explanation for their survival lies in the womb. Almost all vertebrates share a gene which is silent after birth but shows itself in the womb in the form of a notochord, the cartilaginous predescessor to the spine and acts a template for the bone. Other silent genes such as those which cause humans to possess tail buds in the womb have no apparent beneficial effect but are kept purely because they have no negative effect and most mutations of is are bad.

But ancient genes which have not been switched off have invariably been completly lost or mutated as to be unrecognisable. We do have what is known as "junk DNA" and this constitutes up to 98% of human DNA. This, known as non-coding DNA because it is not used to encode RNA in proteins, was until recently thought to be literally junk, mere remnants from our past. Now however, although it is still a very unexplored science, most of it is thought to have a function, because its removal from rats caused them to die almost immediately. The remainder are the silent genes.

So the answer to your question is yes, genes can be lost.

Answer 2

It is way too soon to tell exactly what happens with genes.. The mapping of the human genome just got into full swing at the beginning of the 2000's. By Using the shotgun technique they were able to break down and decipher The meaning and placements of genes. Like take for instance IGF2R is the genome specifically targeted for intelligence. People with this gene usually are about 10% smarter than people without it. But having all this information does not tell us what was going on a million years ago.. but as time unfolds and more data is accumulated your questions will be answered.

I do know about the human tail bone though. Yes some people are born with a extra link in their tailbone and are suseptable to injuring it. sometimes it shows on the exteirior of the skin but usually it is hidden. Just another little tidbit. some humans are born with an extra set of ribs also.

Answer 3

No. Genes can be lost.

When DNA is copied, many things can go wrong. At the small scale, there might be a mis-incorporation of a nucleotide [something like a typo] up to whole genome duplication events where everything is copied but not separated [printing press error]. Likewise, there are cases where big chunks of DNA are lost during replication [missing pages] or when one or more typos is enough to break a gene in effect.

There are organisms that have lost so many genes that they are barely considered alive. Mycoplasma are a group of bacteria that have tiny genomes, some as small as 600 Kb. They are related to other bacteria with much larger genomes so they have shed most of their genes.

Answer 4

About 80-90% of the human genome includes "junk" DNA, which is the DNA that doesn't code for any specific protein. These are most likely genes from ancestors that have become non-functional. The genes aren't really our ancestors, since they aren't functional anymore, but are what's left after multiple multiple mutations.

Yes, humans have a post-anal tail during development. All vertebrates do.

Although I don't believe that there are any current whales that have legs, they still have their hip bones, as they are used for sexual reproduction.

Answer 5

Our DNA contains a lot of inactive or fossil genes. These genes are left over from ancestors but are no longer active.

New genetic studies can use this information to verify other evidence of evolution.

Answer 6

Early embryos also have gill slits.

"Nearly 100% of all the living plant and animal species--from complex mammals to the simplest bacteria--use the exact same genetic code (the exact same set of chemical instructions) to direct the assembly of the many different kinds of protein molecules that living bodies need in order to function. The fact that this genetic code--the chemical "rule book" for making proteins--is exactly the same in essentially all organisms (with only a few very minor exceptions) is itself very strong evidence that all living species are related to each other and evolved out of a long series of common (shared) ancestors."
http://www.mukto-mona.com/science/skybreak/scienceofevolution.pdf
page 203

Answer 7

yes , its true , genes get suppressed but don't disappear totally. only a small portion of the genome is functional at a time , in an organism . reactivation of earlier dormant parts of genome , and getting abnormal characters thus ( as u have sighted examples above ) is called altruism.

Answer 8

hi,
Many researchers are inserting foreign genes into crop plants to make them grow bigger and better. Others are developing methods for destroying foreign genes that have done their job, to ensure that they don't spread to wild plants.

One new way of performing this deletion trick involves putting segments of DNA, called flip recombinase targets (FRTs), on either side of the foreign gene, explains Thomas K. Hodges of Purdue University in West Lafayette, Ind. The plant also gets a flp gene, which controls an enzyme that attaches to FRTs and excises the gene between them.

In the ...