DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and Radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day.[1] Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell’s ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell’s genome, which affect the survival of its daughter cells after it undergoes mitosis. Consequently, the DNA repair process is constantly active as it responds to damage in the DNA structure.
DNA damage, as distinct from mutation, is a primary cause of aging. Contrary to popular belief, experimental evidence has failed to show that mutation cause aging.
What is the difference between DNA damage and DNA mutation?
Damage is a physical abnormality in DNA. It can be detected by enzymes and repaired. Most commonly, one side of the double helix DNA strand is damaged (see illustration, right), but double strand breaks also happen and can be repaired.
Ad DNA mutation is a change in the base sequence of the DNA. In other words, both sides of the DNA strand changes. A mutation cannot be recognized by enzymes once the base change is present in both DNA strands. Mutations cannot be repaired.
At the cellular level, mutations can cause alterations in protein function and regulation. Mutations are replicated when the cell replicates. In a population of cells, mutant cells will increase or decrease in frequency according to the effects of the mutation on the ability of the cell to survive and reproduce. Although distinctly different from each other, DNA damages and mutations are related because DNA damages often cause errors of DNA synthesis during replication or repair and these errors are a major source of mutation. – wiki
The rate of normal DNA repair in your healthy cells is amazing.
In humans, DNA damages occur frequently and enzyme mediated DNA repair processes have evolved to cope with them. On average, about 800 DNA damages occur per hour in each cell, or about 19,200 per cell per day (Vilenchik & Knudson 2000). – wiki
The rate of DNA repair is dependent on many factors, including the cell type, the age of the cell, and the extracellular environment. A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred to its DNA, can enter one of three possible states:
an irreversible state of dormancy, known as senescence
unregulated cell division, which can lead to the formation of a tumor that is cancerous
The DNA repair ability of a cell is vital to the integrity of its genome and thus to its normal functioning and that of the organism. Many genes that were initially shown to influence lifespan have turned out to be involved in DNA damage repair and protection.[2] Failure to correct molecular lesions in cells that form gametes can introduce mutations into the genomes of the offspring and thus influence the rate of evolution. …
Can our thoughts influence the rate of DNA repair? I don’t know about that, but our thoughts can influence our actions, and our actions can cause us to eat right, exercise, get enough sleep, to seek clean fresh air and water and to find comfort in our relationships.
If a Human-Chimp hybrid was created, would more people believe we share a common ancestor? I think a few more would. The DNA evidence is already clear enough regarding our evolution, but a humanzee would make the point viscerally. Some are worried it will happen soon.
The humanzee (also known as the Chuman, or Manpanzee) is a hypothetical chimpanzee/humanhybrid. Chimpanzees and humans are very closely related (95% of their DNA sequence, and 99% of coding DNA sequences are in common[1]), leading to contested speculation that a hybrid is possible, though no specimen has ever been confirmed.
I previously thought this was impossible because we have different numbers of chromosomes, but it turns out chromosomal polymorphism is possible.
It has also been studied in alfalfa,[2]shrews,[3] Brazilian rodents,[4] and an enormous variety of other animals and plants.[5] … All forms of chromosomal polymorphism can be viewed as a step towards speciation. Polymorphisms will generally result in a level of reduced fertility, because some gametes from one parent cannot successfully combine with all gametes of the other parent. However, when both parents contain matching chromosomal patterns, this obstacle does not occur. – wiki
Interestingly, one of our chromosomes is two of the smaller ape chromosomes that fused together in our ancestral past.
Humans have one chromosome fewer than other apes, since the ape chromosomes 2p and 2q have fused into a large chromosome (which contains remnants of the centromere and telomeres of the ancestral 2p and 2q) in humans.[2] Having different numbers of chromosomes is not an absolute barrier to hybridization. Similar mismatches are relatively common in existing species, a phenomenon known as chromosomal polymorphism.
The genetic structure of all the great apes is similar. Chromosomes 6, 13, 19, 21, 22, and X are structurally the same in all great apes. 3, 11, 14, 15, 18, and 20 match between gorillas, chimpanzees, and humans. Chimps and humans match on 1, 2p, 2q, 5, 7 – 10, 12, 16, and Y as well. Some older references will include Y as a match between gorillas, chimps, and humans, but chimpanzees (including bonobos) and humans have recently been found to share a large transposition from chromosome 1 to Y that is not found in other apes.[3]
Are we genetically similar enough to have a living hybrid?
“Chimpanzees (Pan troglodytes) and human beings (Homo sapiens) are placed taxonomically in different genera, Pan and Homo, respectively. These species are much alike in anatomical and physiological features as well as in DNA and protein composition. Comparisons of chromosomes show basic similarities with a few superimposed structural rearrangements. The overall number of chromosomes is comparable (46 for Homo, 48 for Pan). Homologous pairs can be identified, and general chromosome structure can be matched band for band between the pairs. … (Gardner, 1991, p506). – asa3
Even after our species split from early apes, our ancestors interbreed again over a million years later.
Looking back millions of years into early human history, current research into human evolution tends to confirm that in some cases, interspecies sexual activity may have been a key part of human evolution. Analysis of the species’ genes in 2006 provides evidence that after humans had started to diverge from chimps, interspecies mating between “proto-human” and “proto-chimps” nonetheless occurred regularly enough to change certain genes in the new gene pool:
“A new comparison of the human and chimpgenomes suggests that after the two lineages separated, they may have begun interbreeding… A principal finding is that the X chromosomes of humans and chimps appear to have diverged about 1.2 million years more recently than the other chromosomes.”
The research suggests that:
“There were in fact two splits between the human and chimp lineages, with the first being followed by interbreeding between the two populations and then a second split. The suggestion of a hybridization has startled paleoanthropologists, who nonetheless are ‘treating the new genetic data seriously.’[1]
At this point we are about 6 million years different from apes, and I don’t know anyone who finds apes attractive so I highly doubt there will ever be a natural hybrid.
Would it work in theory? Dr. MacKellar things so.
In an interview with The Scotsman, Dr Calum MacKellar, director of research at the Scottish Council on Human Bioethics, warned the controversial draft Human Fertilisation and Embryology Bill did not prevent human sperm being inseminated into animals. He said if a female chimpanzee was inseminated with human sperm the two species would be closely enough related that a hybrid could be born. He said scientists could possibly try to develop the new species to fill the demand for organ donors. Leading scientists say there is no reason why the two species could not breed, although they question why anyone would want to try such a technique. – scotsman
Has it ever been attempted in a laboratory setting?
Yes. Soviet Professor Ilya Ivanov attempted to create a human-ape hybrid, but there is no evidence of any success.
[Stalin's] weirdest move was to pony up $300,000 and order
artificial insemination pioneer Ilya Ivanov to produce a human/chimpanzee hybrid: “I want a new invincible human being, insensitive to pain, resistant and indifferent about the quality of food he eats.” Ivanov had previously studied a zeedonk (zebra plus donkey), a zubron (European bison plus domestic cow), an antelope/cow, a mouse/guinea pig, and
other novel blendings. Between 1926 and 1930 he made several attempts to conceive a humanzee which all failed, though it should be noted that many of his setbacks were circumstantial and sociopolitical (I’ll say) rather than biological.
Rumors of Humanzees
There are various rumors of humanzees in the past, but none have been proven to be true.
Stories of such paradigm-jarring creatures have circulated since at least as far back as Pope Alexander II in the eleventh century, but so far proof is elusive. Belgian cryptozoölogist Bernard Heuvelmans co-authored a book in 1974 that contained an account from a Russian Gulag escapee, a doctor, claiming a slave race of human/gorilla hybrids had been produced. They were supposedly furry and strong but sterile and made indefatigable salt miners. And in 1987 Florence University dean of anthropology Brunetto Chiarelli said that a secret experiment did conceive a viable humanzee zygote (in vitro, one hopes) but, for ethical reasons, after a number of routine cell divisions the mass was destroyed.
I once nosed around the small town of Dulce, New Mexico with a reporter from the Sacramento News and Review many years ago. In Dulce, it is rumored that a secret underground lab with many levels houses many different kinds of human-hybrids.
I didn’t find a thing, but we were a bit freaked out to be stopped by a group of heavily armed men at a night time roadblock on the way out of town. I’ll save that story for another time.
Finally, some evidence:
Some related questions, notes:
__________________________
What other hybrids have happened?
in April 2006 a hunter in Canada’s North-west Territories shot a polar bear whose fur had an orange tint. Research showed that it had a grizzly bear father, and it became known as a pizzly. … Lions and tigers have been bred to create ligers, the world’s largest cats. And there are also zorses (zebra and horse), wholphins (whale and dolphin), tigons (tiger and lion), lepjags (leopard and jaguar) and zonkeys (zebra and donkey). As well as these hybrid mammals, there are also hybrid birds, fish, insects and plants.
Are all hybrids sterile?
Many hybrids, such as mules, are sterile, which prevents the movement of genes from one species to another, keeping both species distinct. However, some can reproduce and there are scientists who believe that grey wolves and coyotes mated thousands of years ago to create a new species, the red wolf.
Here Richard Dawkins, who is banned in Turkey according to his web site, makes the point that atheists are rarely terrorists.
The next two videos are a bit to quiet, but this is the first time I’ve heard of Dawkins, so I was curious to hear what he had to say on the topic of God and Aliens:
Richard Dawkins at the Edinburgh International Book Festival on Monday, August 11, 2008. The interview was conducted by Paula Kirby.
United States Senator John McCain has said there is enough evidence of the involvement of former Inter-Services Intelligence officers in the planning and execution of the Mumbai attacks.
If Pakistan did not act swiftly to arrest the people involved, the Senator said, India would be left with no option but to conduct aerial operations against select targets in Pakistan.
Senator McCain, the Republican presidential candidate who lost to Barack Obama, told a select group of Pakistanis at an informal lunch in Lahore on Saturday that this was conveyed to him by Prime Minister Manmohan Singh in New Delhi.
Ejaz Haider, a senior editor at the Daily Times, who was at the lunch said Mr. McCain told the group that Washington would not be able to do much to stop India, as the Mumbai attacks were its “9/11.”
“The democratic government of India is under pressure and it will be a matter of days after they have given the evidence to Pakistan [that they decide] to use the option of force if Islamabad fails to act against the terrorists,” Mr. Haider quoted the Senator as saying.
Mr. McCain, who arrived in Pakistan from New Delhi on Friday and met Prime Minister Yousuf Raza Gilani in Islamabad in the evening, told the group that Dr. Singh was “visibly angry and reeling from the shock of the attacks.”
He said if Pakistan did not act to get the “bad guys,” India would have no option but to use force.
“We were angry after 9/11. This is India’s 9/11. We cannot tell India not to act when that is what we did, asking the Taliban to hand over Osama Bin Laden to avoid a war and waging one when they refused to do so,” Mr. McCain said.
President-elect Barack Obama promised Saturday to create the largest public works construction program since the inception of the interstate highway system a half century ago as he seeks to put together a plan to resuscitate the reeling economy.
Not a bad start, but we can’t keep building bigger credit bubbles on top of the one that just burst.
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DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and Radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day.[1] Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell’s ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell’s genome, which affect the survival of its daughter cells after it undergoes mitosis. Consequently, the DNA repair process is constantly active as it responds to damage in the DNA structure.
DNA damage, as distinct from mutation, is a primary cause of aging. Contrary to popular belief, experimental evidence has failed to show that mutation cause aging.
United States Senator John McCain has said there is enough evidence of the involvement of former Inter-Services Intelligence officers in the planning and execution of the Mumbai attacks.
