9

Retroviruses depend on being able to convert their RNA genome into a DNA copy, and have a reverse transcriptase enzyme to do that. This unique activity is not found in human cells, allowing for potential antiviral therapy if a drug can be used to inhibit the reverse transcriptase while not affecting the human enzymes. AZT is one such drug, by mimicking the ...


9

Cancer cells and normal cells differ on the genetic basis but they share the same genetic background, so they have not different DNA in the sense of two different people. They have to be different, since cancer cells have to accumulate mutations on a number of genes to become a cancer cell, which can survive and will not be directed into apoptosis. These are ...


8

A few components to my answer. Red blood cells do not contain a nucleus, therefore, they do not harbour DNA. The major determinant of blood compatibility is the blood antigen. There are only 4 types: O, A, B, AB. This is genetically encoded, and is expressed as a set of sugar coats on the blood cell membrane. However, the enzymes that encode for A or B ...


6

Second law of thermodynamic and ageing The second law of thermodynamic applies to closed system. Organisms are not closed system. The second law of thermodynamic is a fundamental principle of our universe and any biological processes do follow the principles of physics. However, stating that biological ageing is (partially) caused by the second law of ...


6

This is a very interesting question and I had not thought about it before. I am reiterating the background of your question. Background Cas9 cuts the both the strands of the target DNA at the same location thereby making a blunt end cut. Usually sticky ends and microhomologous ends lead to indels because of exonucleolytic clipping and addition of extra ...


6

Non-homologous end joining indeed induces errors in the affected sequence. But you have to keep in mind, that NHEJ is an emergency repair mechanism which involves a "repair or die" chance. If the chromosomal break is not repaired it is not unlikely that the cell will get into apoptosis, or, even worse, develops into a cancer cell. Introducing small errors is ...


6

DNA mismatches and indels can be repaired after replication through an aptly named mechanism called DNA mismatch repair. I'll briefly describe the mechanism in Escherichia coli, but it's similar in other organisms. A protein called MutS scans DNA for lesions caused by mismatched nucleotides incorporated during replication that escaped DNA polymerase ...


5

Have you read the DNA repair article on Wikipedia? The DNA damage and mutation section answers exactly what you're asking: DNA damages and mutation are fundamentally different. Damages are physical abnormalities in the DNA... [and] can be recognized by enzymes, and, thus, they can be correctly repaired if redundant information, such as the undamaged ...


5

In germ cells telomerase enzyme is active and elongates telomeres, so youngsters are not born older than their parents due to telomeres. Still, they do receive mutations, accumulated by their parents' germ-line cells, i.e. eggs and sperm. Most of the mutations occur upon division of the cell. Egg cells don't undergo many divisions - they are created in the ...


5

In eukaryotic cells there is no difference between a mother and a daughter cell - the later is an exact copy of the mother cell. This is true for yeasts as well for example for human cells. The only thing that happens over time is that the telomeres at the end of the chromosomes get shorter (unless the cell has an active telomerase which most cells doesn't) ...


5

To record the current methylation state of your DNA, you can use bisulfite sequencing. Basically, you take half of your DNA sample and treat with bisulfite, which deaminates cytosines (C->U) , so they read as T instead of C. Methylated cytosines are protected, so they still read as C. You run two sequencing reactions, one with bisulfite-treated and the other ...


5

Is there a point in our life when ALL the atoms from our childhood's body gets replaced? No. There is no point where ALL atoms have been replaced. This has been shown by tracing distinct carbon isotopes in DNA [which reflect upon atmospheric 14C at the year of their generation (which reflect the extent of human atom bomb testing)]; Bergmann et al. 2009, ...


4

Does this mean that if one (or both) parents have something major missing (like a limb), the kid will come out without a limb? Unless there is a genetic basis to the missing limb, no. Even for people born with missing limbs, this is usually not caused by genetics, but by a problem during limb formation in the womb (for example, through medication taken by ...


4

No, similarity is not measured in base pairs. They are talking of regions of cross-over being marked by at least 200bp of highly similar sequence between the two strands involved in exchange.


4

Cancer is commonly defined as uninhibited cellular replication caused by mutations to the genome. Genes where cancer-causing mutations have been identified are known as oncogenes; the COSMIC (Catalogue Of Somatic Mutations In Cancer) database lists all of the known oncogenes (547 to date - 23rd Jan 2015 - 1% of all human genes!) [1]. The effect of a ...


4

Background to the different theories of ageing. This video, from a senior lecturer at the University of Liverpool who specialises in ageing, discusses the theories of ageing. He touches on the DNA damage theory. DNA damage theory of ageing. Note that when talking about DNA damage theory, we are specifically talking about damage to the process of cell ...


4

Okay, you have a lot of questions there. I'll try to give some answers, but if you want more details or background knowledge I'd recommend you to read /study more about immunology (none of your questions are actually about molecular biology or cell biology). 2) Foreign cells are generally recognised by the immune system, based on the HLA molecules on the ...


3

NHEJ is indeed error prone. It is called "non-homologous" because it does not use a "homologous" template from another sequence-matching piece of DNA to guide the repair. Homologous repairs avoid causing mutations because the similar string of DNA acts as a template so that the cell knows what letters to put into the gap. When there's no template, there's ...


3

Because one's DNA doesn't have to exactly match another person at all 3 billion locations for the transfusion to be successful. As it turns out, there are only a few proteins that determine whether a person's blood is a match to someone else's. And as it turns out, in the vast majority of the human population, there are only three alleles of the ABO gene, ...


3

The Stanford article that you read is correct, in the sense that telomeres do not need to be completely removed by cell division before deleterious effects occur and cells start undergoing senescence. This Nature article describes an experiment in which the minimum length of telomeres (beyond which chromosomal fusion occurs) was determined: The critical ...


3

Not only pure DNA, UV radiations are one of the main causes of skin cancer because they damage cellular DNA in skin cells. Talking about frequency range, two different types of UV radiations damage DNA in two different ways: UV-A radiation damages DNA in indirect ways. UV-A radiation easily generates free radicals, such as hydroxyl and oxygen radicals, ...


3

It seems very feasible to synthesize human DNA (please inform my ignorance, if I'm wrong. lol.) and it looks very promising after reading this: https://www.wired.com/story/live-forever-synthetic-human-genome/. It is certainly possible to synthesize human DNA, but it's another thing to create a functional chromosome. In fact, in the article you link to,...


3

While your DNA gets damaged, not every single cell will have the same damage. Your consensus DNA sequence will not change.


2

It is critical for you to realize that one's DNA is not the determining factor when it comes to a blood transfusion. Rather, what you have to look at is the proteins being expressed by the DNA coding for blood-associated proteins, as it is these proteins that are the determinant of blood acception or rejection.In other words, the key question is whether or ...


2

It is not unlikely that nicking is causing trouble. The question is if repeated freezing and thawing is causing the problem, there is an article which has been published in B.R.L. Focus in 1983 which disputes this effect. You can find the PDF with the article here, the article itself starts on page 10 in the PDF. On the other hand there is this paper ("...


2

Mutation of DNA can be caused by an exogenous or endogenous source. Many external factors like irradiation or chemicals induce mutations. Some endogenous mutations arise from oxidative stress, insufficient DNA repair or spontaneous mutations on the molecular level. There are many mechanisms for DNA repair like base excision repair, nucleotide excision ...


2

The EMF/RF doesn’t directly damage the cell. It just deranges cellular metabolism. The free radicals that are produced by this change in metabolism are what causes the damage. OXIDATIVE STRESS AND DAMAGED DNA In contrast with Xrays and gamma rays, Microwave radiation does not have sufficient power to directly break covalent bonds in DNA molecules. But ...


2

The thing about DNA is that it's very durable, compared to the rest of the cell. It's not too difficult to extract DNA from cooked and processed food, even though the definition of "cooked" is "denatured and broken many of the proteins in the cell". The long DNA strands may be broken into long pieces, but overall the DNA holds up very well to heat. There's ...


2

It is widely accepted that birds are in fact dinosaurs. Cladistically speaking, no DNA technology is required to create a living dinosaur, as they already exist. Assuming you want to do the same to a non-avian dinosaur (a paraphyletic group), however, a better idea would be to ask on World Building SE, as there have been little to no scientific research on ...


2

Excellent question! You would definitely be able to find quite a few sequences of DNA that are undamaged (in fact most of them would be undamaged), but it is very unlikely that any cells in his/her body would have a perfect copy of the entire original genome. I'm sure that cells closer to the skin (exposed to more radiation) would have more mutations, but ...


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