Recent comments in /f/askscience

sommerniks t1_j99imxo wrote

Reply to Can doctors tell when cancer is caused by something specific, such as smoking or chemicals? by [deleted]

Sometimes. If you have an HPV related cervical cancer and claim you're a virgin they're not really going to believe it.

Also, about the smoking: lying about it won't always work because they have noses and you're going to be wanting to take cigarette breaks during your hospital stay. If you quit smoking a while ago you're likely to mention it because quitting is a positive thing.

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shaokim t1_j99heib wrote

Reply to comment by 0oSlytho0 in Can doctors tell when cancer is caused by something specific, such as smoking or chemicals? by [deleted]

To add to this: we can't determine the exact reason why cancers were caused in the great majority of cases. However, there are cases and certain types of cancer where we can determine with great confidence that a certain cause was at its origin.

For example, in cervical cancer, usually caused by a virus called Human Papilloma Virus, that same virus leaves a kind of hallmark when viewed under the microscope called a koilocyte. AFAIK, detecting cancer of squamous cells in the cervix together with koilocytes OR the actual isolation of the virus is pathognomonic for HPV-caused cervical cancer.

For people with familial cancer syndromes, like Familial Adenomatous Polyposis (FAP), if a person comes in at an early age ie. 25 years old, and we see on colonoscopy a colon that is littered with growths, and after biopsy one of those growths comes back as malignant, we can tell with a high degree of certainty that the familial cancer syndrome (the heritable gene defect) was at the cause of the cancer.

Another type is a mucosa associated lymphoid lymophoma of the stomach. If we find a bacterium called Helicobacter pylori in the stomach, together with a tumor we determine to be a MALT lymphoma, and especially if that tumour regresses in antibiotic therapy, we can determine with high certainty that H. pylori caused that exact tumour, IIRC.

Actinic keratosis is a skin condition that's caused by chronic excess UV-exposure (usually the Sun). It can lead to the development of skin cancer. If skin cancer arises from actinic keratosis, we can say with a high degree of certainty that UV light caused it.

There are many more examples: liver cancer in a patient with an alcoholic cirrhotic liver; esophageal cancer on the part closest to the esophagus in know stomach acid reflux, etc etc…

these may not be ‘caused by this definite exact cause’ but ‘caused by this to a high degree of certainty’.

There's bound to be more examples in genetic cancer syndromes (such as Li-Fraumeni, Multiple Endocrine Neoplasia) and infectious cancer syndromes.

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SystemFantastic1090 t1_j99fzu1 wrote

Reply to Why is Turner's syndrome a problem if only one X chromosome is active? by NimishApte

It’s a myth that every single gene on the X chromosome is silenced during X-linked inactivation. In reality, many escape inactivation and are still expressed. It’s the lack of these that cause many (if not all) of the problems in Turner’s syndrome.

If you want to read up more on which escape X-inactivation, search “four core genotype” model and go from there

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Cheetahs_never_win t1_j99frb4 wrote

Reply to When something is bent (a metal ruler for example) and returns to its original shape, what is happening on the molecular level? Where is the information of the original shape stored and what forces do the unbending? by JewNugget2525

There are a lot of different things that can happen, based on material and lattice structures temperature, etc.

If it's elastically deformed and released, the stored energy snaps it back into place.

If you deform and hold it, the stored energy can cause the lattice structure to shift over time in a process called ratcheting in order to permanently deform. Increased temperature speeds up the process.

If you go past elasticity, then you can think of the material acting like ice flows moving around past one another, though on a macro scale, it tends to act like a really stiff taffy, depending on the ductile nature.

It can even change the lattice structure from one kind to another, giving it properties of the same material in those alternative lattice structures.

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tzl-owl t1_j99dhx8 wrote

Reply to comment by Stats_Think in Just with a sample of someone's DNA, can a lab tell the approximate age of a person? by Blakut

In terms of feasibility today, telomeres YES, but mutations NO. I work in that area and will say that current technology isn’t accurate enough to spot mutations in single cells which is what you’d need (it works in cancer which have clonal expansions of mutated cells and gives you better variant call confidence). Right now sequencing error rates are too high still.

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