Recent comments in /f/askscience

a_common_spring t1_j4g6bxs wrote

Reply to How accurately can medicine pinpoint causes of cancer? by GuptRX

Cancer is when cells overgrow due to mutations in genes that affect the cell cycle, so cells start to reproduce and replicate without the controls. Control mechanisms within the cell cycle usually detect and repair bad DNA, and they make sure the cell doesn't reproduce at too high a rate, and they make sure that cells die at the right time.

Sometimes people are born with an inherited mutation that may contribute to cancer, but about 90% of cancers are caused by mutations that arise in the individual during their life. There's nothing from looking at a mutation to say what caused it, unless they look at your family members and decide that it was an inherited mutation.

The way they decide some chemicals are carcinogenic is that exposure to them correlates with higher rates of some kind of cancer. But they can't look at the mutation itself and say what caused it.

If you get a type of cancer that they have already noticed is highly correlated with exposure to a chemical you work with, then they might be able to say that your mutation was probably caused by that chemical.

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imeuru t1_j4g3jvs wrote

Reply to Is there an upper limit on the size of a ship? by LilyFish-

They already make ships that are as big as cities, have you ever stood next to a large cruise ship? They're way bigger than you think, larger than freight ships and air craft carriers, and they can house thousands of people.

The largest cruise ship in the world is a cruise ship called Wonder of the Seas, it's *1,187.8 feet long (that's almost 1/4 mile) and can carry up to 6,988 passengers.

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fleur_essence t1_j4g2v4w wrote

Reply to comment by DifferentCard2752 in Is there physical differences between blood types? by terrip_t1

Kidd antigens: A red cell has a ton of molecules on the cell surface that helps it do what a cell gotta do. One such molecule is an ion transporter (helps urea travel from one side of the cell membrane to the other. Almost all people have this protein, but at some point there was a mutation, so about 50% of people have “version a” while about 50% of people have “version b” and another 25% have both “Jka” and “Jkb”. These are the main Kidd antigens (Jka and Jkb are abbreviations). So, really there’s nothing special about having a Kidd antigen on your red cell. The problem happens if you’re missing one (ie type Jkb only) and get exposed to some blood from a Jka person. There’s a chance your immune system notices the difference and forms anti-Jka antibodies. Once the hospital knows you have formed this antibody, they’ll do their best to give you Jka-negative blood to prevent the transfusion from being destroyed by your immune system.

Just as an aside, there are tons of different blood group system (types of molecules on the red blood cell surface that can vary between one person and another). It’s impractical to “match” a blood unit up front to each persons molecules except for the ABO and Rh+/- everyone’s talked about. So we only special-select blood if there’s a known antibody, with the exception of sickle cell patients.

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