Wikipedia:Reference desk/Archives/Science/2013 August 31

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

August 31

DNA and heredity

Hello. Perhaps this is a simple question and I'm just not seeing an answer anywhere, but I'm trying to understand if (for example) I, as a male, could have inherited any traits from my paternal grandmother. In this scenario, my father would have inherited a Y chromosome from his dad and an X chromosome from his mom. He would have passed the Y chromosome (i.e. only his father's genetic material, not his mother's) on to me and my X chromosome would come from my mother. Is this right? Or is there some other process whereby I would have inherited genetic material from my father's mother?--William Thweatt ^TalkContribs 01:04, 31 August 2013 (UTC)

You have another 22 chromosome pairs besides X and Y, which come from both of your parents, and are constructed from DNA passed on by all four of your grandparents. See the introduction of Human genome. Someguy1221 (talk) 01:23, 31 August 2013 (UTC)

More specifically, you've inherited 25% of your genetics from your paternal grandmother. As you have from your other three genetic grandparents. --Jayron32 01:29, 31 August 2013 (UTC)

Ah, yes. It's all coming back to me now. Thanks all. It's been a long time since Biology 101 for me. :) --William Thweatt ^TalkContribs 01:42, 31 August 2013 (UTC)

The 25% is a good approximation, but you might actually inherit slightly more from your paternal grandfather than your paternal grandmother, since you definitely have his Y and have only a 50% chance of having that grandmother's X. Also, sometimes genes can jump from one chromosome to another. StuRat (talk) 02:43, 31 August 2013 (UTC)

Presuming that William is male, he has zero chance of having that grandmother's X. A man's X always comes from his mother. (A woman gets one from her mother and one from her father.) Looie496 (talk) 02:58, 31 August 2013 (UTC)

Good point. Correcting for that, with 46 chromosomes, a male should, on average get 1 (Y) + 44/4 chromosomes from his paternal grandfather, 44/4 chromosomes from his paternal grandmother (no sex chromosome), and 1/2 + 44/4 chromosomes from the additional two maternal grandparents, as either might contribute the X. So, that's 12 + 11 + 11.5 + 11.5 = 46. As a percentage, that works out to be 26%, 24%, 25%, and 25%. StuRat (talk) 10:10, 31 August 2013 (UTC)

There's no either, just as with autosomes both maternal grandparent will contribute to the X chromosome a male inherits as recombination will almost definitely occur (if it does not, this generally means major problems so the whole calculation may be out of wack). In case this is still confusing, this means the X chromosome the male inherits from his mother is not her father's X chromosome nor her mother's X chromosome but a chromosome combining their two (maternal grandparents) chromosomes in some way. (The X chromosome the maternal grandmother contributes is likewise a combination of the two X chromosomes she has. In fact even the X chromosome from the father is not simply the X chromosome he inherits from his mother but a combination of his X and Y chromosomes although the Pseudoautosomal regions are small enough that it doesn't really screw up your statistics to assume it is.) Also I question the usefulness of counting percentages in terms of number of chromosomes, it makes much more sense to either use base pairs or perhaps genes (the former is of course far simpler than the later), and the differing size of the chromosomes means the values you will get will be sufficiently different. Nil Einne (talk) 16:05, 31 August 2013 (UTC)

Erm, StuRat, you're confusing people. Barring aneuploidy of some sort, no matter what the pedigree, you get one of each pair of chromosomes from each parent. If you look at the person you can figure out which sex chromosome he got from his father, and thus from successive ancestors, but he or she always traces one or another of them back that far! Though you might say the X chromosome is bigger and better, so inheriting a Y doesn't count for as much. But you can't really quantify that absolutely in a particularly meaningful way. (you could count basepairs, but does the "junkiness" of a Y make it count for even less?) Wnt (talk) 22:46, 3 September 2013 (UTC)

If we're just talking about autosomal DNA here, the 25% has to be understood as a statistical average. When germ cells (sperm and eggs) are made, genetic recombination causes the paternal and maternal copies of each pair of chromosomes to exchange some DNA. This means that while you carry 22 autosomes that are entirely paternal and 22 that are entirely maternal, your germ cells carry autosomes that each contain a mix of paternal and maternal DNA. So your children do not carry the exact same chromosomes as you. Since this process is totally random, you may inherit more or less than 25% from each particular grandparent, but the average will be 25%. Someguy1221 (talk) 03:56, 31 August 2013 (UTC)

weathern pattern significance

Back in the early-to-mid 1980s, when I was a kid, I heard a foghorn sounding off at night during a rainstorm in San Francisco. Why would an authority need to turn on the foghorn during rainy weather at night?142.255.103.121 (talk) 04:09, 31 August 2013 (UTC)

Two reasons: (1) On a rainy night, it IS harder to see than on a clear day (anyone who's ever flown a small plane on a rainy night can appreciate just how much); and (2) even more importantly, along seashores (especially in the area around Frisco), such weather can often cause the cloud base to sink and ground fog to form -- hence the need for the foghorn. 24.23.196.85 (talk) 04:51, 31 August 2013 (UTC)

Same thing for a rainstorm during the day, right?142.255.103.121 (talk) 19:17, 31 August 2013 (UTC)

Calling it a "fog" horn is a bit of a misnomer - it's really a "poor visibility" horn. Hence it's gotta be sounded in heavy rain or snow as well as in fog. Also in an era before weather satellites and weather radar - nobody knew what the visibility would be like further from shore - so you'd definitely want to err on the side of caution. SteveBaker (talk) 21:56, 31 August 2013 (UTC)

Are dogs born in winter less smelly than dogs born in summer?

Just heard one of my friends say so--朝鲜的轮子 (talk) 04:57, 31 August 2013 (UTC)

I wouldn't think so, although an outdoor poo will smell less in winter, as it will rapidly cool and freeze. Of course, if you don't pick them up, you're in for a rude surprise in spring. :-) StuRat (talk) 09:59, 31 August 2013 (UTC)

If you live in a hot, dry climate the quick drying of the deposits makes them less offensive and problematic than being somewhere where they stay damp and squishable. But all if this has nothing to do with when the dog was born. Had dogs all my life, Never heard of that, and can't think of any reason why that would make a difference. HiLo48 (talk) 22:26, 31 August 2013 (UTC)

I think my friend mean a dog's skin odor. Looked up Dog odor, but found nothing about skin odor except "Dogs only produce sweat on areas not covered with fur, such as the nose and paw pads, unlike humans who sweat almost everywhere. However, they do have sweat glands, called apocrine glands, associated with every hair follicle on their body. The exact function of these glands is not known, but they may produce pheromones or chemical signals for communication with other dogs.".--朝鲜的轮子 (talk) 01:29, 1 September 2013 (UTC)

Polonium hydride

Is it PoH₂ or H₂Po? Double sharp (talk) 15:15, 31 August 2013 (UTC)

There is an article about it Polonium hydride Widneymanor (talk) 16:39, 31 August 2013 (UTC)

Which unfortunately wavers on the issue:( (I suspect Ds knows this, but for others...) The same formula written one way or the other suggests which atom is more cationic vs anionic. Naming it "[some-metal] hydride" (meaning Po is more metallic and has "hydride" anions) contradicts comments about it having chemical analogs to chalcogenides where the Po has anionic forms. So to respond to the question sort-of..."what's really the goal of your question? To understand the nature of the chemical, or to decide how to write it in some [as yet unstated] context?" DMacks (talk) 20:04, 31 August 2013 (UTC)

Yup, the sources I've seen tend to disagree on this! Bagnall calls it polonium hydride with PoH₂ (IIRC), while Thayer (a ref at element 117, talks about heavy main group elements) calls it H₂Po! Po has a slightly lower EN (2.0) than H (2.20); that would imply that Po is the cation, but is there something else at work here? (And should we list it in the Po compounds template under Po(II) or Po(−II)?) It's more of understanding the nature of the compound than writing it.

(Hydrogen astatide has a similar issue with HAt vs AtH...) Double sharp (talk) 03:25, 1 September 2013 (UTC)

...much as which we habitually write "H₂O" rather than "OH₂" or "HOH" or even "HHO". SteveBaker (talk) 21:24, 31 August 2013 (UTC)

For the molecular compound, it should always be written as H₂Po. IUPAC determines the order in empirical formulae to be row 7→ row 2; group 18 → group 1 → group 2 → Actinium → Lawrencium → Lanthanum → Lutetium → group 3 → group 15 → Hydrogen → group 16 → group 17. Plasmic Physics (talk) 21:37, 31 August 2013 (UTC)

But if it really is a hydride rather than a polonide, this would be misleading, which is why I asked the question, albeit not that clearly (I've tried to remedy that now!) Double sharp (talk) 03:27, 1 September 2013 (UTC)

It would not matter, compositional formulae are ignorant of bond-type. Plasmic Physics (talk) 08:40, 1 September 2013 (UTC)

...And in case you were, wondering, hydrogen poonide is a molecular compound. Plasmic Physics (talk) 00:25, 4 September 2013 (UTC)

I was too lazy to look up the electronegativity of polonium, but it turns out that that article has two nice little tables, both of which put it as a little less than hydrogen. Does that clinch it as PoH2? Wnt (talk) 22:51, 3 September 2013 (UTC)

According to who? This is a reference desk. Plasmic Physics (talk) 23:15, 3 September 2013 (UTC)

Need help with Calculating the slope of the best fit line from a data table?

Basically we had to calculate the circumference and the diameter of several round objects and convert that into a number closest to PI...

Now we are supposed to Calculate the slope with it but our teacher made no attempt to explain to us how to do it and our textbooks provide no easy to understand way to coincides with the assignment.

Diameter/Independent    Circumference/Dependent  Ratio C/D

     4.5 cm                  10   cm               2.22
     2   cm                   7   cm               3.5
     2.5 cm                   8   cm               3.2
     6.8 cm                  21.8 cm               3.205
     2.9 cm                   8.8 cm               3.034

He was supposed to post a video on Blackboard but he is so computer illiterate that it is sad. He never explains stuff and makes the assignment difficult but does not really teach us how to complete it. I have spent two days on youtube trying to understand this but i feel he pulled this whoel thing out of his @$$! Sorry! — Preceding unsigned comment added by Jheckman1986 (talk • contribs) 20:38, 31 August 2013 (UTC)

The slope of a Simple linear regression without an intercept term is ${\hat {\beta }}=({\overline {xy}})/({\overline {x^{2}}})$, where the overline indicates the mean, y in this case is circumference and x is diameter. However, just calculating the simpler ${\hat {\beta }}=({\overline {y/x}})$ would give you pretty much the same answer in this case. Red Act (talk) 21:20, 31 August 2013 (UTC)

I suspect that the intent here is that you plot a graph of diameter versus circumference. If diameter is the "independent" variable - then it should be plotted along the horizontal X axis and the circumference being "dependent" goes up the vertical Y axis.

Next, you can (hopefully) observe that those points lie close to a straight line...so you can calculate the slope of a best-fit straight line through those data points and thereby deduce the equation for the circumference of a circle, knowing it's diameter. This is a very valid and scientific way to deduce such a relationship. Mathematicians will of course cringe at this because they have ways to prove beyond doubt that that relationship is...but I'm guessing that this experiment is to help you to understand how scientific relationships are deduced from experimental data.

The way to calculate the slope of a straight line is described in our slope article (look at the first equation).

SteveBaker (talk) 21:22, 31 August 2013 (UTC)

(I fixed the OP's chart.) I think what Steve is saying is to just plot the points and draw in what looks like a good line, then measure it's slope off the graph. There are many mathematical ways you could calculate the best fit line, instead, but each will give a slightly different answer. So, if your teacher didn't specify what to do, I'd take the easy way out and just draw in a line by hand (using a ruler, of course). StuRat (talk) 10:30, 1 September 2013 (UTC)

Note that most decent scientific calculators will have a linear regression feature built in, which can provide the slope for a given set of data.--Srleffler (talk) 07:11, 2 September 2013 (UTC)

Throwing away contact lenses

Is there a reason that monthly contact lenses need to be disposed of after a month of use (other than to enable the manufacturer to sell more contact lenses)? — Preceding unsigned comment added by 89.241.229.123 (talk) 21:01, 31 August 2013 (UTC)

Contact_lens#Replacement_schedule says that "Lenses replaced frequently gather fewer deposits of allergens and germs". By allowing gasses and liquids to flow through the lens, it's also possible for germs and allergens to lodge deep inside them where cleaning fluids may not penetrate. The article does also mention that "Quarterly or annual lenses, which used to be very common, have been discontinued by manufacturers who argue they are less comfortable but also can make more profit by forcing consumers over to more frequent replacement schedules." - which kinda backs up your theory that it's to enable them to sell more lenses. HOWEVER: What that sentence neither says nor implies is that you could wear 4-week lenses for months. It's quite possible that 4 week lenses really are only good for 4 weeks - and they the manufacturers simply stopped making the kind that last longer...do not assume that it's safe to use a 4 week lens for many months on the basis of this information...that might be very dangerous. SteveBaker (talk) 21:13, 31 August 2013 (UTC)

Why not sterilize contact lenses using UV radiation or ionizing radiation? Count Iblis (talk) 23:17, 31 August 2013 (UTC)

UV will destroy the polymers in the lens in a matter of hours [1]. 68.0.135.117 (talk) 23:20, 31 August 2013 (UTC)

The protein deposits are what I find to be the worst problem. You can sterilize them with hydrogen peroxide, but the protein deposits don't come off. I tried using bleach on them, but that also damaged the lenses. The original hard contact lenses could probably be cleaned indefinitely, but those really were uncomfortable, and, in my opinion, dangerous (they can cut your eyes). StuRat (talk) 10:21, 1 September 2013 (UTC)

herbicide for vines?

vine on the tree near the azaleas

vine in azaleas

About 2 months ago, vines were taking over our azaleas so bad that I had someone cut them out. It was so bad that they had to cut back most of the azaleas. Now the vines are coming back. Is there a herbicide or something that will get rid of the vines but not hurt the azaleas? Bubba73 ^{You talkin' to me?} 23:46, 31 August 2013 (UTC)

No, not to my knowledge. We have Roundup-ready corn, but not Azaleas. You can also get herbicides that selectively target grasses, but that won't help here either. The best removal tactics may depend in part on what type of vine. Does it have a woody stem? Is it English ivy or virginia creeper or porcelain berry or kudzu (all common and invasiv across much of the USA)? Anyway, for most woody vines, you can paint a small amount of Roundup on the stumps, directly after you cut the vines back. The vines will most likely resprout, but you can repeat the process over the course of a season or two, and the plant will get weaker and weaker each time. There is also some risk to the Azaleas, but if you don't spill any and only directly apply glyphosate to unwanted stumps (ideally on a hot day), you should be ok. SemanticMantis (talk) 00:22, 1 September 2013 (UTC)

(There is something wrong with the sections right now.) Thanks - I don't know what kind of vine it is, but I think it looks like the porcelain berry. I'll try to get a photo tomorrow. Bubba73 ^{You talkin' to me?} 00:42, 1 September 2013 (UTC)

Whoever found they had to cut back your azaleas to get at the vines is grossly negligent. You simply cut the vine stem (species is irrelevant unless it's dodder) at soil level, allow it to die, and then remove it later. There's absolutely no need to harm the plant on which the vine is growing. μηδείς (talk) 03:24, 1 September 2013 (UTC)

You're right - we aren't using them again. My wife was furious. He cleaned out the vines but cost at least a couple of years of growth. My wife and I planted them ourselves a few years ago. The vines are threatening to take over again. Bubba73 ^{You talkin' to me?} 04:25, 1 September 2013 (UTC)

Exactly what is being referred to by "vines" here? In my part of the world the word vine immediately brings up images of grape vines. Those in this section are being described as if they are some sort of weed. Is that the case? HiLo48 (talk) 04:30, 1 September 2013 (UTC)

I was wondering that, too! Whatever the type of weed, applying an appropriate weedkiller with a paintbrush (as described by SemanticMantis above) instead of a spray should stop the regrowth (after cutting down), though this method will require some patience. Make sure that the weedkiller is one rendered harmless by soil so that it doesn't affect the azalea. I've got rid of ground elder amongst other low-growing plants by this method (even though some "experts" claim that this is impossible without digging out). For some woody weeds, a selective hormonal weedkiller such as "SBK" (formerly containing 2,4-Dichlorophenoxyacetic acid and 2,4,5-Trichlorophenoxyacetic acid in the UK) might be quicker, but availability might be restricted by law. I think this has been replaced by Triclopyr for domestic use. Be careful, though, because azaleas are shallow-rooting, so any soil contamination might affect them. The really environmentally friendly method is to regularly remove new growth by hand as it appears, but that's very time-consuming. Dbfirs 08:35, 1 September 2013 (UTC)

See liana. In AU, e.g. cat's claw creeper is considered a weed of national significance [2]. Due to their extensive root systems, and growth of rhizomes and stolons, vines can be very challenging to remove. If you've never had to deal with aggressive, undesirable vines, consider yourself lucky! SemanticMantis (talk) 13:22, 1 September 2013 (UTC)

I've added two photos. Bubba73 ^{You talkin' to me?} 14:38, 1 September 2013 (UTC)

Yeah, that's grape (see leaf here. Contrary to HiLo's response above, grape is very much a weed, at least where I live (SW Ontario). I never tried herbicide in my war against it, but pulling it physically was an unending task. Good luck. :) Matt Deres (talk) 14:56, 1 September 2013 (UTC)

It doesn't produce Grapes, at least it hasn't so far. (Maybe it takes many years to do that.) Bubba73 ^{You talkin' to me?} 15:25, 1 September 2013 (UTC)

Those vines look like muscadine/scuppernong, which is a New World native grape, and yes, is a weed insofar as the wild varieties can choke out desired garden plants. The grapes tend to not grow in large bunches, but rather as small individual grapes along the vine, perhaps in small bunches, but not in the traditional pyramidal grape bunches you expect from European wine grapes. We have them all over the edge of the woods along our property in North Carolina. I've been successful, so far, at keeping them out of my gardens. --Jayron32 19:00, 1 September 2013 (UTC)

Habits

I forgot the name of a condition where sufferers act in odd ways; such as excessively cleaning your hands, a need to position objects in a very specific way, etc. I think its obsessively compulsive disorder or something like that. Pass a Method talk 23:49, 31 August 2013 (UTC)

Obsessive-compulsive disorder. 86.141.185.189 (talk) 23:54, 31 August 2013 (UTC)