Actually, you CAN get a “blend,” even if it seems to outward appearances that only the dominant gene is being expressed. People who are “healthy carriers” of sickle-cell anemia, for example, actually have a mix of normal red blood cells AND sickle-shaped cells circulating in their bloodstream. The dominant normal gene codes for the production of normal hemoglobin, thus making normal blood cells, but it doesn’t SUPPRESS the activity of the recessive sickle gene, which goes right on coding for defective hemoglobin resulting in sickle-shaped cells.
And the comments seem to be assuming that the horizontal stripe gene is the same gene that produces the vertical strip gene. They could well be two different genes entirely, not even on the same chromosome, the SGP (Shirt Genome Project), unlike it better known cousin the HGP, is sorely in need of funding and hasn’t even begun to map the stripe genes.
Throbert McGee: Actually, you CAN get a “blend,” even if it seems to outward appearances that only the dominant gene is being expressed. People who are “healthy carriers” of sickle-cell anemia, for example, actually have a mix of normal red blood cells AND sickle-shaped cells circulating in their bloodstream. The dominant normal gene codes for the production of normal hemoglobin, thus making normal blood cells, but it doesn’t SUPPRESS the activity of the recessive sickle gene, which goes right on coding for defective hemoglobin resulting in sickle-shaped cells.
I wonder about the concept of “dominance” in the instance of normal (homozygous) and sickle cell trait (heterozygous) and sickle cell anemia (homozygous). Only if there is no manifest difference in phenotypes between the homozygous and heterozygous genotypes is it a matter of truly “dominant” and “recessive” genes, or at least that’s my understanding of Mendelian genetics.
Incomplete dominance maybe? Hey, it works for snapdragons.
Alternatively, maybe vertical stripes are one set of genes and horizontal are another set of genes. Just like the child of an ugly woman and a stinky man can be both ugly and stinky.
Nah, post-Mendelian genetics support the result just fine
Assume we have two genes here, H for horizontal stripes, V for vertical. Assume that the gene for stripes in both cases is dominant, and the one for no stripes is recessive. Finally, assume both parents are homozygous.
Then, in this case, the father has HHvv, and the mother has hhVV. Their child would then have the heterozygous HhVv, and display stripes in both directions . . . which, in fact, is the case. The child, crossed with another doubly-heterozygous person, would have children of the patterns:
HHVV – Striped both ways
HHVv – Striped both ways
HHvV – Striped both ways
HHvv – Striped horizontal only
HhVV – Striped both ways
HhVv – Striped both ways
HhvV – Striped both ways
Hhvv – Striped horizontal only
hHVV – Striped both ways
hHVv – Striped both ways
hHvV – Striped both ways
hHvv – Striped horizontal only
hhVV – Striped vertical only
hhVv – Striped vertical only
hhvV – Striped vertical only
hhvv – Unstriped
For 9 double-striped, 3 horizontal-striped, 3 vertical-striped, and 1 unstriped granchild.
I agree, you can come up with assumptions that make it fit and even rare cases of incomplete dominance but it’s not a very good illustration of “How Genetics Works” for the poor Bio 101 students.
Phil: I agree, you can come up with assumptions that make it fit and even rare cases of incomplete dominance but it’s not a very good illustration of “How Genetics Works” for the poor Bio 101 students.
Exactly. It is like showing the schematic of a flea flicker with the heading “What a QB does”.
But also notice the footgear: Dad looks to be wearing flip-flops, Mom looks to be wearing sandals with a strap, and the kid seems to have a combo of the two. This is very clever.
Blood types are weird anyway. I’m AB, my husband is O, so I think that means our daughter is either A or B.
My mom says our daughter is a pretty girl (true) and that she looks like her dad (very true) and that she’d always heard, if you want to see a pretty little girl, follow an ugly man home.
People with sickle cell trait have completely normal red blood cells. About 40% of their hemoglobin is of the sickle type, but the RBC sickling in sickle cell DISEASE occurs because low-oxygen conditions cause sickle hemoglobin to polymerize. Unless a very high proportion of a cell’s hemoglobin is of this “hemoglobin S” type, the polymerization reaction is held in check and the cells never sickle.
Not strictly relevant, since the previous commenter’s point still stands (a combination of different traits can actually occur even in classically Mendelian recessive-gene inheritance), but I couldn’t bear the thought of VC readers thinking sickle trait carriers have abnormal blood cells. (It’s an important concern.)
T’is sleeping sickness Laura. Only people with round blood cells can get it, if you have one sickle-cell gene you don’t have sickle-cell anemia (blood cells so far from round that they have difficulty transporting oxygen) but your blood cells are far enough from being round that you are unaffected by sleeping sickness. Or so the theory was many moons ago when I took that genetics class.
The reason learning to ride a bike is tricky is that there is a counter intuitive aspect to it that nobody realizes they are doing. If people could and would just tell kids how to ride, then it would be easy for them to learn.
The first thing one needs to learn is how to balance. It’s not very hard for kids to figure out on their own but it’s even easier if someone tells them. The trick is simply to turn the handlebars the direction you start to fall. If your bike starts to lean to the right then turn the handlebars to the right and that will bring you back upright and into balance (you have to be moving forward for it to work and if you’re going to slow it makes it harder). It’s best to learn this in a giant flat area so that as you’re turning the handlebars left and right, learning to balance, you don’t have to worry about where you’re going and running into anything. The narrowness of the typical residential street makes this challenging.
The second thing you need to know, and the counter intuitive part that is hard for the brain to figure out, is how to make the bike go the direction you want it to go. It’s called counter steering. This is so counter intuitive that people rarely even believe me when I explain it to them. It’s true though. It’s in the California Department of Motor Vehicles Motorcycle Handbook, there’s a web page by a Berkley physics professor, I’ve seen articles about it in a major motorcycle magazine. This is not controversial. Nobody who is an expert in motorcycle or bicycle physics will contradict me. The trick to turning a bicycle or motorcycle is to turn the handlebars the opposite direction you want to go. Seriously, I’m not joking. You don’t hold them there. A little jerk the opposite way will suffice.
For example, say you’re riding along perfectly straight. You’ve managed to get yourself so that your bike and your body is perfectly straight up and down and balanced and your handlebars are straight ahead. Now say you decide to turn LEFT. The first thing you do is give the handlebars a little nudge to the RIGHT. Your body continues in a roughly straight ahead direction while your bike moves out from underneath you to the right. Now you are leaning to the left just as you want to be and need to be in order to do the left turn you want to make. Now that you are leaned to the left you can proceed to turn the handlebars to the left and carry out your left turn.
Note that this IS how YOU ride a bike even if you don’t realize it. There is no other way to do it. Some people think that in order to initiate a turn they just lean. But the only way you can lean your bike is to turn the handlebars the opposite way you want to lean. If you try to just lean your body by doing something like just bending your waist to the side, then your upper body will lean the way you want, but you have nothing to push against so the equal and opposite reaction will cause your lower body and your bike to lean the opposite way and cancel out nearly all of your lean. To prove that you can’t just lean, try sitting on your bike with it not moving forward and try to balance it with your feet off the ground. It’s extremely difficult. But if you’re moving forward, you can turn the handlebars to make your bike go out from underneath you to effect a lean, and it’s easy to balance.
One reason people don’t realize that they’re doing this counter steering thing is that when you’re riding a bike you’re constantly turning your handlebars back and forth and back and forth (a little tiny bit) in order to stay balanced. When you decide to make a turn your brain subconsciously just turns the handlebars a little bit earlier and a little bit more than it was going to in the course of maintaining balance anyway. It’s like you’ve just willed yourself to lean but really you’ve done a little counter steering without even realizing it.
I feel sorry for all the kids who break their legs and scrape their knees and crack their heads needlessly just because nobody was there who could tell them how to ride their bike. Their brains had to subconsciously figure out how to counter steer and balance at the same time. I think teachers should be educated and schools should be required to teach bike riding in order to save kids the injuries.
But there’s another reason that people need to know consciously about counter steering. When you need to make a hard fast turn in an emergency, a little subconscious nudge isn’t enough. You have to turn the handlebars hard and far in the opposite direction you want to go in order to make a fast and steep lean in preparation for your hard fast turn. It has been observed that motorcyclists often turn directly towards the objects they’re trying to steer away from in emergencies. For example if a motorcyclist is driving down the middle of the right hand lane of a road like normal (in the US), and a car pulls halfway into the lane and stops, so that the motorcyclist would just hit the front bumper if he continued straight, instead of turning to the left to go around the front of the car, motorcyclists will often turn right and hit the middle or rear of the car. This is caused by the motorcyclist quickly yanking the handlebars to the left to go around the front of the car. The result of turning the handlebars left is a right lean and a right turn. When you want to make a quick hard turn you have to yank the handlebars quick and hard the opposite way you want to go. If you don’t know that or you think that’s not true then you may die.
I place this post in the public domain so that this important info might save some kids and some motorcycle riders from injury.
Sheesh. Kids these days, learning to ride their bikes on city streets. They don’t even know. Back in my day, we didn’t get to practice before we went up on the high wire. I had to learn 120 feet in the air while wearing a clown nose and a tutu, with Hogo the Dancing Kodiak looking up at me, licking his chops. Uphill both ways. Snowing!
Nobody told me how to ride. Just told me, if I fell, to play dead in case Hogo was hungry.
Don’t be fooled by the photo. The three subjects in the photo aren’t family at all but actually are all Barnum and Bailey circus freak show performers. The guy on the left is “The Elephant Man” and the two ladies on the right are actually “The bearded Lady” and her lesbian friend “The World’s Smallest Lady.” The photo was taken from the rear for commercial reasons.
Blood types are weird anyway. I’m AB, my husband is O, so I think that means our daughter is either A or B.
My wife (HS bio teacher) learned the hard way not to have kids do genetics problems (blood type, attached/detached earlobes, etc) using the actual traits of student and parents. It’s really awkward when the genetics point to different parents than expected…
S, since we are picking nits, incomplete dominance, however rare, is still genetics.
I read somewhere that blood type can actually be affected by bacteria to which the fetus develops antibodies. Maybe we learned that in my micro class 5 years ago. So it seems that some of the paternity tests that used to be done, that relied on blood type, could have given a wrong answer.
I think it’s now recognized that blood type tests can’t determine paternity and we will just have to disagree that there is a nit, here, since I view the title as misleading.
Phil says:
Na. After Mendel, we know that the dominate phenotype or the recessive phenotype would show in the next generation not some mix.
February 25, 2010, 5:22 pm1040 says:
I think this is a pre-Mendelian understanding of genetics. Didn’t know the Volokh Conspiracy was that conservative!
February 25, 2010, 5:38 pmArthur Kirkland says:
Enough with the elitist technobabble. Where are the dinosaurs?
February 25, 2010, 5:39 pmPhil says:
1040, Perhaps it’s an originalist understanding of genetics because Mandel was not yet born at the time of the founding.
February 25, 2010, 5:43 pmSyd Henderson says:
Codominant genes.
February 25, 2010, 5:45 pmThrobert McGee says:
Actually, you CAN get a “blend,” even if it seems to outward appearances that only the dominant gene is being expressed. People who are “healthy carriers” of sickle-cell anemia, for example, actually have a mix of normal red blood cells AND sickle-shaped cells circulating in their bloodstream. The dominant normal gene codes for the production of normal hemoglobin, thus making normal blood cells, but it doesn’t SUPPRESS the activity of the recessive sickle gene, which goes right on coding for defective hemoglobin resulting in sickle-shaped cells.
February 25, 2010, 5:50 pmLTR says:
Probably the only blog I read whose readership will generally get the point of this in 30 seconds or less.
February 25, 2010, 5:53 pmrequired says:
Well played or well plaid if you prefer.
And the comments seem to be assuming that the horizontal stripe gene is the same gene that produces the vertical strip gene. They could well be two different genes entirely, not even on the same chromosome, the SGP (Shirt Genome Project), unlike it better known cousin the HGP, is sorely in need of funding and hasn’t even begun to map the stripe genes.
February 25, 2010, 5:54 pmneurodoc says:
I wonder about the concept of “dominance” in the instance of normal (homozygous) and sickle cell trait (heterozygous) and sickle cell anemia (homozygous). Only if there is no manifest difference in phenotypes between the homozygous and heterozygous genotypes is it a matter of truly “dominant” and “recessive” genes, or at least that’s my understanding of Mendelian genetics.
February 25, 2010, 6:00 pmS says:
You always get a blend of genes from the parents. Phenotype, however, refers to what appears on the outside (pheno, meaning show).
February 25, 2010, 6:01 pmDennis N says:
Nothing to do with genetics. It’s Intelligent Dressing.
Or the opposite.
February 25, 2010, 6:01 pmegd says:
Incomplete dominance maybe? Hey, it works for snapdragons.
Alternatively, maybe vertical stripes are one set of genes and horizontal are another set of genes. Just like the child of an ugly woman and a stinky man can be both ugly and stinky.
February 25, 2010, 6:01 pmD.R.M. says:
Nah, post-Mendelian genetics support the result just fine
Assume we have two genes here, H for horizontal stripes, V for vertical. Assume that the gene for stripes in both cases is dominant, and the one for no stripes is recessive. Finally, assume both parents are homozygous.
Then, in this case, the father has HHvv, and the mother has hhVV. Their child would then have the heterozygous HhVv, and display stripes in both directions . . . which, in fact, is the case. The child, crossed with another doubly-heterozygous person, would have children of the patterns:
HHVV – Striped both ways
HHVv – Striped both ways
HHvV – Striped both ways
HHvv – Striped horizontal only
HhVV – Striped both ways
HhVv – Striped both ways
HhvV – Striped both ways
Hhvv – Striped horizontal only
hHVV – Striped both ways
hHVv – Striped both ways
hHvV – Striped both ways
hHvv – Striped horizontal only
hhVV – Striped vertical only
hhVv – Striped vertical only
hhvV – Striped vertical only
hhvv – Unstriped
For 9 double-striped, 3 horizontal-striped, 3 vertical-striped, and 1 unstriped granchild.
February 25, 2010, 6:03 pmPhil says:
I agree, you can come up with assumptions that make it fit and even rare cases of incomplete dominance but it’s not a very good illustration of “How Genetics Works” for the poor Bio 101 students.
February 25, 2010, 6:09 pm1040 says:
Exactly. It is like showing the schematic of a flea flicker with the heading “What a QB does”.
February 25, 2010, 6:23 pmAnym_Avey says:
In light of the thread’s current direction, maybe we could explore the genetic determinants of autism spectrum disorders?
February 25, 2010, 6:40 pmptt says:
Further down the pier, circling the hot dog wagon.
February 25, 2010, 6:52 pmArthur Kirkland says:
Thanks. I see them now. Just checking to make sure this is suitable for Texas schoolchildren.
February 25, 2010, 6:57 pmrjb9 says:
Wait, which “Sarah P.” pointed this out to you? Someone tell Andrew Sullivan!
February 25, 2010, 7:11 pmHarry Schell says:
I put it out to friends and acquaitences via email as the instructional message of the day.
Hilarious, and so necessary today.
February 25, 2010, 7:18 pmJeff says:
But also notice the footgear: Dad looks to be wearing flip-flops, Mom looks to be wearing sandals with a strap, and the kid seems to have a combo of the two. This is very clever.
February 25, 2010, 7:46 pmBruce Hayden says:
Not sure I would want to go to a family reunion with this family. The visual effect would likely be a bit overwhelming.
February 25, 2010, 7:48 pmAnonsters says:
LOL.
February 25, 2010, 8:02 pmSyd Henderson says:
egd says:
Syd Henderson: Codominant genes.
Incomplete dominance maybe? Hey, it works for snapdragons.
I was thinking of ABO blood types.
February 25, 2010, 8:24 pmLaura(southernxyl) says:
Blood types are weird anyway. I’m AB, my husband is O, so I think that means our daughter is either A or B.
My mom says our daughter is a pretty girl (true) and that she looks like her dad (very true) and that she’d always heard, if you want to see a pretty little girl, follow an ugly man home.
For what that’s worth.
February 25, 2010, 8:30 pmys says:
You, genetics gurus, tell me where the 90 degrees rotation of the striping comes from.
February 25, 2010, 8:31 pmHow Genetics Works: | Liberal Whoppers says:
[...] the original here: How Genetics Works: [...]
February 25, 2010, 9:39 pmMM says:
People with sickle cell trait have completely normal red blood cells. About 40% of their hemoglobin is of the sickle type, but the RBC sickling in sickle cell DISEASE occurs because low-oxygen conditions cause sickle hemoglobin to polymerize. Unless a very high proportion of a cell’s hemoglobin is of this “hemoglobin S” type, the polymerization reaction is held in check and the cells never sickle.
Not strictly relevant, since the previous commenter’s point still stands (a combination of different traits can actually occur even in classically Mendelian recessive-gene inheritance), but I couldn’t bear the thought of VC readers thinking sickle trait carriers have abnormal blood cells. (It’s an important concern.)
February 25, 2010, 9:43 pmLaura(southernxyl) says:
But per the malaria theory, there’s something different about sickle cell trait people’s blood, right?
February 25, 2010, 9:56 pmrequired says:
T’is sleeping sickness Laura. Only people with round blood cells can get it, if you have one sickle-cell gene you don’t have sickle-cell anemia (blood cells so far from round that they have difficulty transporting oxygen) but your blood cells are far enough from being round that you are unaffected by sleeping sickness. Or so the theory was many moons ago when I took that genetics class.
February 25, 2010, 10:04 pmAuren Kir says:
The horror!
February 25, 2010, 10:19 pmAvid reader, reluctant poster says:
Sorry, geneticists. I couldn’t resist.
February 26, 2010, 12:20 amTatterdemalian says:
Black stripes are dominant genes, white stripes are recessive genes.
February 26, 2010, 8:53 amNecromancer EXE says:
LOL!!!
February 26, 2010, 9:09 amI´m impressed how this picture shows something that usually needs a boring 5-hours class in the most simple way!!!
^O^
JMA says:
Sheesh. Kids these days, learning to ride their bikes on city streets. They don’t even know. Back in my day, we didn’t get to practice before we went up on the high wire. I had to learn 120 feet in the air while wearing a clown nose and a tutu, with Hogo the Dancing Kodiak looking up at me, licking his chops. Uphill both ways. Snowing!
Nobody told me how to ride. Just told me, if I fell, to play dead in case Hogo was hungry.
February 26, 2010, 10:45 amTim H says:
Don’t be fooled by the photo. The three subjects in the photo aren’t family at all but actually are all Barnum and Bailey circus freak show performers. The guy on the left is “The Elephant Man” and the two ladies on the right are actually “The bearded Lady” and her lesbian friend “The World’s Smallest Lady.” The photo was taken from the rear for commercial reasons.
February 26, 2010, 11:08 amJohn Moore says:
Absolute thread win!
required says:
Nope, Malaria.
February 26, 2010, 9:59 pmscience fail says:
Wow. Mega science fail on this post. If there’s one thing Mendelian inheritance described, this is NOT how genetics works.
February 26, 2010, 10:19 pmLaura(southernxyl) says:
Is it not kind of like crossing red and white four o’clocks and getting pink? Or an orange cat and a black cat producing a calico kitten?
February 26, 2010, 10:33 pmThe Grey Man says:
I’m not surprised you racist conservatives are obsessed with those black stripes when you should be thanking Al Gore for inventing genetics.
(sarc, of course!!)
February 26, 2010, 11:56 pmS says:
Then it should be entitled: “How Rare Incomplete Dominance Looks in the First Generation.” Not the present title.
February 27, 2010, 9:46 amPintler says:
My wife (HS bio teacher) learned the hard way not to have kids do genetics problems (blood type, attached/detached earlobes, etc) using the actual traits of student and parents. It’s really awkward when the genetics point to different parents than expected…
February 27, 2010, 10:43 amElsa says:
@LTR That is exactly what I’m thinking.
I don’t understand about all the scientific stuff, but I think this post is very efficient :-)
February 27, 2010, 5:03 pmLaura(southernxyl) says:
S, since we are picking nits, incomplete dominance, however rare, is still genetics.
I read somewhere that blood type can actually be affected by bacteria to which the fetus develops antibodies. Maybe we learned that in my micro class 5 years ago. So it seems that some of the paternity tests that used to be done, that relied on blood type, could have given a wrong answer.
February 28, 2010, 9:31 amMarie says:
Are we sure both of the adults shown are really the child’s parents? If so,where did the hat gene come from?
February 28, 2010, 11:11 amS says:
I think it’s now recognized that blood type tests can’t determine paternity and we will just have to disagree that there is a nit, here, since I view the title as misleading.
February 28, 2010, 2:36 pmDavid says:
Doesn’t anybody here have a sense of humor? Or are you all so subtle that you’re pretending to take a joke seriously.
February 28, 2010, 6:45 pmscience fail says:
so.. a basic error in understanding is now a nit? next post: how babies are made with jesus being the illustrative example.
February 28, 2010, 9:54 pmlinks for 2010-02-28 « weblinkstream says:
[...] The Volokh Conspiracy » Blog Archive » How Genetics Works: (tags: FunImages fromemail) [...]
March 1, 2010, 12:03 am