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Name: Alice
Status: Student
Age: 13
Location: N/A
Country: N/A
Date: N/A 


Question:
What inheritance pattern does height follow? I think it is Polygenic, if so could you tell me why?



Replies:
Actually, height is what is called multifactorial. Not only are there many genes involved, such as genes for growth hormone, genes for the receptors on the outside of cells for growth hormone, genes for bone proportion, genes for the timing of the release of hormone and other growth factors; but there are also many interactions with the environment, including nutrition during gestation (while the mother was pregnant) and during the growth years, exposure to things such as cigarette smoke and alcohol before birth, birth order (generally second children are taller than first) and general health during the growth years. With all of these factors, it appears that we are born with a genetic potential for height (not all of the genes have been identified yet) and then the environment exerts its effects as we are growing.

Incidentally, I'm an adult woman who is 4 feet, 11 inches tall. My sons are 5 feet 8 inches and 5 feet 10 inches tall. Their father is 5 feet 9 inches tall. My children both exceeded what a children's growth specialist predicted for them when they were very young, and no one knows why!

Ellen Mayo


If height were controlled by a single gene and tall were dominant, then only two heights would be possible, tall and short. Even if height were incompletely dominant, in other words, being heterozygous blended the two other phenotypes, only tall, medium and short would be possible. This obviously isn't right. Height is under the control of more than one gene, perhaps many. It depends on how many active alleles you inherit from your parents. Lets say that height is controlled by 3 genes each with 2 alleles. So there are 6 possible active alleles, or alleles that actually contribute to height. Lets say that your father is medium tall or has 4 active alleles and two inactive. Lets say mom is medium and has 3 active and 3 inactive. Their children can have as many as 6 active alleles ( 3 from each) and be very tall. Or they can inherit as few as 5 inactive alleles and be quite short (although not as short as possible).

There is another factor to consider though, height is also a multi factorial trait-the environment has a role in determining your final height. Lets say that you were genetically programmed to be tall but you didn't have access to good medical care, had a poor diet and your mother smoked while she was pregnant. You may not reach your possible height. Boys have testosterone which increases muscle mass and bone growth more that estrogen does so boys usually are taller than girls. So, height is a complicated genetic factor.

van hoeck


I think height of humans develops in such a complex way that we do not understand all of it. As a rule of thumb, a child will be the size of the average of the parents, or slightly taller. But that may not be true for individual cases.Both Nature and Norture have a thing to say: both inheritance and other factors are important.

We know little about these other factors. People in Northern Europe are taller than in Southern Europe. Children in Northern Europe grow taller than their parents, and this has been going on for generations. The Dutch and Scandinavian people are now among the tallest in the world. But why? A balanced diet, healthy pregnancies, optimal medical child care, and high social standards result in more height. But even correcting for the absence of vitamin deficiencies and crippling diseases from the past, it is hard to explain why tweens are now few inches taller than the tweens of 20 years ago.

I don't know whether this is observed in other parts of the world as well. A Dutchman visiting Asia feels like a giant. My guess is that the genes dictate that this won't change in future.

Dr. Trudy Wassenaar (Dutch)


It is polygenic...we are fairly sure of this because of the inheritance patterns it follows...that is they are do not follow what would be typical from a single gene.

PF



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