Re: The role of genetics in the developement and ossification of a bone

Well, genetics does have a major role to play in the growht processes of 
the body, including bones. Say, for example, in your family, both your 
parents or even if one of them is tall, then you have all the chances of 
being equally tall.
Ossification of bones is a part of the process of bone formation from 
cartilage. It begins in the embryo in-utero, and continues till all the 
ossification centres have fused by the age of 18 in girls and 21 in boys. 
A few variations in the years may occur. 

Look at the above image, which shows the various parts of a bone. The 
diaphysis is the shaft, the metaphysis is the lower end of the bone while 
the epiphysis is the joint forming part. We'll consider the femur (thigh 
bone) as our example. When a child is born, he has an ossification centre 
in the epiphysis and in the metaphysis as well. These centres look like 
white specks on an X Ray. The diaphysis has already been formed. As the 
child grows, the ossification centre slowly grows in size as more and 
more calcium is deposited. At the same time, genetics determines the 
amount of growth of the diaphysis, ie how long will it be. Once the child 
reaches puberty, there is a growth spurt, and subsequently, the 
ossification centres of the metaphysis and epiphyses fuse together. This 
fusion is the interplay of many hormones, which include growth hormone, 
oestrogens, etc. An excessive amount of these hormones may cause the 
centres to fuse prematurely, retarding growth, while, a deficiency might 
also retard growth with brittle bones. 
And this question might also come into your mind, that if till puberty, 
joints are part cartilage and part bone, then how do they sustain body 
weight, etc, then, well, that is one of the wonders of the human body!!!