SINGLE NUCLEOTIDE POLYMORPHISMS. I had always thought that there were only a few genes which affected height. I assumed, if I thought about it, that a person’s height would be some kind of average of the heights of their parents and perhaps their grandparents. I suppose you could say that my understanding was not much beyond that of Mendel. I believed all that until I read the article about Shawn Bradley a few days ago and found out the role of Single Nucleotide Polymorphisms.
What are single nucleotide polymorphisms (SNPs)? Here is an explanation (quoted at length) from the US NATIONAL LIBRARY OF MEDICINE:
“Single nucleotide polymorphisms, frequently called SNPs (pronounced “snips”), are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA.”
“SNPs occur normally throughout a person’s DNA. They occur once in every 300 nucleotides on average, which means there are roughly 10 million SNPs in the human genome.”