UC has a genetic (not hereditary) component so your son had the UC gene in his system and whatever factor (biological or envrionmental) triggered it is unknown.
Genes are tiny particles that determine all hereditary
traits. They are carried on the chromosomes. Each
chromosome bears hundreds of genes, arranged in a line
along its length. Every person inherits two genes for a
particular trait -- one from his/her mother and one from
his/her father. But in many traits, the action of one gene
completely overpowers the action of the other. The powerful
gene is called dominant and the other recessive. For
example, suppose a dark-haired father and a red-haired
mother have a dark-haired child. In this case, each of the
child's cells contains a gene for dark hair and a gene for
red hair. But because the child has dark hair, it is
apparent that the gene for dark hair is dominant over the
gene for red hair.
Recessive genes do not visibly show up when there is a
dominant gene present. A hybrid is a person who has both a
dominant and recessive gene. Their appearance is that of a
person who has no recessive gene, but they carry the
recessive gene, and it is possible their children will also.
There are also times when there is a compromise. If two
genes are both dominant, the resulting offspring will have
a blend of those genes. For example, a black rooster and a
white hen mate, and the resulting offspring are gray. The
same can be said for people.
Genes are made of deoxyribonucleic acid, or DNA for short.
DNA is a threadlike molecule with a diameter of only about
one ten-millionth of an inch. The thread is actually
double, and resembles a tiny twisted rope ladder. A DNA
molecule contains two kinds of purine bases. They are
adenine (called A) and guanine )called G). It also contains
two kinds of pyrimidine bases called cytosine (C) and
thymine (T). A and T fit together and C and G fit together.
No other combinations work. In other words, there are only
four kind of base-pair combinations in a DNA ladder: A-T
and C-G, or T-A and G-C. All genes in every cell contain
these same four bases, A, T, C, and G. The difference
between one gene and another lies in the arrangement of
pairs of bases along the DNA molecule. There are at least
several hundred pairs of bases in each gene. For this
reason, a vast number of arrangements is possible, and
countless kinds of genes can be formed.
Another aspect of genetics is mutation. A gene is an
extremely stable structure. It may remain stable through
thousands of generations, copying itself correctly in
between each cell division. Occasionally, however, a
mistake occurs in the copying process. This mistake may
upset the ordered sequence of base-pairs in a gene and
cause a mutation.
Some mutations are helpful and may change an animal or
plant so that it is better equipped to live in its
surroundings. For example, once ducks had no webbing on
their feet. Only mutant ducks had webbing at the time. The
mutant ducks were better swimmers, so they survived attacks
from predators while ducks without webbing did not. Thus
only ducks with webbed feet survived, and we have the