Last week we talked about the importance of genetic diversity
within a population of organisms, including the dangers of inbreeding and the benefits of
a diverse genetic pool.In our earlier example, we
used a cell containing only two chromosomes. Most organisms, however, have more than two.
The average flowering plant has about 40 chromosomes, with each chromosome containing
hundreds of individual genes. And humans have an estimated 80,000 genes on their 46
chromosomes! Consider the HUGE number of possible gene combinations resulting from the
union of two human reproductive cells!
It is the built-in randomness during meiosis and the union
of gametes that accounts for most of the genetic variability among organisms. That’s
why your genetic blueprint is unique—different from each of the almost 6 billion
people on the earth!
This helps explain why each of us is unique. But it doesn't explain
how all the various traits came about. Why are there so many variations in hair and eye
color--or seed color? Sexual reproduction "shuffles the deck", but it doesn't
explain the existence of such diversity.
