From Seed to Seed:
Plant Science for K-8 Educators


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Genetic diversity revisited

Previously we talked about the importance of genetic diversity within a population of organisms, including the dangers of inbreeding and the benefits of a diverse gene pool.

Earlier, 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-you're different from each of the almost 6 billion other people on the earth!

This helps explain why each of us is unique. But it doesn't explain how all of 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.


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