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Why Do Family Members Look Alike but Aren't Identical? Discover the Secrets of Human Genetics!

Have you ever wondered why family members share similar traits but aren't identical? This fascinating exploration of human genetics reveals how sexual reproduction promotes both continuity and variation among individuals. Through meiosis, a unique type of cell division, gametes (sperm and egg) are produced with reshuffled DNA, leading to an astounding 70 trillion combinations in each. With random fertilization playing a key role, the diversity of our genetic makeup becomes evident. Learn about inheritance, chromosome combinations, and what makes each of us unique!

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Why Do Family Members Look Alike but Aren't Identical? Discover the Secrets of Human Genetics!

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Presentation Transcript

  1. BIOL 106 Human Genetics and Health

  2. Family members look alike but not identical-why? (insert your family photo here)

  3. Here is the reason

  4. Sexual Reproduction Ensures Continuity With Variation • Meiosis-a special type of cell division that produces reproductive cells called gametes • Randomfertilization of egg + sperm

  5. A special type of cell division that reshuffles DNA of gametes

  6. Random Fertilization Gametes are called sperm and egg in humans. There is no real control over which sperm gets to the egg first.

  7. Meiosis and Gamete Production Take Place in the Gonads After meiosis, gonads have half the number of chromosomes as regular body cells. Chromosomes are reshuffled in meiosis: 246 combinations (about 70 trillion) Testicles produce around 85 million sperm each day. Ovaries produce 2 eggs each month. They are all products of reshuffling in meiosis.

  8. The “Average” Male Delivers Over 200 Million Sperm Cells Each Time

  9. The Number of Possible Combinations is VERY LARGE • 70 trillion possible chromosome combinations in sperm • 70 trillion possible chromosome combinations in egg • Any sperm can fertilize any egg • 70 trillion x 70 trillion • 490 plus 24 zeroes • 490,000,000,000,000,000,000,000,000

  10. Summary • You always inherit about half your DNA from each parent and share some chromosomes with your siblings: CONTINUITY • It is extremely unlikely that you will inherit exactly the same chromosomes as any sibling: DIVERSITY • These are the outcomes of meiosis + random fertilization = sexual reproduction.

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