Secret of Life: Part III
Birth, Sex, & Death

1. What are all the cells in the body descended from?

From the fertilized egg.

2. When is the spinal cord formed?

During the first two weeks of pregnancy.

3. How long is the embryo when muscle blocks form?

When the embryo is about 1/4 inch long.

4. How are human cells different from chicken cells?

They same materials are used in both, but they are differently arranged in human and chicken.

5. How do cells know what to become?

Control genes tell them.

6. When are the chambers of the human heart completed?

When the heart is less than an inch long.

7. How do cells know where to go and what to do in the body?

Because they carry specific instructions with them in the genes.

8. What creature do scientists like to use for genetic testing?

Fruit flies.

9. What is the gene that activates other genes?

Control genes act like switches that turn other genes off and on.

10. Why did they start using zebra fish instead of fruit flies?

They are more like humans than the flies are.

11. Why do they breed so many zebra fish?

To get a large population so they can look for unusual mutations.

12. How many pairs of chromosomes are there?

23 pairs (46 total)

13. What letters made up the genetic code?

C, G, A, and T

14. What decides gender?

Normally, the X and Y chromosomes (XX=female, XY=male) but there are exceptions.

15. What gene did they use to change the gender of the mouse embryo?

The Sr-Y gene

16. How can a woman have XY genes or a man XX genes?

Because sex determination is controlled also by hormones and the Sr-Y gene.

17. Why did Christine look male at birth?

Due to an accidental production of male hormone produced by malfunctioning adrenal glands.

18. How did the Mexican Olympic authorities test for gender?

They used the Barr-body test, which involves scraping some cells from inside the cheeks.

19. Why was it difficult to test for an individuals gender genetically?

Because it is not conclusive - factors other than the genes can influence maleness and femaleness.

20. What gene did they think controlled aging?

The gene that causes Werner’s Syndrome, an inherited form of Ahlzheimers.

21. What proved that death is not directly caused by genes?

Identical twins, who have the same genes, die at different ages.

22. What happens after salmon reproduce?

Some species, which reproduce only once, die very soon after reproducing.

23. When does our body “abandon” us?

When we have ensured that our genes will make it into the next generation successfully.