End of Chapter 04 Questions

by Roger Bourke White Jr., copyright May 2018


1. If two people with blood type A, both with the AO genotype, have children, what proportion of their children would be expected to have blood type O? Understanding the underlying principles that allow you to answer this question could potentially be relevant to you personally. How?

2. Why are the principles of segregation and independent assortment key to understanding inheritance? How do these principles differ from the theory of blending inheritance?

3. Sickle-cell anemia is frequently described as affecting only African or people of African descent; it's considered a "racial" disease that doesn't affect other populations. How would you explain to someone that this view is incorrect?

4. Give some examples of how selection, gene flow, genetic drift, and mutation have acted on populations or species in the past. Try to think of at least one human and on nonhuman example. Wy do you think genetic drift might be important today to endangered species?


1. About 25% will be type O. The other 75% will have at least one A genotype and type A blood. These are relevant if I'm planning on having children. What genotypes they will have are 50% dependant on me. A further thought: this percentage could change in the near future. It will change if we do genetic testing on zygotes and decide which ones to let grow and which ones to toss away.

2. Blending is the concept that a child's traits are simply a mix of the parent's traits. Segregation is about genes, and the concept that just one gene, one from either parent, will determine the child's trait in that allele.

3. Sickle-cell anemia is an adaptation to an environment filled with chronic malaria. It happens that sub-Saharan Africa is filled with malaria so when this mutation happened there it thrived. It is racial in the same sense that pale skin serves well in an environment where a person gets little exposure to sunshine so they can't get much Vitamin D created by sun shining on skin.

4. Gene flow: when genes move between populations, but not the individuals. The book example of soldiers leaving children in a foreign land is a good one, and common. Another legendary example is gypsies taking chickens and leaving daughters with very surprised parents. Genetic drift: this is when the gene pool in a small isolated population changes and become a little different from that of other populations around it or in other places in the world. Polynesians are an example in the human genotype. Mutation: these are spontaneous changes to the allele in an organism. If they are harmful they die out quickly because the organism dies quickly and without children. If they are beneficial they can spread if the organism has lots of successful children.



--The End--