Study Questions to Exam 4

Bio 1010, Section 04

Fall semester 2007

 

The Study Questions below are intended as a study tool. Write short answers to them using your lecture notes and textbook as references. After you have worked on them alone for awhile, I strongly recommend that you meet with other students in a study group to discuss the Study Questions and your answers. You may also raise these Study Questions in lecture and during meetings with me. Exam questions will be based on the correct and complete answers to the Study Questions.

Updated December 7, 2007

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1. What important events occur during interphase, prophase, metaphase, anaphase, and telophase of mitosis? What is cytokinesis?

 

2. Diploid and haploid are terms that describe how many sets of homologous chromosomes are present in a cell. Explain these terms. Which of your cells are diploid and which are haploid?

 

3. What are centromeres and kinetochores? When and where would you expect to find them in mitosis?

 

4. How do chromatids get moved into daughter cells appropriately during mitosis? What is the difference between a chromosome and a chromatid?

 

5. Meiosis makes four haploid cells from one diploid cell. How is this necessary sexual reproduction?

 

6. How does Meiosis I differ from Meiosis II?

 

7. Be able to recognize a definition ofthe following terms:

chromatid

homologous chromosome

centromere

kinetochore

centrosome

diploid

haploid

 

8. Most organisms are dipoid. What might the adaptive value of diploidy be?

 

9. How does Meiosis I differ from Meiosis II? When in Meiosis do crossing over and independent assortment occur?

 

10. Be able to recognize a definition ofthe following terms:

trait

allele

dominant allele

recessive allele

homozygous

heterozygous

phenotype

genotype

 

11. How does independent assortment combine Mom's genes with Dad's genes in your gametes? How does crossing over do the same thing but differently?

 

12. How does sexual reproduction contribute to genetic and phenotypic diversity in a population of organisms?

 

13. We discussed a hypothesis for the adaptive value of sex. What is it? How does sexual reproduction contribute to biological evolution?

 

14. For Mendel's peas, what made the dominant allele for purple flower color dominant over the recessive allele for white flower color?

 

15. What does a Punnett square do?

 

16. Presence or absence of a widow's peak in the human hairline is controlled by a single gene. The allele for a widow's peak is dominant. The allele for a straight hairline is recessive. A woman has a widow's peak and her husband does not. Neither of their two children have widow's peaks. What possible combinations of hairline alleles do the woman and her husband have? What combination of hairline alleles do their two children have? (Use a Punnett Square to answer).

 

17. In genetic experiments like Mendel's, what does a 3:1 ratio of 2 traits in the F2 generation indicate about the alleles for the trait? What does a 9:3:3:1 ratio for the combinations of two traits tell you about their alleles?

 

18. A person with type O blood has children with another person having type AB blood. What blood type alleles do these parents carry? What types of blood can they give or receive by transfusion and why? What blood types can their children have and with what probabilities?

 

19. A gene that contributes to male pattern baldness is on the X-chromosome. A man having this gene and showing male pattern baldness marries a woman with no male pattern baldness in her family. What is the probability that male children of this couple will exhibit male pattern baldness of the type carried by the father? A female child of this couple marries a man who does not show male pattern baldness. What is the probability that their male children will have the gene for male pattern baldness carried by their grandfather?

 

20. Meiosis in human males leads to four sperm cells. How many of these can lead to a male child? How many can lead to a female child? Explain.

 

21. What event during meiosis can lead to the trisomy 21 that confers Down's syndrome?

 

22. What is a karyotype? How would it allow you to see the sex of an unborm child? How would it allow you to know whether the unborn child had Down's Syndrome?

 

23. The Law of Segregation and the Law of Independent Assortment were derived from Mendel's work. In fact, these prinicples only apply to a small set of traits in most organisms. What criteria must hold for traits to exhibit Mendelian inheritance? Give examples of cases where traits do not exhibit Mendelian inheritance. How do Mendel's findings fit with what we now understand about meiosis?

 

24. What is a model organism? What made T.H. Morgan's flies a good model organism for the questions about inheritance that interested him?

 

25. What is a test cross? How can monohybrid test cross be used to confirm that a group of offspring from a previous cross of "true-breeding lines" are heterozygous? How can a dihybrid or trihybrid test cross be used to show that two genes are linked and do not exhibit independent assortment?

 

26. What are the differences between a linkage map, a cytogenetic map, and a physical map of the positions of genes on chromosomes?

 

27. If a mutation occurs in one of your skin cells, can that mutation be passed on to your children? If not, where would the mutation have to occur if it was to be passed on to your children?

 

28. Give a brief statement of the theory of biological evolution. What observations of living things does the theory of biological evolution try to explain?

 

29. Sexual reproduction is biologically costly and dangerous yet it is widespread among living things. What adaptive value of sex might offset its cost and risk? How does sexual reproduction contribute to biological evolution? How might asexual reproduction (cloning) yield a population that was vulnerable to extinction?

 

30. What processes can cause gene duplication? How might gene duplication contribute to the evolution of new genes by mutation?

 

31. Natural selection does not necessarily increase the complexity of organisms in a population. Explain this statement.

 

32. Natural selection does not ordinarily increase the genetic diversity of a population. Expalin this statement.

 

33. Compare and contrast phyletic versus divergent speciation. Which one leads to greater biodiversity?

 

36. How is reproductive isolation thought to contribute to speciation?

 

37. What is the evidence that mutations can be beneficial?

 

38. What is a "mass extinction"? Give an example of a mass extinction, including its possible cause.

 

40. The different races of the human species exhibit detectable physical difference and slight genetic differences. What allowed these differences to arise? What prevented the process of speciation from going any further?

 

41. What is "punctuated equilibrium"? How does it differ from "Darwinian gradualism"? How do the fossils of the early Cambrian period illustrate punctuated equilibrium?

 

42. The logistic growth equation accounts for the "carrying capacity" of an environment. What is meant by the carrying capacity?

 

43. The human death rate has decreased dramatically in the last 300 years. What caused this? What was the of this effect on human population growth? What is causing the growth rate to slow again in developed countries, e.g. in Europe?

 

44. The concentration of carbon dioxide in the atmosphere has risen from 270 parts per million (ppm) to 370 ppm since 1750. How do carbon dioxide and other greenhouse gases increase the retention of solar energy by the earth?