STUDY GUIDE: Genetics

Note: If you are not absolutely sure what happens to chromosomes during meiosis you should review that before you begin this section on genetics.

KEY TERMS

1. F1 generation 2. F2 generation 3. P generation 4. Mendel's Laws 5. Laws of Probability 6. gene 7. dominant 8. recessive 9. locus 10. allele 11. homozygous 12. heterozygous 13. genotype 14. phenotype 15. Punnett square 16. monohybrid cross 17. dihybrid cross 18. trihybrid cross 19. test cross 20. incomplete dominance 21. codominance 22. multiple alleles 23. sex linked 24. autosome (=somatic chromosome) 25. sex chromosome 26. X chromosome 27. Y chromosome 28. Barr body 29. sex influenced traits 30. epistasis

31. pleiotropy 32. penetrance 33. expressivity 34. pedigree 35. sickle-cell disease 36. carrier 37. Huntington's disease 38. consanguineous mating 39. amniocentesis 40. polygenetic inheritance 41. Drosophila melanogaster 42. wild type 43. mutant phenotypes 44. chromosomal mutations 45. giant chromosomes 46. nondisjunction 47. autosomal abnormalities 48. trisomy 49. polyploid 50. Down's syndrome 51. sex chromosome disorders 52. hemophilia 53. Barr body 54. sex-linked trait 55. sex-influenced trait 56. Kleinfelter's syndrome 57. Turner's syndrome 58. super females 59. Nature vs. nurture 60. Linkage

QUESTIONS

1. Discuss Mendel's conclusions and relate them to the chromosomal theory of inheritance. Include comments on each of the following: Law of segregation, Law of independent assortment.

2. Differentiate between: dominant-recessive; allele-gene; homozygous-heterozygous; phenotype-genotype; monohybrid-dihybrid-trihybrid-etc.

3. What does it mean when we say a strain of organisms is "true breeding"?

4. What is a test cross?

5. Explain the inheritance of human ABO blood groups.

6. Describe and give an example of the following: pleiotropy, penetrance, expressivity and epistasis.

7. What are polygenetic traits?

8. Give two examples of dominant human genetic disorders.

9. Who is T.H. Morgan? What were his major contributions to genetics?

10. What does it mean if we say genes are linked? Which of Mendel's "laws" do linked genes break?

11. Explain linkage and show how crossover frequencies are used to make chromosome maps.

12. What kind of information is shown on chromosome maps?

13. Explain how sex is determined in humans.

14. Describe the X-Y, W-Z and haplo-diploidy systems of sex determination and give examples of each.

15. Discuss sex-linked inheritance in terms of X and Y chromosomes.

16. Explain gene dosage in terms of human female X chromosomes. Include in your description an explanation of what Barr bodies are.

17. What is aneuploidy(think about roots and prefixes- an, eu and ploidy)? Describe triploidy, and polyploidy.

18. Explain nondisjunction and tell how it affects chromosomal composition of cells.

19. Discuss chromosomal aberrations, including changes in individual chromosomes and alterations in chromosome number. Include in your discussion causes of these aberrations.

20. Explain how translocations, deletions, duplications and inversions alter chromosomal composition.

21. Describe the cause of Down syndrome.

22. Give five examples of human genetic diseases.

23. Distinguish between Turner's, Kleinfelter's and super female(metafemale) syndromes.

24. Explain why statistics is a useful genetic(or scientific) tool.

25. Explain why a large sample is more statistically reliable than a small sample?

26. Why is Drosophila such a good organism in which to study genetics?

A METHOD FOR DOING MENDELIAN CROSSES

1. Know the traits to be used.

2. Know how the alleles are expressed. Which is dominant, which is recessive, which is incomplete.

3. Establish a letter symbol for each trait. Use capital letters for dominant traits and small letters for the recessive allele.

4. Determine the genotypes of the parents. Keep in mind which traits are dominant and which are recessive when you do this.

5. Determine the gametes which are produced by the parents.

6. Combine the gametes. A Punnett square can be used.

7. Determine the genotype and phenotype ratios of the offspring.

TIPS FOR SOLVING GENETICS PROBLEMS

1. Only homozygous recessive genotypes express the recessive trait.

2. If an individual expresses a dominant trait that individual has AT LEAST one dominant gene.

3. If an intermediate condition or blending of traits is observed, expect codominance.

4. If a trait expresses itself mainly in males, suspect sex-linkage.

5. Monohybrid heterozygous crosses result in 3:1 phenotype ratios.

6. Dihybrid heterozygous crosses result in 9:3:3:1 phenotype ratios.