Genetics I
Exam 3 Review Sheet
NOTE: These are just some of the important aspects presented for Test #3 that you should
be familiar with. This Review Sheet DOES NOT represent all material that could be
covered on the Exam. This Review Sheet is to help guide you in your preparation for the
Exam. Be sure to fully study your class notes, slides (lectures 10-14), outside readings
(Animal Sexuality, Zeroing in on the Sex Switch, Drosophila melanogaster video script),
workbook (pages 126-179), and text book. Especially take time to work all example
problems in the workbook.
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4.
Understand the differences between Mitosis and Meiosis.
Contrast the terms tetrad and bivalent when discussing chromosomes.
What is a tetrad, a dyad, and a monad when discussing chromosomes in Meiosis?
Describe the events that occur during the specific stages of Prophase I:
a. Leptotene
b. Zygotene
c. Pachytene
d. Diplotene
e. Diakinesis
5. What are cross-over events? Why are they important? Do cross-over events occur
between sister chromatids or between non-sister chromatids?
6. During which stage of Prophase I do cross-over events occur? During which stage of
Prophase I are the cross-over events visualized as chiasmata?
7. Describe what is meant by the saying “slipping off the ends.”
8. Are Meiosis I and II reductional division and/or equational division?
9. Does pairing of homologous chromosomes occur during Meiosis I, Meiosis II, and/or
during Mitosis?
10. DNA has been packaged into the loop packaging stage during interphase and progresses
to a rosette packaging by the Leptotene stage of Prophase I. What extent is the DNA
packaged by the Pachytene stage of Prophase I?
11. N = the number of complete sets of chromosomes or the gene (allele) complement
number and C = Amount (mass) of DNA in the nucleus. Describe how the values of N
and C change during Mitosis and during Meiosis I and Meiosis II.
12. Contrast the two models explaining chromosome separation: Traction Fiber vs. Pac-man.
13. Where in the testes does spermatogenesis primarily occur?
14. Where does oogenesis occur?
15. Place the following terms in order of progression of spermatogenesis:
a. Spermatid, Secondary Spermatocyte, Sperm, Spermatogonium, Primary
Spermatocyte
b. When does the first meiotic division occur? When does the second meiotic
division occur? Ex: Which division occurs between the Primary and Secondary
Spermatocyte?
16. Place the following terms in order of progression of oogenesis:
a. Primary Oocyte, Oogonium, First Polar Body, Second Polar Body, Ovum (Egg),
Secondary Oocyte, Ootid
b. When does the first meiotic division occur? When does the second meiotic
division occur?
c. When are the first and second polar bodies formed? In mammals, what triggers
the formations of the first and second polar bodies?
17. What three changes occur when a spermatid differentiates into a mature sperm?
18. What is the acrosome reaction? Why is it important for sperm?
19. What is the importance of the zona reaction and the vitelline block during fertilization?
20. Which parts of a flower are the male structures? Which parts are the female structures?
21. What is the micropyle in the female part of a flower?
22. Does a diploid microspore mother cell undergo meiotic divisions to become a pollen
grain or an egg during sporogenesis?
23. Why does a pollen grain have two haploid nuclei? What is the purpose of each nuclei?
24. One of the two nuclei in the pollen grain divides again to produce two male gametes.
What nuclei do each of these two male gametes unite with in the female embryo sac?
25. Of the four haploid megaspores that are formed from the diploid megaspore mother cell,
how many survive? What happens to the surviving megaspore(s)?
26. Describe the fates of the following nuclei in the embryo sac of the female part of a
flower: antipodals, polar nuclei, synergids, egg.
27. Explain why the endosperm is 3n after fertilization. What is the purpose of the
endosperm?
28. What are the two main theories of sex determination?
29. What are the two types of chromosomes?
30. What is the genotype of a normal human male? What is the genotype of a normal human
female?
31. How many autosomes and how many sex chromosomes do humans have? Chickens?
Drosophila melanogaster?
32. Is the X or the Y chromosome larger?
33. In mammals, a normal male is the heterogametic sex and a normal female is the
homogametic sex. Define heterogametic and homogametic. Which sex is heterogametic
in birds (such as chickens)?
34. What is the genotype for a person with Turner’s syndrome? Is this individual male or
female? Are they sterile or fertile?
35. What is the genotype for a person with Klinefelter’s Syndrome? Is this individual male
or female? Are they sterile or fertile?
36. How is protenor sex determined? What is the sex of a protenor with 1X? With 2X?
37. How is chicken sex determined? What is a rooster’s genotype? What is a hen’s
genotype?
38. List examples of external stimuli that can determine sex in Environmental Sex
Determination. List the example of internal stimuli that can determine sex.
39. Bonellia veridis the Green Spoonworm has Environmental Sex Determination. Describe
what would cause a larva to differentiate into a male. What allows larvae to become
female?
40. Horsetail plant gametophytes sex is also determined by the Environment. Which sex
predominates during good growth conditions? The other sex predominates in poor
growth conditions.
41. Cucumber and muskmelon will produce female flowers with exposure to what chemical?
Hint: This chemical is also a gas given off by rotting or ripening fruit.
42. Many reptile species, including Alligator mississippiensis, exhibit a type of
Environmental Sex Determination known as Temperature Dependent Sex Determination.
Describe Temperature Dependent Sex Determination.
43. Honey bees that hatch from a fertile egg are females and bees that hatch from an
unfertilized egg are males. What term describes when unfertilized eggs become activated
and develop into viable individuals as part of the normal life cycle? What other animals
have been found to exhibit this phenomenon?
44. There are several types of parthenogenesis. Please describe facultative and automictic
parthenogenesis.
45. What sex are parthenogens in birds? What sex are mammalian parthenogens?
46. In the Calvin Bridges model for sex determination in Drosophila melanogaster, how
many autosomes are represented by the letter A? Understand how to represent male and
female genotypes using this method with the 8 total chromosomes in the fruit fly.
47. The Calvin Brides model shows how sex is determined based on the ratio of X
chromosomes to the number prior to A. Write the values to get a metafemale, a fertile
female, an intersex fly, a fertile male (don’t forget the Y chromosome), and a metamale.
48. Define nondisjunction. What is the implication of a nondisjunction event during
Anaphase I?
49. Define Aneuploid, Euploid, and Polyploid.
50. A human embryo begins with a bipotential gonad (able to differentiate into either the
male or the female reproductive tract). Describe the role of the genes SRY and DAX1 in
directing the bipotential gonad to differentiate into the male or female reproductive tract.
51. The embryonic Mullerian Duct becomes the male or female reproductive tract (circle
one). The embryonic Wolffian Duct becomes the male or female reproductive tract
(circle one).
52. What hormone/substance causes regression of the Mullerian duct?
53. What is the function of the p450 aromatase gene?
54. What could happen in a male organism if the male sex hormones controlling secondary
sex characteristics (testosterone, dihydrotestoterone) are not produced and secreted?
55. What is the Mary Lyon Hypothesis?
56. What are Barr bodies? Do Barr bodies occur in somatic and/or reproductive cells?
57. How do you calculate the number of Barr bodies in an organism?
58. Define Hemizygous.
59. Why are normal calico cats always female?
60. To get a male calico cat, what would his genotype have to be? What aneuploid condition
is this in humans?
61. Define Gynandromorph. What is a bilateral gynandromorph?
62. Define Chimera.
63. What is a Hermaphrodite?
64. What is a Free Martin in cattle?
65. Describe the difference between sex-influenced and sex-limited gene expression.
66. What is a reciprocal cross? What is the purpose of doing a reciprocal cross? How do you
know if a trait is sex-linked or not?
67. Define sex-linkage.
68. Is fruit fly red and white eye color a sex-linked trait? Is fruit fly normal and vestigial
wing type a sex-linked trait?
69. How can you distinguish a male fruit fly from a female fruit fly?
70. What cross in chickens will produce offspring that can be distinguished by sex at hatch
just by looking at the down (feather) color in the chicks?
71. What is a holandric gene? Give an example of a holandric trait.
72. Understand that sex-influenced and sex-limited traits are autosomal, and that you do not
use sex chromosome symbols (i.e. X, Y) when performing these crosses. Be able to
apply probability calculations using a factorial equation for the results of these crosses,
and when doing, account for the probability of obtaining male or female progeny (i.e. ½).
73. As you do for sex-influenced and sex-limited crosses, be able to apply probability
calculations using a factorial equation for the results of sex-linked crosses; however, you
will be using sex chromosome symbols in your crosses with the trait alleles designated as
superscripts on your sex chromosome symbol, which for this class will be an X
chromosome (ex. XAXa). In sex-linked crosses, because your chromosomal symbols will
already designate the sex of the individual, you don’t have to account for the probability
of obtaining male or female progeny (i.e. ½) as you do for sex-influenced and sex-limited
crosses.