Biology 160
NAME: _______________________________________
Reading Guide 12: Population Dynamics, Humans, Part II
This is DUE: _________________
Come prepared to share your findings with your group.
*As before, please turn in only the Critical Thinking questions on a separate sheet of paper.
Critical Thinking questions: 6, 9, 18, 23, 24, 25, 26, 28, 43, 61, 65, 78, 94, 98
What you’ll learn in this reading guide:
 How genes are inherited in both simple and more complex patterns and apply it to malaria resistance
 How genotype (our sequence of DNA nucleotides) affects phenotype (what we look like) and apply it to
malaria resistance
 How genetic variation in a population (its gene pool) can change over time and apply it to malaria
resistance
** Fill this reading guide out as you are reading the chapters. This will help you to pull out the important
information that will help us to understand how natural selection occurs.
Readings:  Essential Biology, 4th or 5th Ed. (Simon, Reece, & Dickey)
Ch 9, pg. 144-167 (Patterns of Inheritance)
Ch 13, pg. 258-265 (Analyzing Gene Pools and the Mechanisms of Evolution)
While reading these chapters, constantly ask yourself, “How is this information helping me to understand
how human resistance to malaria happens?”
Chapter 9, pg 144-167
1. Make sure you read the Dog Breeding information on pg 145.
2. Who was Gregor Mendel, what did he study, and what was his scientific background?
3. What scientific argument did he make in his 1866 paper?
4. What are these “heritable factors” called today?
5. What are the characteristics of pea plants that allowed Mendel to perform his genetic experiments?
6. Critical Thinking:
a) You have one pea plant that you would like to mate with itself. What is this process called?
b) You have two different plants that you would like to mate together. What is this process called?
c) You have a family of pea plants that have the same characteristics and always produce the same
characteristics when you mate them together. What is this variety of pea plant called?
7. What is a “hybrid”?
8. What is a “genetic cross”?
9. Critical Thinking: If you allowed a true-breeding plant to self-fertilize, would this be considered a genetic
cross? Why?
10.
a) A dog breeder has a male (true-breeding) purebred dog of one breed and a female (true-breeding)
purebred dog of another breed he would like to mate together. In genetic terms, what is this generation
called?
b) In genetic terms what is their offspring’s generation called?
c) A brother and sister of the generation in b) were then mated together. What is their offspring’s
generation called?
11. What is a monohybrid cross?
12. What is an allele?
13. What does it mean to be homozygous?
14. What does it mean to be heterozygous?
15. What is a dominant allele? How is represented?
16. What is a recessive allele? How is it represented?
17. Explain what Mendel’s law of segregation means?
18. Critical Thinking: Yea Math!!! How do you express a 3:1 ratio in fractions? (Need a hint? Look at the F2
generation in Figure 9.5)
19. It is important that you be able to understand how to think about inheritance by using symbols. This can be
very difficult. Please copy the information from Figure 9.6 here and make sure you understand how they
translated Mendel’s flower color experiment to the symbols P and p.
20. What is a Punnett square?
21. What is the difference between phenotype and genotype?
22. Redraw Figure 9.7 here, making sure you understand what homologous chromosomes, loci, and alleles are.
23. Critical Thinking:
a) Do the same genes need to be at the same location on homologous chromosomes? YES or NO
b) Do the same alleles need to be at the same location on homologous chromosomes? YES or NO
24. Critical Thinking: If the dominant allele for being able to wiggle your ears is E and the recessive allele for
not being able to wiggle your ears is e,
a) draw a diagram of two homologous chromosomes for an individual who is heterozygous for being
able to wiggle their ears.
b) How would you represent this person’s genotype using E and e?
c) What is this person’s phenotype?
25. Critical Thinking: At the time of Mendel’s studies, no one knew how traits were passed on from parents to
offspring, much less that chromosomes carried genes! In fact, the knowledge that meiosis split the number of
chromosomes in half was only worked out after Mendel published his paper. Now that we know about
chromosomes and meiosis, discuss how meiosis could explain Mendel’s law of segregation.
26. Critical Thinking: How can an allele be recessive? Well, simplifying the process of generating pea flower
color, we can say that there is a transcription factor that is required to express the enzymes that make the purple
pigment molecule in the flower cells. If the gene encoding this transcription factor is mutated in such a way
that the protein product is no longer functional, then a plant that carries this allele will not be able to express the
enzymes that synthesize the purple pigment, causing the flower to remain white. Write down any questions you
may have about this information.
Using this information, what is the phenotype and what type of transcription factor, functional and/or mutated,
would be produced in a plant with the genotype
a) PP?
b) pp?
c) Pp?
d) What correlation do you see between the type of enzyme expressed and the phenotype?
27. What is a dihybrid cross?
28. Critical Thinking: In Figure 9.8 (b)
a) what are the gametes produced by the F1 generation?
b) Use the process of meiosis to explain how these gametes were generated (For help, redraw Figure
8.16 and pretend that the R and r alleles are found on the large homologous chromosomes and the Y and
y alleles are found on the small homologous chromosomes).
29. What is the phenotypic ratio of the F2 generation in Figure 9.8 (b)?
30. What is the law of independent assortment?
31. Think Back: Refer to pg 135 and discuss how Mendel’s law of independent assortment can be explained by
the independent assortment of chromosomes in meiosis.
32. I want you to keep thinking that the alleles that we’ll be studying in this chapter actually code for a protein
product with a function in the organism. In Figure 9.9,
a) what does the protein product of the B allele for coat color do?
b) what does the protein product of the N allele for vision do?
c) Based on question 26 of this reading guide, what do you think may have happened to the b and n
alleles?
33. What is a testcross and why is it used?
34. Why is the probability that a tossed coin will come up heads equal to ½?
35. According to the text why is it significant that the probability of obtaining heads on every coin toss is equal
to ½?
36. What is the rule of multiplication?
37. What is a wild-type trait?
38. Are all wild-type traits dominant alleles?
39. Make sure you can answer the Checkpoint questions. If not, write your questions here:
40. Redraw the family pedigree in Figure 9.13 taking care to note what symbols are used for male and female,
how relationships in the family are drawn, and how phenotypes are noted.
41. What is a pedigree used for?
42. What is the definition of a carrier?
43. Critical Thinking: If the z allele is a recessive disorder allele, circle which of the following is a carrier:
ZZ Zz
zz
44. From Table 9.1 make note of 2 recessive disorders and 2 dominant disorders that interest you here:
a)
b)
c)
d)
45. For your information: The allele for cystic fibrosis carries a mutation in a membrane transport channel (it
transports chloride ions Cl-). This is a nonsense mutation that places a stop codon in the middle of the gene,
causing its protein product to be nonfunctional. Luckily, a person who has at least one functional allele of this
transport channel does not suffer from the disease.
46. Why might there be an uneven distribution of genetic disorders among ethnic groups?
47. Why is inbreeding more likely to produce offspring homozygous for a harmful recessive trait?
48. Why are lethal dominant alleles much less common than lethal recessive alleles?
49. Make sure you can answer the Checkpoint questions. If not, write your questions here:
50. Who are Mendel’s laws applicable to?
51. What can Mendel’s laws not explain?
52. Are the cases where Mendel’s laws can be applied relatively common or relatively rare?
53. What is incomplete dominance?
54. Redraw Figure 9.18 to understand the phenotypic and genotypic ratios seen in incomplete dominance.
55. How many LDL receptors are expressed in a person heterozygous for the hypercholesterolemia allele
relative to a homozygous normal individual?
56. Explain how you can have multiple alleles for a single gene?
57. What is codominance? Give an example.
58. How do you distinguish codominance from incomplete dominance?
59. What is pleiotropy?
60. What is sickle cell disease?
61. Critical Thinking:
a) What does it mean that the two alleles, one for sickle cell hemoglobin, one for normal hemoglobin,
are codominant?
b) Why is sickle cell disease pleiotropic?
62. What is polygenic inheritance? Give an example.
63. How does polygenic inheritance compare to pleiotropy?
64. What is the role of the environment in an organism’s characteristics?
65. Critical Thinking: What would the genotypes and phenotypes be of the possible offspring of two parents
who were both heterozygous for the sickle cell allele? Use a Punnett square to show this. For your allele
symbols, please use A to designate the normal hemoglobin allele and S to designate the sickle-cell hemoglobin
allele.
a) What is the genotype of the father? (Remember, this must be diploid)
b) What is the genotype of the mother? (Remember, this must be diploid)
c) What is the genotype of the gametes (sperm) produced by the father? (Remember, this must be
haploid)
d) What is the genotype of the gametes (eggs) produced by the mother? (Remember, this must be
haploid)
e) Place the haploid gamete genotypes in a Punnett Square and show the possible diploid genotypes of
their offspring.
f) What are the phenotypes of each of the possible genotypes?
 Normal, no malaria resistance:
 Normal with sickle cell trait, with malaria resistance
 Sickle cell disease
66. What is the chromosome theory of inheritance?
67. Redraw Figure 9.24 here to help you understand the chromosomal basis of inheritance and its relation to
meiosis.
68. What are linked genes?
69. Think Back: About how many genes are carried on a human chromosome?
70. How does crossing over help explain Morgan’s fruit fly experiment in Figure 9.25?
71. What is the recombination frequency?
72. What is a linkage map?
73. How is a linkage map constructed?
74. Make sure you can answer the Checkpoint questions. If not, write your questions here:
75.
a) What determines whether a human will be male?
b) will be female?
76. What is a sex-linked gene?
77. Redraw Figure 9.31 so that you understand the notation used to symbolized a sex-linked gene and how sexlinked genes affect the phenotypic ratios of the offspring.
78. Critical Thinking:
a) How many copies of an X-linked gene do females carry? Why?
b) How many copies of an X-linked gene do males carry? Why?
79. Why might a recessive phenotype show up more frequently in males than in females?
80. Describe the two sex-linked human disorders explained in the text:
a)
b)
81. Make sure that you can answer the Checkpoint questions. If not, write your questions here:
Chapter 13, pg 258-265
Now that we covered how alleles can be inherited in individuals, let’s take a look at how often an allele shows
up in a population (its allele frequency) can change over time. The processes that affect allele frequency in a
population are known together as microevolution.
82. What is a gene pool?
83. What does p + q = 1 mean? Give an example using two alleles.
84. What is the Hardy-Weinberg formula?
85. How was this equation derived?
86. What can you use the Hardy-Weinberg formula for?
87. How can you tell if a population is evolving?
88. What is microevolution?
89. Make sure that you can answer the Checkpoint questions. If not, write your questions here:
90. What is genetic drift?
91. Redraw Figure 13.22 to help you understand the effects of genetic drift.
92. Describe the two mechanisms of genetic drift and provide an example to help you remember it:
a)
b)
93. What is gene flow?
94. Critical Thinking: How can a new allele (a new mutation in an existing allele) increase its frequency in a
population?
95. What is the biological definition of fitness? Provide the example of the “toughest frog in the pond.”
96. Redraw Figure 13.28 to help you to understand the three general outcomes of natural selection. Make sure
you describe these three outcomes in words as well!
97. Make sure you can answer the Checkpoint questions. If not, write your questions here:
98. Critical Thinking: Summarize “The Evolution Connection” on page 265 in your own words. How did
human resistance to malaria come about? Incorporate the mechanisms of meiosis, genetic variation, patterns of
inheritance, and microevolution in your answer.