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Genetics Study Guide
1. Relate “DNA” to “gene.”
2. Label the diagram below with the following terms: DNA, cell, nucleotides, gene, chromosome, nucleus.
3. Differentiate between a gene and a DNA molecule in terms of the number of proteins they code for.
4. Explain how parents pass genes to their offspring.
5. Describe what happens to gametes during fertilization.
6. Explain why living things always have TWO genes for every trait.
7. Relate “allele” to “gene.”
8. Identify “hair texture” as a gene or an allele, and defend your answer.
9. List two possible alleles for hair texture in humans.
10. Explain where new alleles come from.
11. Explain how it is possible for so many different alleles (versions of a gene) to exist.
12. Explain why the offspring of a brown-haired man and blonde woman would be considered a hybrid.
13. Complete the table below showing the alleles for different genes in pea plants.
Gene
Allele #1
Allele #2
Plant height
Seed shape
Seed color
14. Explain why the offspring of a tall pea plant and a short pea plant would be considered a hybrid.
15. Explain how plants are different from humans in terms of the gametes they produce.
16. Explain what “pollen” is.
17. Label the male parts and female part in the flower diagram below.
18. State Mendel’s hypothesis about hybrid pea plants.
19. Explain how Mendel prevented his pea plants from self-pollinating.
20. The diagram below shows the first part of Mendel’s experiment. Label the parent (P) generation and
the F1 generation. Also label the hybrid plants.
X
21. Based on the results of the experiment, explain why Mendel’s hypothesis was not supported.
22. From this experiment, state what Mendel concluded about alleles.
23. Explain why all of the F1 offspring were tall, even though they had one short parent.
24. Complete the diagram below showing how alleles were passed from the P generation to the F1
generation.
25. Describe what happens to alleles during segregation.
26. Describe what happens to alleles during fertilization.
27. The diagram below shows the second part of Mendel’s experiment Label the F1 generation and the F2
generation.
X
28. Describe the results of the F1 cross shown above.
29. Complete the diagram below showing how alleles were passed from the F1 generation to the F2
generation.
30. Explain why tt is the only possible allele combination for a short plant.
31. Explain why two recessive alleles were able to pair up during fertilization to produce a tt (short) plant.
32. Differentiate between segregation and fertilization in terms of what they do to alleles.
Genetics Problem #1: Baby Blue Eyes
The allele for brown eyes is dominant (B), while the allele for blue eyes is recessive (b).
a. What is the only possible allele combination for a blue-eyed person?
b. What are two possible allele combination for a brown-eyed person?
33. A blue-eyed baby is born to two brown-eyed parents. Complete the diagram below to show how this
type of inheritance is possible.
34. Explain why the parents in this diagram have brown eyes, even though they both carry the allele for
blue eyes.
35. Explain why bb is the only possible allele combination for a blue-eyed person.
36. Explain why two recessive alleles were able to pair up during fertilization to produce a blue-eyed baby.
37. The blue-eyed baby has a brown-eyed sister from the same parents. Explain how this is possible.
Genetics Problem #2: Black and White Twins
The allele for dark skin is dominant (D), while the allele for light skin is recessive (d).
a. What is the only possible allele combination for a light-skinned person?
b. What are two possible allele combination for a dark-skinned person?
38. A white woman and a black man have twins. One of the twins in black, while the other is white. Explain
how this type of inheritance is possible.
39. Explain why the father in this diagram has dark skin, even though he carries the allele for light skin.
40. Explain why dd is the only possible allele combination for the mother.
41. Explain why two recessive alleles were able to pair up during fertilization to produce a light-skinned
baby.
42. Explain why one of the sisters has dark skin.
Genetics Problem #3: Black Parents, White Baby
43. A light-skinned baby is born to two dark-skinned parents. Create a Punnett square to show how this
type of inheritance is possible.
Probabilities;
DD:
Dd:
dd:
Dark:
Light:
44. Describe how Punnett squares are used by geneticists.
45. If this couple decides to have another baby, what is the probability that the baby will have light skin?
46. If this couple decides to have another baby, what is the probability that the baby will have dark skin?
47. If this couple decides to have another baby, what is the probability that the baby will be a carrier?
48. Construct a Punnett square showing the P generation cross in Mendel’s experiment.
Probabilities;
TT:
Tt:
tt:
Tall:
Short:
49. Construct a Punnett square showing a cross between a Tt pea plant and a tt pea plant.
Probabilities;
TT:
Tt:
tt:
Tall:
Short:
50. Explain why the outer boxes in a Punnett square only have one allele in them.
51. Differentiate between the terms “genotype” and “phenotype.”
52. State whether “brown eyes” is a genotype or a phenotype.
53. Identify the genotype of a blue-eyed person.
54. Explain how two people can have the same phenotype for eye color, but different genotypes.
55. Differentiate between the terms “homozygous” and “heterozygous.”
56. State whether a blue-eyed person is homozygous or heterozygous, and defend your answer.
57. The allele for brown eyes (B) is dominant over the allele for blue eyes (b).
a. Identify the genotype of a homozygous dominant person:
b. Identify the genotype of a homozygous recessive person:
c. Identify the genotype of a heterozygous person:
d. Identify the phenotype of a homozygous dominant person:
e. Identify the phenotype of a homozygous recessive person:
f.
Identify the phenotype of a heterozygous person:
58. The allele for curly hair (H) is dominant over the allele for straight hair (h).
a. Identify the genotype of a homozygous dominant person:
b. Identify the genotype of a homozygous recessive person:
c. Identify the genotype of a heterozygous person:
d. Identify the phenotype of a homozygous dominant person:
e. Identify the phenotype of a homozygous recessive person:
f.
Identify the phenotype of a heterozygous person:
g. Construct a Punnett square showing a cross between a woman who is heterozygous and a man who is
homozygous recessive.
Probabilities;
HH:
Hh:
hh:
Curly:
Straight:
59. Explain how two-factor crosses are different from regular Punnett squares.
60. List the possible genotypes for:
a.
b.
c.
d.
Round yellow seed:
Wrinkled yellow seed:
Round green seed:
Wrinkled green seed:
61. Identify the color/shape phenotype for:
a. Homozygous recessive seed:
b. Heterozygous seed:
c. Homozygous dominant seed:
62. List all of the possible gametes that could be produced by a RrYy plant.
63. List all of the possible gametes that could be produced by a homozygous dominant plant.
64. Complete the two-factor cross for the P generation (a homozygous dominant seed and a homozygous recessive
seed).
65. Complete the two-factor cross for the F1 generation (two heterozygous hybrid seeds).
66. Explain why roundness and yellowness do not always stay together in a two-factor cross.
67. Explain why independent assortment is helpful to organisms.
68. Describe incomplete dominance.
69. Give an example of incomplete dominance.
70. Describe co-dominance.
71. Give an example of co-dominance.
72. A black cat and a white cat produce offspring with black and white spots. Identify this as codominance or
incomplete dominance, and defend your answer.
73. Identify wavy hair as incomplete dominance or co-dominance, and defend your answer.
74. Describe heterochromia, and identify it as a form of co-dominance or incomplete dominance.
75. Describe multiple-allele traits.
76. Give an example of a multiple-allele trait.
77. Describe polygenic traits.
78. Give an example of a polygenic trait.
79. “Blood type” is a classification of blood based on the presence or absence of certain proteins. There are 4
different blood types: A, B, AB, and O. Identify blood type as a multiple-allele trait or a polygenic trait, and
defend you answer.
80. Humans have a wide range of eye colors, from nearly black to pale blue. Identify human eye color as a multipleallele trait or a polygenic trait, and defend your answer.