Genetics Study Guide
Short Answer
1. In Mendel’s experiments, what proportion of the plants in the F2 generation had a trait that had been absent in
the F1 generation?
2. Factors that control traits are called
3. Scientists call an organism that has two different alleles for a trait a
4. What does the notation TT mean to geneticists?
5. What does the notation Tt mean to geneticists?
6. What is probability?
7. What is the probability of producing a tall pea plant from a genetic cross between two hybrid tall pea plants?
8. What does a Punnett square show?
9. If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig (bb), what is the
probability that an offspring will have black fur?
10. An organism’s physical appearance is its
11. A purebred chicken with white feathers is crossed with a purebred chicken that has black feathers. Each of
their offspring has both black and white feathers. Why does this happen?
12. What is a mutation?
13. Which term refers to physical characteristics that are studied in genetics?
14. The different forms of a gene are called
15. An organism that has two identical alleles for a trait is
16. A heterozygous organism has
17. Chromosomes are made up of
18. Which of these traits is controlled by a gene with multiple alleles?
19. What are multiple alleles?
20. What controls variations in skin color among humans?
21. Which combination of sex chromosomes results in a male human being?
22. Why are sex-linked traits more common in males than in females?
23. What is a pedigree?
24. Genetic disorders are caused by
25. Which genetic disorder causes the body to produce unusually thick mucus in the lungs and intestines?
26. What is a karyotype?
27. Both parents of a child have type A blood. What might their child’s blood type be?
28. Sex-linked genes are genes on
29. A carrier is a person who has
30. Hemophilia is caused by a(n)
31. Down syndrome most often occurs when
32. What genetic disorder results in abnormally shaped blood cells?
Use the diagram to answer each question.
33. Which trait—white flowers or purple flowers—is controlled by a dominant allele? Which is controlled by a
recessive allele? How do you know?
34. In which generation are the parents purebred? In which generation are they hybrids?
35. In the F1 generation, what is the genotype of the offspring? What is their phenotype?
36. In the F2 generation, what percent of the offspring have purple flowers? What is the genotype of the purpleflowered offspring?
37. Suppose one of the parents of the F2 generation had been ww instead of Ww. What percent of the offspring
would have purple flowers? What percent would have white flowers?
Use the diagram to answer each question.
38. What do the circles in the pedigree represent? What do the squares represent?
Genetics Study Guide
Answer Section
SHORT ANSWER
1. ANS:
one fourth
DIF: L2
2. ANS:
genes.
REF: p. C-78
OBJ: C.3.1.1
DIF: L1
3. ANS:
hybrid.
REF: p. C-79
OBJ: C.3.1.2
STO: L.7.11, L.7.11.2, L.7.8.1
DIF: L2
REF: p. C-80
4. ANS:
two dominant alleles
OBJ: C.3.1.2
STO: L.7.11, L.7.11.2, L.7.8.1
DIF: L1
REF: p. C-80
OBJ: C.3.1.2
5. ANS:
one dominant allele and one recessive allele
STO: L.7.11, L.7.11.2, L.7.8.1
DIF: L3
REF: p. C-80
OBJ: C.3.1.2
6. ANS:
a number that describes how likely it is that an event will occur
STO: L.7.11, L.7.11.2, L.7.8.1
DIF: L1
7. ANS:
three in four
OBJ: C.3.2.1
STO: L.7.11, L.7.11.2
DIF: L2
REF: p. C-86
OBJ: C.3.2.1
8. ANS:
all the possible outcomes of a genetic cross
STO: L.7.11, L.7.11.2
DIF: L2
9. ANS:
100 percent
REF: p. C-86
OBJ: C.3.2.1
STO: L.7.11, L.7.11.2
DIF: L2
10. ANS:
phenotype.
REF: p. C-87
OBJ: C.3.2.1
STO: L.7.11, L.7.11.2
REF: p. C-84
DIF: L1
REF: p. C-88
OBJ: C.3.2.2
11. ANS:
The alleles for feather color are neither dominant nor recessive.
STO: L.7.11, L.7.11.2
DIF: L2
REF: p. C-89
12. ANS:
any change in a gene or chromosome
OBJ: C.3.2.3
STO: L.7.11.2
DIF: L1
13. ANS:
traits
REF: p. C-102
OBJ: C.3.4.3
STO: L.7.10, L.7.6, L.7.8.1
DIF: L2
14. ANS:
alleles.
REF: p. C-76
OBJ: C.3.1.1
DIF: L1
15. ANS:
homozygous.
REF: p. C-79
OBJ: C.3.1.2
STO: L.7.11, L.7.11.2, L.7.8.1
DIF: L1
REF: p. C-88
16. ANS:
two different alleles for a trait.
OBJ: C.3.2.2
STO: L.7.11, L.7.11.2
DIF: L1
REF: p. C-88
17. ANS:
many genes joined together.
OBJ: C.3.2.2
STO: L.7.11, L.7.11.2
DIF: L3
18. ANS:
blood type
OBJ: C.3.3.3
STO: L.7.8.1
REF: p. C-96
DIF: L1
REF: p. C-112
OBJ: C.4.1.1
19. ANS:
three or more forms of a gene that code for a single trait
STO: L.7.11, L.7.11.2, L.7.8
DIF: L1
20. ANS:
many genes
REF: p. C-112
OBJ: C.4.1.1
STO: L.7.11, L.7.11.2, L.7.8
DIF: L1
21. ANS:
XY
REF: p. C-112
OBJ: C.4.1.1
STO: L.7.11, L.7.11.2, L.7.8
DIF: L2
REF: p. C-113
OBJ: C.4.1.2
STO: L.7.8
22. ANS:
A recessive allele on the X chromosome will always produce the trait in a male.
DIF: L2
REF: p. C-114
OBJ: C.4.1.2
STO: L.7.8
23. ANS:
a chart that tracks which members of a family have a particular trait
DIF: L1
REF: p. C-119
OBJ: C.4.2.2
STO: L.7.11.2
24. ANS:
DNA mutations or changes in chromosomes.
DIF: L2
25. ANS:
cystic fibrosis
REF: p. C-118
OBJ: C.4.2.1
STO: L.7.11.1
DIF: L1
REF: p. C-118
26. ANS:
a picture of the chromosomes in a cell
OBJ: C.4.2.1
STO: L.7.11.1
DIF: L1
27. ANS:
Type A or type O
REF: p. C-120
OBJ: C.4.2.3
STO: L.7.11.1
DIF: L3
REF: p. C-112
28. ANS:
the X and Y chromosomes.
OBJ: C.4.1.1
STO: L.7.11, L.7.11.2, L.7.8
DIF: L1
REF: p. C-114
OBJ: C.4.1.2
29. ANS:
one recessive and one dominant allele for a trait.
STO: L.7.8
DIF: L1
REF: p. C-115
30. ANS:
recessive allele on the X chromosome.
STO: L.7.8
OBJ: C.4.1.2
DIF: L1
REF: p. C-118
OBJ: C.4.2.1
31. ANS:
chromosomes fail to separate properly during meiosis.
STO: L.7.11.1
DIF: L1
32. ANS:
sickle-cell disease
STO: L.7.11.1
REF: p. C-118
OBJ: C.4.2.1
DIF: L2
REF: p. C-118
OBJ: C.4.2.1
STO: L.7.11.1
33. ANS:
White flowers are controlled by a dominant allele. Purple flowers are controlled by a recessive allele.
Dominant alleles are represented by capital letters, and recessive alleles are represented by the lowercase
versions of the same letters.
DIF: L2
REF: p. C-80
OBJ: C.3.1.2
STO: L.7.11, L.7.11.2, L.7.8.1
34. ANS:
The parents in the F1 generation are purebred. The parents in the F2 generation are hybrids.
DIF: L3
REF: p. C-77, p. C-80
STO: L.7.11, L.7.11.2, L.7.8.1
35. ANS:
The genotype is Ww. The phenotype is white flowers.
OBJ: C.3.1.2
DIF: L2
REF: p. C-88
OBJ: C.3.2.2
STO: L.7.11, L.7.11.2
36. ANS:
In the F2 generation, 25% of the offspring have purple flowers. Their genotype is ww.
DIF: L3
REF: p. C-87
OBJ: C.3.2.1
STO: L.7.11, L.7.11.2
37. ANS:
If one of the parents had been ww, 50% of the offspring would have purple flowers and 50% would have
white flowers.
DIF: L3
REF: p. C-87
OBJ: C.3.2.1
38. ANS:
The circles represent females. The squares represent males.
STO: L.7.11, L.7.11.2
DIF: L1
REF: p. C-119
39. ANS:
F and J have the trait.
OBJ: C.4.2.2
STO: L.7.11.2
DIF: L1
REF: p. C-119
40. ANS:
A, C, N, and O are carriers of the trait.
OBJ: C.4.2.2
STO: L.7.11.2
OBJ: C.4.2.2
STO: L.7.11.2
DIF: L2
REF: p. C-119