AP Biology Genetics Unit Test Review
Basic Genetics Problems
1. What combination of alleles will show up in the gametes of an individual with the genotype
a. RrJj
b. RRjj
c. RrJJ
2. Genes S and T are not linked. If there is a 50% probability that allele S is in a gamete and
there is a 50% probability that allele T is in a gamete, what is the probability that both are in the
same gamete?
3. The trait for tall pea plants is (T) and the trait for short pea plants is (t). The trait for smooth
peas is (S) and the trait for wrinkled is (s). Two plants are crossed yielding an F1 generation with
612 tall plants with smooth peas and 188 short plants with wrinkled peas. Which of the following is
the most likely genotype of the parent generation?
(A) ttss x ttss
(B) TTss x TTss
(C) TtSs x TtSs
(D) TTSS x ttss
(E) TtSS x Ttss
4. A male and female have 3 offspring all of which are female. The couple is now pregnant again.
What is the likelihood that the next child will be a female?
(A) 1/16
(B) ¼
(C) 1/3
(D) ½
(E) ¾
5. What is the likelihood that a couple will have 4 offspring all of which are female?
(A) 1/16
(B) ¼
(C) 1/3
(D) ½
(E) ¾
6. What is the probability that each of the following pairs of parents will produce the indicated
offspring (assume independent assortment of all gene pairs)?
a. AABBCC x aabbcc Æ AaBbCc
b. AABbCc x AaBbCc Æ AAbbCC
c. AaBbCc x AaBbCc Æ AaBbCc
7. A child is born with the blood type B. The mother of the child is blood type O. Which of the
following statements is most correct?
(A) The father must be type B
(B) The father could be type AB
(C) The father passed along a recessive allele
(D) The mother could have passed along a type B allele
(E) The mother could have passed along a dominant allele
8. If traits X, Y, and Z are consistently inherited together, which of the following best explains why
this is the case?
(A) These 3 traits are all dominant.
(B) The parents both carry the dominant form of each trait.
(C) These 3 traits are located on different chromosomes
(D) These 3 traits are located close to each other on the same chromosome.
(E) These 3 traits are located far from each other on the same chromosome.
9. Hemophilia is a sex-linked recessive trait. A male hemophiliac and phenotypically normal
female have a girl that is a hemophiliac. All of the following statements are correct EXCEPT:
(A) The daughter inherited a recessive gene from each parent.
(B) The daughter inherited a dominant allele from her mother.
(C) The mother is a carrier of hemophilia
(D) The genotype of the mother is XHXh
(E) The genotype of the father is XhY
10. The weight of the fruit in a certain variety of squash is determined by allelic pairs of two loci
on a chromosome. AABB produced fruits that average 2kg each and aabb produces fruits that are
1 kg each. Each allele represented by a capital letter addes 0.25 kg. When a plant that produces
2 kg fruits is crossed with a plant that produces 1 kg fruits, and the offspring produce fruits that
are 1.5 kg each. What would be the weights of the fruits produced by the F2 plants if these F1
plants are crossed?
Chi Square
11. A white flower was crossed with a red flower. The following offspring results were obtained.
225 white flowers
525 pink flowers
240 red flowers
Write a hypothesis predicting the mode of inheritance for the flower color trait. Reject or accept
you hypothesis with a chi square.
Gene Mapping
12. Observe the collected recombination data below. Recent experiments show that gene C is more
closely linked with D than with A. Reconstruct a gene map and determine the map distance
between C and D.
GENE CROSSOVER
FREQUENCY
A-B 7%
A-C 18%
C-D ?
B-D 35%
13. A cross was made between two strains of the hypothetical plant Blue Lagmaratus, a
man eating species. Oblivious to the hazards involved in working with this plant, a
dedicated and nimble researcher made the following cross: a heterozygous wild type
plant was crossed to a homozygous recessive, quick tentacled (q), accelerated appetite
(a), attractively scented (s) plant. The following progeny were obtained.
435 quick tentacles, accelerated appetite, obnoxious scent
22 quick, normal, obnoxious
28 slow, normal, obnoxious
450 slow, normal, attractive
7 quick, normal, attractive
23 quick, accelerated, attractive
27 slow, accelerated, attractive
8 slow, accelerated, obnoxious
Determine the gene order and map distances.
14. Individuals of genotypes AaBb were mated to individuals of genotype aabb. One thousand
offspring were counted with the following results:
474 Aabb, 480 aaBb, 20 AaBb, 26 aabb
What is the general term for this type of genetic cross (when a parent is mated with another that
has all recessive traits?
Are these genes linked?
If these genes are linked, identify the parental phenotypes and the recombinant phenotypes.
If these genes are linked, how many map units apart are they?
Identify Mendel’s Law that would be occurring if the genes are not linked.
Nonnuclear Inheritance Problems
15. When looking at a pedigree of a genetic disease, what characteristics would you expect to find
in the pedigree if the disease was a non-nuclear inherited disease?
Genetic Diseases
16. Give examples of diseases that are the result of a single gene disorder.
17. What is nondisjunction? Give examples of diseases that are the result of nondisjunction.
18. Give examples of diseases that are the result of chromosomal errors.
19. Why are chromosomal mutations of autosomes usually more harmful than chromosomal
mutations of sex chromosomes?
18. Explain the relationship between an organism’s environment, its genome, and its phenotype.
Cite specific examples.