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BIO207: Introductory Genetics | 100-Question Master Prep
University of Toronto (UofT) Edition
Module 1: Mendelian Principles & Probability
1. A cross between two true-breeding plants (One Purple, One White) results in all Purple
F1 offspring. What is the expected ratio of Purple to White in the F2 generation?
A) 1:1
B) 3:1
C) 9:3:3:1
D) 1:2:1
Elaboration: This is a classic Mendelian monohybrid cross. The F1 are all heterozygotes,
and their self-cross produces a 3:1 phenotypic ratio in the F2.
2. Which statistical test is used in BIO207 labs to determine if observed genetic data fits an
expected Mendelian ratio?
A) T-test
B) Chi-Square ($\chi^2$) Test
C) ANOVA
D) Linear Regression
Elaboration: The Chi-Square test evaluates the "Goodness of Fit" between observed
offspring counts and the theoretical expectations.
3. In a testcross, a dominant phenotype individual of unknown genotype is crossed with:
A) A homozygous dominant individual.
B) A heterozygote.
C) A homozygous recessive individual.
D) A hemizygote.
Elaboration: Because the tester is homozygous recessive, the phenotypes of the offspring
directly reveal the alleles of the unknown parent.
4. If two genes show a 9:7 phenotypic ratio in the F2, what does this suggest?
A) Incomplete dominance.
B) Duplicate recessive epistasis (Complementary gene action).
C) Linked genes.
, D) Lethal alleles.
Elaboration: A 9:7 ratio indicates that a functional product from both genes is required to
produce the dominant phenotype.
5. What is the probability of a couple having three girls in a row?
A) 1/2
B) 1/4
C) 1/8
D) 1/16
Elaboration: Using the Product Rule for independent events: $1/2 \times 1/2 \times 1/2 =
1/8$.
6. "Pleiotropy" occurs when:
A) Many genes affect one trait.
B) One gene affects multiple, distinct phenotypic traits.
C) A gene is masked by another.
D) The environment changes the gene.
Elaboration: An example is Marfan syndrome, where one gene mutation affects the heart,
eyes, and skeletal system.
7. A woman with Type A blood (whose father was Type O) has a child with a man with
Type B blood (whose mother was Type O). What is the chance the child is Type O?
A) 0%
B) 25%
C) 50%
D) 100%
Elaboration: Both parents are carriers of the 'i' allele ($I^A i$ and $I^B i$). The cross
results in a 1/4 chance for the 'ii' (Type O) genotype.
8. If a trait is "autosomal dominant," an affected child must have:
A) Two affected parents.
B) At least one affected parent.
C) No affected parents (skips generations).
D) Only an affected mother.
Elaboration: Dominant traits do not skip generations; the allele must be passed directly
from a parent to the offspring.
, 9. In a pedigree, a horizontal line between a circle and a square represents:
A) Siblings.
B) Mating/Consanguinity.
C) Deceased individuals.
D) Twins.
Elaboration: Circles represent females and squares represent males; the horizontal line
indicates a cross.
10. The sum of all probabilities for all possible outcomes in a genetic cross must equal:
A) 0.5
B) 1.0
C) 100
D) The number of offspring.
Elaboration: Probability theory dictates that the total sample space must sum to 1.
Module 2: Chromosomes & Sex Linkage
11. How many autosomes are found in a normal human somatic cell?
A) 46
B) 23
C) 44
D) 22
Elaboration: Humans have 46 total chromosomes: 44 autosomes and 2 sex chromosomes
(XX or XY).
12. A "homologous pair" of chromosomes consists of:
A) Two identical sister chromatids.
B) One maternal and one paternal chromosome carrying the same genes.
C) X and Y chromosomes.
D) Chromosomes that do not pair in meiosis.
Elaboration: Homologs are similar in size and gene content but may carry different
alleles.
13. At which stage of meiosis do sister chromatids finally separate?
A) Anaphase I
B) Anaphase II
C) Metaphase I
BIO207: Introductory Genetics | 100-Question Master Prep
University of Toronto (UofT) Edition
Module 1: Mendelian Principles & Probability
1. A cross between two true-breeding plants (One Purple, One White) results in all Purple
F1 offspring. What is the expected ratio of Purple to White in the F2 generation?
A) 1:1
B) 3:1
C) 9:3:3:1
D) 1:2:1
Elaboration: This is a classic Mendelian monohybrid cross. The F1 are all heterozygotes,
and their self-cross produces a 3:1 phenotypic ratio in the F2.
2. Which statistical test is used in BIO207 labs to determine if observed genetic data fits an
expected Mendelian ratio?
A) T-test
B) Chi-Square ($\chi^2$) Test
C) ANOVA
D) Linear Regression
Elaboration: The Chi-Square test evaluates the "Goodness of Fit" between observed
offspring counts and the theoretical expectations.
3. In a testcross, a dominant phenotype individual of unknown genotype is crossed with:
A) A homozygous dominant individual.
B) A heterozygote.
C) A homozygous recessive individual.
D) A hemizygote.
Elaboration: Because the tester is homozygous recessive, the phenotypes of the offspring
directly reveal the alleles of the unknown parent.
4. If two genes show a 9:7 phenotypic ratio in the F2, what does this suggest?
A) Incomplete dominance.
B) Duplicate recessive epistasis (Complementary gene action).
C) Linked genes.
, D) Lethal alleles.
Elaboration: A 9:7 ratio indicates that a functional product from both genes is required to
produce the dominant phenotype.
5. What is the probability of a couple having three girls in a row?
A) 1/2
B) 1/4
C) 1/8
D) 1/16
Elaboration: Using the Product Rule for independent events: $1/2 \times 1/2 \times 1/2 =
1/8$.
6. "Pleiotropy" occurs when:
A) Many genes affect one trait.
B) One gene affects multiple, distinct phenotypic traits.
C) A gene is masked by another.
D) The environment changes the gene.
Elaboration: An example is Marfan syndrome, where one gene mutation affects the heart,
eyes, and skeletal system.
7. A woman with Type A blood (whose father was Type O) has a child with a man with
Type B blood (whose mother was Type O). What is the chance the child is Type O?
A) 0%
B) 25%
C) 50%
D) 100%
Elaboration: Both parents are carriers of the 'i' allele ($I^A i$ and $I^B i$). The cross
results in a 1/4 chance for the 'ii' (Type O) genotype.
8. If a trait is "autosomal dominant," an affected child must have:
A) Two affected parents.
B) At least one affected parent.
C) No affected parents (skips generations).
D) Only an affected mother.
Elaboration: Dominant traits do not skip generations; the allele must be passed directly
from a parent to the offspring.
, 9. In a pedigree, a horizontal line between a circle and a square represents:
A) Siblings.
B) Mating/Consanguinity.
C) Deceased individuals.
D) Twins.
Elaboration: Circles represent females and squares represent males; the horizontal line
indicates a cross.
10. The sum of all probabilities for all possible outcomes in a genetic cross must equal:
A) 0.5
B) 1.0
C) 100
D) The number of offspring.
Elaboration: Probability theory dictates that the total sample space must sum to 1.
Module 2: Chromosomes & Sex Linkage
11. How many autosomes are found in a normal human somatic cell?
A) 46
B) 23
C) 44
D) 22
Elaboration: Humans have 46 total chromosomes: 44 autosomes and 2 sex chromosomes
(XX or XY).
12. A "homologous pair" of chromosomes consists of:
A) Two identical sister chromatids.
B) One maternal and one paternal chromosome carrying the same genes.
C) X and Y chromosomes.
D) Chromosomes that do not pair in meiosis.
Elaboration: Homologs are similar in size and gene content but may carry different
alleles.
13. At which stage of meiosis do sister chromatids finally separate?
A) Anaphase I
B) Anaphase II
C) Metaphase I
