Genetics: From Genes to Genomes 8th Edition Hartwell – Test
Bank( 200 Multiple-Choice Practice Questions with Answers
and Explanations)
1. Which of the following statements is true concerning modern‐day farming and agriculture? (Choose
ALL that apply.)
A) Triploid plants are seedless due to errors that occur in mitosis.
B) Triploid GMO fish pose a greater risk than diploid GMO fish if released in the wild because they
contain 50% more genomic information that can be introduced into the wild population.
C) All man-made seedless watermelons are GMOs.
D) Polyploidy in plants is induced by treating plant cells with drugs that disrupt mitosis.
E) Polyploid plants tend to have larger and more robust fruit.
Correct Answer: D and E
Rationale: Polyploidy in plants can be induced with drugs such as colchicine that disrupt mitosis. Many
polyploid plants exhibit larger fruits and increased vigor (mutations that are often commercially
valuable). Triploid plants (e.g., seedless watermelon) are not necessarily GMOs; they are usually
produced by crossing diploid and tetraploid parents. Option A is incorrect because triploid seedlessness
is due to problems in meiosis, not mitosis.
2. A man is found to have two X chromosomes and no Y chromosomes. DNA testing reveals that he has a
functional copy of the SRY gene. How could this situation have arisen? (Choose ALL that apply.)
A) A tandem duplication of a segment of the Y chromosome in his father or another ancestor.
B) An inversion of a segment on one of his X chromosomes in his father or another ancestor.
C) A translocation of a segment of the Y chromosome in his father.
D) A deletion of a large segment of one of his X chromosomes in his father.
,Correct Answer: C
Rationale: A translocation of the SRY-bearing segment of the Y chromosome to an X chromosome in the
father’s germline could result in an XX male with normal SRY function. A deletion on the X (D) would not
introduce SRY. Duplications (A) or inversions (B) of Y‑specific segments onto the X are not the typical
mechanism.
3. 20% – 40% of women with Turner syndrome have an X chromosome derived from their father. Which
of the following are potential causes? (Choose ALL that apply.)
A) A non‑disjunction error in maternal meiosis I.
B) A non‑disjunction error in maternal meiosis II.
C) Non‑disjunction errors in both parents.
D) A non‑disjunction error in paternal meiosis I.
E) A non‑disjunction error in paternal meiosis II.
F) The location of the error can’t be determined.
Correct Answer: A and B
Rationale: When the single X in Turner syndrome comes from the father, the error must be in the
mother, causing loss of her X. Non‑disjunction in maternal meiosis I or II can generate an egg with no X
chromosome, which when fertilized by a normal X‑bearing sperm produces an XO female. The other
options are incorrect for this scenario.
4. Why are trisomies for chromosomes 13 and 18 sometimes viable, even though trisomies for
chromosomes 14, 15, 16, 17, 19, 20 and 22 are not? (Choose ALL that apply.)
A) Chromosomes 13 and 18 are shorter than the other chromosomes mentioned.
B) The genes on chromosomes 13 and 18 are not as sensitive to gene dosage as those on the other
chromosomes.
C) There are fewer genes on chromosomes 13 and 18 than on the other chromosomes.
,D) The genes on chromosomes 13 and 18 are all haplo‑sufficient but those on the other chromosomes
are not.
E) Functional copies of genes on chromosomes 13 and 18 are not necessary for development.
Correct Answer: C
Rationale: Chromosomes 13 and 18 are relatively gene‑poor (e.g., chromosome 18 has about 300 genes,
whereas chromosome 14 or 15 have many more critical genes). Having fewer genes makes an extra copy
less likely to be lethal. Note that viability is still greatly reduced (Patau and Edwards syndromes), but live
birth can occur
5. Why do reciprocal translocations often cause infertility? (Choose ALL that apply.)
A) Loss of genes.
B) Meiotic errors.
C) Non‑allelic homologous recombination.
D) Reduction of replication origins.
E) Gene‑dosage imbalance.
Correct Answer: B
Rationale: Reciprocal translocations create problems during meiosis because the derivative
chromosomes form quadrivalent pairing structures, leading to unbalanced gametes after segregation.
The primary defect is meiotic disturbance, not direct loss of genes or altered gene dosage.
6. The concept of synteny refers to:
A) The presence of the same genes on the same chromosome in different species.
B) The linear order of genes on a single chromosome.
C) The phenomenon of two genes being inherited together more often than expected.
D) The arrangement of nucleotide sequences that are conserved across species.
, Correct Answer: A
Rationale: Synteny describes the situation where two or more genes are located on the same
chromosome, especially across different species, indicating a conserved block of chromosomal material.
Option B refers to gene order, option C describes linkage, and option D is about sequence conservation.
7. What is a possible consequence of a chromosome inversion in a heterozygote?
A) Permanent loss of all genes within the inverted region.
B) Formation of inversion loops during meiosis I, resulting in unbalanced gametes.
C) Complete sterility of all offspring.
D) Immediate change of the phenotype due to gene disruption.
Correct Answer: B
Rationale: In inversion heterozygotes, homologous chromosomes form inversion loops to allow pairing.
Recombination within the loop produces dicentric and acentric chromosomes, leading to unbalanced
gametes and reduced fertility. There is no loss of genetic information in the inversion carrier’s somatic
cells.
8. A woman with a balanced reciprocal translocation (46,XX,t(2;5)(q21;q31)) is trying to conceive. The
main factor affecting her risk of having a child with a partial trisomy or monosomy is:
A) The overall size of the translocated segments.
B) Whether the breakpoints are close to the centromere.
C) The specific genes located at the breakpoints.
D) The segregation pattern during meiosis.
Bank( 200 Multiple-Choice Practice Questions with Answers
and Explanations)
1. Which of the following statements is true concerning modern‐day farming and agriculture? (Choose
ALL that apply.)
A) Triploid plants are seedless due to errors that occur in mitosis.
B) Triploid GMO fish pose a greater risk than diploid GMO fish if released in the wild because they
contain 50% more genomic information that can be introduced into the wild population.
C) All man-made seedless watermelons are GMOs.
D) Polyploidy in plants is induced by treating plant cells with drugs that disrupt mitosis.
E) Polyploid plants tend to have larger and more robust fruit.
Correct Answer: D and E
Rationale: Polyploidy in plants can be induced with drugs such as colchicine that disrupt mitosis. Many
polyploid plants exhibit larger fruits and increased vigor (mutations that are often commercially
valuable). Triploid plants (e.g., seedless watermelon) are not necessarily GMOs; they are usually
produced by crossing diploid and tetraploid parents. Option A is incorrect because triploid seedlessness
is due to problems in meiosis, not mitosis.
2. A man is found to have two X chromosomes and no Y chromosomes. DNA testing reveals that he has a
functional copy of the SRY gene. How could this situation have arisen? (Choose ALL that apply.)
A) A tandem duplication of a segment of the Y chromosome in his father or another ancestor.
B) An inversion of a segment on one of his X chromosomes in his father or another ancestor.
C) A translocation of a segment of the Y chromosome in his father.
D) A deletion of a large segment of one of his X chromosomes in his father.
,Correct Answer: C
Rationale: A translocation of the SRY-bearing segment of the Y chromosome to an X chromosome in the
father’s germline could result in an XX male with normal SRY function. A deletion on the X (D) would not
introduce SRY. Duplications (A) or inversions (B) of Y‑specific segments onto the X are not the typical
mechanism.
3. 20% – 40% of women with Turner syndrome have an X chromosome derived from their father. Which
of the following are potential causes? (Choose ALL that apply.)
A) A non‑disjunction error in maternal meiosis I.
B) A non‑disjunction error in maternal meiosis II.
C) Non‑disjunction errors in both parents.
D) A non‑disjunction error in paternal meiosis I.
E) A non‑disjunction error in paternal meiosis II.
F) The location of the error can’t be determined.
Correct Answer: A and B
Rationale: When the single X in Turner syndrome comes from the father, the error must be in the
mother, causing loss of her X. Non‑disjunction in maternal meiosis I or II can generate an egg with no X
chromosome, which when fertilized by a normal X‑bearing sperm produces an XO female. The other
options are incorrect for this scenario.
4. Why are trisomies for chromosomes 13 and 18 sometimes viable, even though trisomies for
chromosomes 14, 15, 16, 17, 19, 20 and 22 are not? (Choose ALL that apply.)
A) Chromosomes 13 and 18 are shorter than the other chromosomes mentioned.
B) The genes on chromosomes 13 and 18 are not as sensitive to gene dosage as those on the other
chromosomes.
C) There are fewer genes on chromosomes 13 and 18 than on the other chromosomes.
,D) The genes on chromosomes 13 and 18 are all haplo‑sufficient but those on the other chromosomes
are not.
E) Functional copies of genes on chromosomes 13 and 18 are not necessary for development.
Correct Answer: C
Rationale: Chromosomes 13 and 18 are relatively gene‑poor (e.g., chromosome 18 has about 300 genes,
whereas chromosome 14 or 15 have many more critical genes). Having fewer genes makes an extra copy
less likely to be lethal. Note that viability is still greatly reduced (Patau and Edwards syndromes), but live
birth can occur
5. Why do reciprocal translocations often cause infertility? (Choose ALL that apply.)
A) Loss of genes.
B) Meiotic errors.
C) Non‑allelic homologous recombination.
D) Reduction of replication origins.
E) Gene‑dosage imbalance.
Correct Answer: B
Rationale: Reciprocal translocations create problems during meiosis because the derivative
chromosomes form quadrivalent pairing structures, leading to unbalanced gametes after segregation.
The primary defect is meiotic disturbance, not direct loss of genes or altered gene dosage.
6. The concept of synteny refers to:
A) The presence of the same genes on the same chromosome in different species.
B) The linear order of genes on a single chromosome.
C) The phenomenon of two genes being inherited together more often than expected.
D) The arrangement of nucleotide sequences that are conserved across species.
, Correct Answer: A
Rationale: Synteny describes the situation where two or more genes are located on the same
chromosome, especially across different species, indicating a conserved block of chromosomal material.
Option B refers to gene order, option C describes linkage, and option D is about sequence conservation.
7. What is a possible consequence of a chromosome inversion in a heterozygote?
A) Permanent loss of all genes within the inverted region.
B) Formation of inversion loops during meiosis I, resulting in unbalanced gametes.
C) Complete sterility of all offspring.
D) Immediate change of the phenotype due to gene disruption.
Correct Answer: B
Rationale: In inversion heterozygotes, homologous chromosomes form inversion loops to allow pairing.
Recombination within the loop produces dicentric and acentric chromosomes, leading to unbalanced
gametes and reduced fertility. There is no loss of genetic information in the inversion carrier’s somatic
cells.
8. A woman with a balanced reciprocal translocation (46,XX,t(2;5)(q21;q31)) is trying to conceive. The
main factor affecting her risk of having a child with a partial trisomy or monosomy is:
A) The overall size of the translocated segments.
B) Whether the breakpoints are close to the centromere.
C) The specific genes located at the breakpoints.
D) The segregation pattern during meiosis.
