Question 1

Which of the following best describes the difference between aneuploidy and euploidy in human chromosomes?

Accepted Answer

Aneuploidy refers to a change in the number of individual chromosomes, while euploidy refers to a change in the number of entire sets of chromosomes.

Question 2

A karyotype analysis of a patient reveals 47 chromosomes, including two X chromosomes and one Y chromosome. Which syndrome does this individual most likely have?

Accepted Answer

Klinefelter syndrome

Question 3

Which of the following is the most common mechanism leading to Down syndrome (trisomy 21) in humans?

Accepted Answer

Meiotic nondisjunction during maternal meiosis I

Question 4

A plant species has a diploid number of 14 chromosomes. An individual is found with 21 chromosomes. What is the best description of this individual's chromosomal constitution?

Accepted Answer

Triploid

Question 5

Which of the following chromosomal rearrangements is most likely to result in a reduction in chromosome number in a human karyotype?

Accepted Answer

Robertsonian translocation

Question 6

A child is diagnosed with Prader-Willi syndrome. Genetic testing reveals two copies of chromosome 15, both inherited from the mother. What is the most likely genetic mechanism?

Accepted Answer

Maternal uniparental disomy

Question 7

Which of the following best explains why triploid plants are often sterile?

Accepted Answer

They cannot pair chromosomes evenly during meiosis, leading to unbalanced gametes.

Question 8

A cytogeneticist uses FISH (fluorescence in situ hybridization) to analyze a cancer cell line and observes chromosomes with multiple colors. What does this most likely indicate?

Accepted Answer

The chromosomes have undergone rearrangements such as translocations.

Question 9

Which of the following equations correctly represents the chromosome number in a human with Turner syndrome?

Accepted Answer

$$2n-1$$

Question 10

A patient is found to have a deletion on one chromosome that unmasks a recessive allele on the homologous chromosome, resulting in a dominant-like phenotype. What is this phenomenon called?

Accepted Answer

Pseudodominance

Question 11

Which of the following best describes the genetic mechanism underlying Angelman syndrome?

Accepted Answer

Loss of maternally expressed genes on chromosome 15

Question 12

In a cross between two plant species, a sterile hybrid is produced. Chromosome doubling occurs, resulting in a fertile new species. What is this process called?

Accepted Answer

Allopolyploidy

Question 13

Which of the following is a likely consequence of a paracentric inversion during meiosis in a heterozygote?

Accepted Answer

Formation of a dicentric bridge and acentric fragment

Question 14

A human cell is found to have 45 chromosomes, including only one X chromosome and no Y chromosome. Which syndrome does this individual most likely have?

Accepted Answer

Turner syndrome

Question 15

Which of the following best explains why polyploidy is more common and better tolerated in plants than in animals?

Accepted Answer

Plants can often reproduce asexually and tolerate gene dosage changes.

Question 16

Which of the following is a real-world example of an allopolyploid crop species?

Accepted Answer

Triticale

Question 17

A patient’s karyotype shows a cross-shaped structure during meiosis. What chromosomal abnormality is most likely present?

Accepted Answer

Reciprocal translocation

Question 18

Which of the following best describes the process of trisomy rescue?

Accepted Answer

A trisomic zygote loses one chromosome, potentially resulting in uniparental disomy.

Question 19

Which of the following is a likely outcome of a balanced reciprocal translocation in a carrier individual?

Accepted Answer

No phenotypic effect but increased risk of unbalanced gametes

Question 20

Which of the following best explains the increased risk of Down syndrome with advanced maternal age?

Accepted Answer

Increased rate of meiotic nondisjunction in oocytes as women age

Large-Scale Chromosomal Changes: Structure, Variation, and Consequences

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