Chromosomal Aberrations Practice Questions
20 free Chromosomal Aberrations practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Chromosomal aberrations are defined as:
- A Changes restricted to the nucleotide sequence of a gene
- B Structural or numerical changes in chromosomes
- C Errors introduced during transcription of mRNA
- D Alterations affecting RNA processing and splicing
Correct answer: Structural or numerical changes in chromosomes
Chromosomal aberrations are changes in chromosome structure (e.g., deletion, duplication, inversion, translocation) or number (e.g., aneuploidy, polyploidy). They typically arise from errors during cell division or from unrepaired DNA damage.
Which of the following is an example of a structural chromosomal aberration?
- A Aneuploidy
- B Polyploidy
- C Chromosomal deletion
- D Nondisjunction
Correct answer: Chromosomal deletion
Deletion is a structural aberration in which a segment of a chromosome is lost. The remaining chromosome is therefore missing the genes carried by the deleted segment, often causing severe developmental effects.
Loss of a segment of a chromosome results in which type of aberration?
- A Duplication
- B Chromosomal deletion
- C Inversion
- D Translocation
Correct answer: Chromosomal deletion
Deletion occurs when a chromosome loses a segment, resulting in the absence of all genes located in that region. This structural aberration frequently leads to loss of essential genetic information and serious phenotypic consequences.
Duplication of a chromosomal segment leads to:
- A Loss of genetic material from the genome
- B Increase in gene dosage
- C Change in total chromosome number
- D Formation of polyploid cell lines
Correct answer: Increase in gene dosage
Duplication results in repetition of a chromosomal segment. This increases gene dosage, which can disturb normal cellular balance.
Inversion is best described as:
- A Transfer of chromosome segment to another chromosome
- B Loss of chromosome segment
- C Reversal of a chromosome segment
- D Addition of extra chromosome
Correct answer: Reversal of a chromosome segment
In inversion, a chromosome segment breaks and reinserts in reverse orientation. This alters gene order without changing gene content.
Which chromosomal aberration involves exchange of segments between non-homologous chromosomes?
- A Segment reversal within one chromosome
- B Segment loss from one chromosome
- C Segment repetition on one chromosome
- D Segment exchange between chromosomes
Correct answer: Segment exchange between chromosomes
Translocation occurs when chromosome segments are exchanged between non-homologous chromosomes. It can disrupt gene function.
Numerical chromosomal aberrations mainly arise due to:
- A Crossing over
- B Mutation
- C Nondisjunction
- D DNA replication
Correct answer: Nondisjunction
Nondisjunction is the failure of chromosomes to separate properly during cell division. It results in abnormal chromosome numbers.
Aneuploidy refers to:
- A Gain or loss of entire chromosome sets
- B Gain or loss of one or few chromosomes
- C Structural alteration of chromosomes
- D Duplication of chromosome segments
Correct answer: Gain or loss of one or few chromosomes
Aneuploidy involves the addition or loss of individual chromosomes. It disrupts normal chromosome balance.
Which condition is an example of aneuploidy in humans?
- A Triploidy
- B Tetraploidy
- C Down syndrome
- D Polyploidy in plants
Correct answer: Down syndrome
Down syndrome is caused by trisomy of chromosome 21. It represents a classic example of aneuploidy.
Polyploidy is characterized by:
- A Loss of one chromosome from the genome
- B Gain of a single chromosome segment only
- C More than two complete sets of chromosomes
- D Exchange of segments between homologous chromosomes
Correct answer: More than two complete sets of chromosomes
Polyploidy involves having more than two complete sets of chromosomes. It is common in plants but rare in animals.
Which chromosomal aberration is often lethal when occurring in autosomes?
- A Duplication of a segment
- B Gene deletion
- C Balanced translocation
- D Pericentric inversion
Correct answer: Gene deletion
Deletion leads to loss of essential genes. Large deletions in autosomes often result in lethality.
Balanced translocation usually does not show phenotypic effects because:
- A All genes are duplicated in both segments
- B Only non-essential genes are deleted
- C No net loss or gain of genetic material occurs
- D Chromosome number remains exactly unchanged
Correct answer: No net loss or gain of genetic material occurs
In balanced translocation, genetic material is rearranged without loss or gain. Hence, phenotype often remains normal.
Which stage of cell division is most critical for preventing numerical chromosomal aberrations?
- A Prophase
- B Metaphase
- C Anaphase
- D Telophase
Correct answer: Anaphase
During anaphase, chromosomes or chromatids separate properly. Errors at this stage can lead to nondisjunction.
Chromosomal aberrations can be caused by exposure to:
- A Increased metabolic rate in cells
- B Heritable genetic disorders
- C Improved organism adaptability
- D Enhanced rate of cell division
Correct answer: Heritable genetic disorders
Chromosomal aberrations can disrupt gene balance. This often results in genetic disorders and developmental abnormalities.
Which chromosomal aberration alters gene order but not gene number?
- A Deletion
- B Duplication
- C Inversion
- D Aneuploidy
Correct answer: Inversion
Inversion changes the orientation of genes within a chromosome. The total gene content remains unchanged.
The major consequence of chromosomal aberrations at the organism level is:
- A Increased metabolic rate
- B Genetic disorders
- C Improved adaptability
- D Enhanced cell division
Correct answer: Genetic disorders
Chromosomal aberrations can disrupt gene balance. This often results in genetic disorders and developmental abnormalities.
Which chromosomal abnormality is more tolerated in plants than animals?
- A Aneuploidy
- B Deletion
- C Polyploidy
- D Inversion
Correct answer: Polyploidy
Polyploidy is common and often beneficial in plants. In animals, it usually leads to severe abnormalities.
Which technique is commonly used to detect chromosomal aberrations?
- A PCR
- B Gel electrophoresis
- C Karyotyping
- D DNA sequencing
Correct answer: Karyotyping
Karyotyping allows visualization of chromosomes. It helps detect changes in chromosome number and structure.
Structural chromosomal aberrations mainly affect:
- A Chromosome number
- B Gene arrangement
- C RNA synthesis
- D Protein folding
Correct answer: Gene arrangement
Structural aberrations change the arrangement of genes on chromosomes. This can disrupt normal gene expression.
Overall, chromosomal aberrations highlight the importance of:
- A Accuracy of protein synthesis in cells
- B Fidelity of DNA replication each cycle
- C Proper chromosome segregation during division
- D Specificity of enzyme-substrate interactions
Correct answer: Proper chromosome segregation during division
Accurate segregation of chromosomes during cell division is essential. Errors can lead to serious chromosomal abnormalities.