This set of Basic Cell Biology Questions and Answers focuses on “Gene Expression Control – Aberrations and Disorders”.
1. Mutations in which of the following genes lead to a rare form of muscular dystrophy?
Explanation: Lamin makes up the inner surface of a nuclear membrane. Mutations in the lamin genes (LMNA) lead to a rare form of muscular dystrophy (EDMD2). Patients of this disease have extremely fragile nuclei.
2. Most alterations in the genes occur during ____________________
a) cell division
c) anaerobic conditions
d) sunlight exposure
Explanation: There are mutations that alter the information of a single gene and then there are a whole range of alterations that chromosomes may be subjected to. Most of these alterations occur during cell division, when the chromosomal content is replicated and then distributed evenly among daughter cells.
3. The chromosomal aberrations follow _____________________
a) chromosomal breakage
Explanation: The chromosomal aberrations follow chromosomal breakage; hence their incidence increases by exposure to agents such as UV-rays, X-rays, viral infections that damage the DNA.
4. Which of the following is a rare genetic disorder?
c) Fanconi anemia
d) Breast cancer
Explanation: Fanconi anemia is a rare genetic disorder in which the chromosomes are highly unstable and prone to breakage. This disease results in decreased production of all types of blood cells.
5. Which is not a type of chromosomal aberration?
Explanation: Chromosomal aberration refers to the change in number of chromosomes or any other associated errors. There are various types of chromosomal aberrations including inversions, translocations, duplications etc. Mutation however is a broader term.
6. Inversions can lead to a deletion or duplication in the chromosome.
Explanation: Inversions are chromosomal aberrations that occur when there are two breaks in the chromosome and the segment amidst the breaks becomes resealed in a reverse orientation. During crossing over the aberrant chromosome does not pair properly with its homologue, the gametes then generated by meiosis either possess duplication or a deletion.
7. The Philadelphia chromosome is the best studied example of ________________
Explanation: Philadelphia chromosome is the best studied example of translocation. It is a chromosome found in the malignant cells of leukemia patients. The Philadelphia chromosome was discovered in 1990 and is a shortened version of human chromosome 22.
8. The translocated part of Philadelphia chromosome is found on chromosome ________
Explanation: The translocated part of Philadelphia chromosome i.e. shortened chromosome 22 is found on chromosome 9, which gets an addition of 600 extra amino acids encoding for protein kinase.
9. Zygotes containing chromosomal deletion are produced by ___________
b) abnormal mitosis
c) abnormal meiosis
Explanation: Meiosis is the cellular process where a single cell divides twice to give rise to 4 distinct cells, the gametes. Zygotes containing a chromosomal deletion are a product of abnormal meiosis.
10. Unlike the 23 pairs of chromosomes in human cells, chimpanzees have 24 pairs of chromosomes.
Explanation: Translocations have been proved to be important evolutionary agents. The 24 pairs of chromosomes present in chimpanzees, gorillas, and orangutans reveal striking similarity with the 23 pairs of chromosomes present in human cells.
11. When was the first correlation between a chromosomal deletion and human disorder first developed?
Explanation: The first correlation between a chromosomal deletion and a human disorder was first discovered in 1963 by Jerome Lejeune, a French geneticist who had earlier discovered the chromosomal basis of Down syndrome.
12. Partial trisomy is the presence of _____ copies of a gene.
Explanation: Duplication occurs due to the presence of more copies of a gene than normal. Partial trisomy is the condition where a gene is repeated thrice, in place of two normal copies of the gene there are three copies.
13. The cry-of-the-cat syndrome is due to a defect in chromosome __________
Explanation: The cry-of-the-cat syndrome arises due to a deletion in human chromosome 5. This was elucidated by Jerome Lejeune while he observed a newborn with facial malformations and a cry resembling that of a suffering cat.
Sanfoundry Global Education & Learning Series – Cell Biology.
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