In this part, MCQs are based on chromosome duplication, deletion, Aneuploidy, Euploidy, cell cycle, division and its stages.

1. Which of the following could be due to duplication?
(a) Co-dominance
(b) Dominance
(c) Incomplete dominance
(d) Pleiotropy
Ans. (d) Pleiotropy
2. If there are two sequences CGCGCGCG and ATATATAT, which will have a higher probability of being duplicated?
(c) Both will have equal probability
(d) Both are unlikely to be duplicated
Ans. (c) Both will have equal probability
Explanation: Streisinger model works on repeated sequences, it is not base specific. In this case both the AT rich and CG rich sequences should have an equal probability of getting duplicated.
3. Which human chromosomes are involved in Down’s syndrome?
(a) 6
(b) 14 and 21
(c) 8 and 12
(d) X and Y
Ans. (b) 14 and 21
Explanation: In Down’s syndrome a part of the 21st chromosome’s long arm duplicates and transfers to chromosome 14’s long arm.
4. During Strisinger’s model, what happens?
(a) The Ribosome slips which causes duplication
(b) Parent strand slippage polymerase
(c) Daughter strand slippage polymerase
(d) The polymerase back tracks and resynthesizes
Ans. (c) Daughter strand slippage polymerase
5. How will you recognize a terminal deletion from breakage and loss at the terminal end?
(a) Indistinguishable
(b) Terminal break will lead to shorter chromosome than that due to chunk deletion
(c) Terminal break will be sticky
(d) Deletion will be recognized by trans factors
Ans. (c) Terminal break will be sticky
6. What will be the effect of the deletion mutation of a gene at the telomere?
(a) Organism will dye
(b) Organism will develop serious hazards due to absence of the gene and its product
(c) Mild effect on the phenotype
(d) No effect
Ans. (d) No effect
Explanation: The genes at the telomere are silenced, and never expressed. It is in form of heterochromatin inaccessible to the transcription machinery. Thus, deletion of a gene that wasn’t expressed to start with doesn’t make much difference.
7. Which of the following is not a possible cause of lethality of individuals carrying a deletion mutation?
(a) Genes that are not haplo sufficient doesn’t produce adequate gene product
(b) Genomic imbalance
(c) Unmasking of lethal recessive alleles
(d) Lack of diversity
Ans. (d) Lack of diversity
Explanation: lack of diversity affects at population level not at individual level. It is no cause for lethality of individuals with deleterious mutation.


8. The appearance of a recessive phenotype due to deletion of dominant gene is called?
(a) Hemi-dominance
(b) Pseudo dominance
(c) Imperfect dominance
(d) Co-dominance
Ans. (b) Pseudo dominance
Explanation: Pseudo dominance is the condition when the recessive allele is expressed in deletion mutation of dominant.
9. Yellow colour of mouse is generated by _________ mutation.
(a) Duplication
(b) Deletion
(c) Inversion
(d) Translocation
Ans. (b) Deletion
10. Deletion of a region led to over expression of a gene X. What do you conclude from this observation?
(a) Part of gene X is mutated
(b) Promoter of gene X is deleted
(c) Regulator of gene X is deleted
(d) No effect on gene X or its regulators
Ans. (c) Regulator of gene X is deleted
11. Euploidy leads to chromosomal variation in?
(a) Position
(b) Structure
(c) Number
(d) Size
Ans. (c) Number
12. A male bee can’t have a________________
(a) Mother
(b) Father
(c) Grandfather
(d) Grand mother
Ans. (c) Grandfather
Explanation: Since a male bee is produced from the unfertilized eggs by parthenogenesis, thus it will have a mother but not a father.
13. Which of the following will be sterile?
(a) Tetraploid
(b) Triploid
(c) Diploid
(d) Monoploid
Ans. (b) Triploid
Explanation: Tiploids are inherently sterile; this is due to the problem in meiosis that can produce a diploid and uniploid.
14. Colchicine is used to cause______________
(a) Mitotic non-disjunction
(b) Meiotic non-disjunction
(c) Mitotic disjunction
(d) Meiotic disjunction
Ans. (a) Mitotic non-disjunction
Explanation: Colchinine causes an arrest in anaphase which leads to mitotic non-disjunction halting the mitosis. This leads to doubling of chromosome as the duplicated chromatins fail to separate.
15. Which of the following pairing will not occur during meiosis of tetraploid?
(a) Two bivalent
(b) One bivalent and two univalent
(c) Trivalent and univalent
(d) Quadrivalent
Ans. (b) one bivalent and two univalent


16. Normal wheat Triticum aestivum is?
(a) Monoploid
(b) Tetraploid
(c) Pentaploid
(d) Hexaploid
Ans. (d) Hexaploid
16. In cells the DNA replication takes place in _____________ phase.
(a) G0
(b) G1
(c) S
(d) G2
Ans. (c) S
Explanation: Nullisomy results in (2n-2) set of chromosome, here n=7, so it will result in 12 chromosome over all.


17. The cells before permanently differentiating enters into ______________ phase.
(a) G1
(b) G2
(c) G0
(d) S
Ans. (c) G0
18. Aneuploidy is usually deleterious because:
(a) Chromosomal pairing is hampered
(b) Gene balance is disrupted
(c) Size of individual may vary
(d) Chromosomal disintegration is increased
Ans. (b) Gene balance is disrupted
19. Extreme klinefelter is an example of:
(a) Monosomy
(b) Trisomy
(c) Disomy
(d) Tetrasomy
Ans. (d) Tetrasomy
Explanation: In extreme klinefelter the chromosomal constitution is 44+XXXY, there are two extra X chromosomes which leads to more severe Klinefelter condition. Thus, it is tetrasomy.
20. Which of the following is resultant formation of Sexual mosaics?
(a) Female from male egg
(b) Gynandromorph
(c) Klinefelter
(d) Trisomy
Ans. (b) Gynandromorph

21. Which of the following Chromosome (trisomy) leads to Edward’s syndrome.
(a) 12
(b) 13
(c) 18
(d) 21
Ans. (c) 18
22. A non-disjunction in the 1st phase of meiosis will lead to _____________
(a) Monosomy
(b) Nullysomy
(c) Disomy
(d) Trtrasomy
Ans. (b) Nullysomy
23. The probability of aneuploidy in offspring increases with age as _________________
(a) Chromosomes tend to lose information with age
(b) Pairings at dichtyotene stages are gradually lost
(c) Ability of fertilization with age is gradually lost
(d) Chromosomal aberration with age
Ans. (b) Pairings at dichtyotene stages are gradually lost
24. Patau syndrome is a result of which of the following?
(a) Non-disjunction of sex chromosome in female
(b) Non- disjunction of sex chromosome in male
(c) Non-disjunction of chromosome 21
(d) Non-disjunction of chromosome 13
Ans. (d) Non-disjunction of chromosome 13
Explanation: Non-disjunction of chromosome 13 will result in a trisomy and monosomy if the gamete is fertilized. This results in Pataeu syndrome. It is an autosomal aneuploidy.
25. Farmers often practice polyploidy as _____________
(a) It makes the plants more durable
(b) They take longer time to undergo meiosis
(c) It increases complexity and there is a hope of new species
(d) It produces larger plant parts and products
Ans. (d) It produces larger plant parts and products
26. If an organism has 14 chromosomes, the number of chromosome generated by nullisomy will be?
(a) 15
(b) 7
(c) 13
(d) 12
Ans. (d) 12


27. Turner’s syndrome is a result of which of the following?
(a) Nullisomy
(b) Monosomy
(c) Trisomy
(d) Polysomy
Ans. (b) Monosomy
28. Eggs in female stay in ______________ phase for extended duration.
(a) S
(b) G1
(c) G2
(d) M
Ans. (d) M
Explanation: Eggs are stored for long in the ovary in the diplotene stage of meiosis 1 known as dichtyotene. Then the chromosomes are paired according to the homologous pairing.
29. Which of the following will prevent cell cycle from progressing in case of DNA damage unless the damage is repaired?
(a) P53
(b) G1 cyclin
(c) P10
(d) Bcl-2
Ans. (a) P53
30. The concentration of which of the following varies during the cell cycle?
(a) Cdk
(b) Cyclin
(c) SCF
(d) Proteosome
Ans. (b) Cyclin
Explanation: Cyclin regulates the phosphorylation and activation of the remaining participants bringing about cell cycle.
31. Which of the following is an activation process?
(a) Wee1 kinase
(b) APC
(c) Cdc25
(d) p27 binding
Ans. (c) Cdc25
Explanation: Cdc25 is a phosphatase, it activates Cyclin-Cdk. Other processes are inhibitory.
32. When the cell treated with hydroxyl urea and caffeine in G1 phase, the fate will be?
(a) Cell will not divide
(b) Cell will become smaller in size
(c) Cell will divide with improper chromosome number
(d) Cell will undergo lysis
Ans. (c) Cell will divide with improper chromosome number
Explanation: Hydroxyurea prevents DNA replication. When this is coupled with caffeine it leads to improper chromosome distribution among the daughter cells.
33. P53 prevents cell cycle progression during DNA damage requires ________________for its activity.
(a) Securin
(b) MCM
(c) Mdm
(d) Cdt
Ans. (c) Mdm
34. Mitosis occurs in which of the following?
(a) Nephron
(b) Hair follicles
(c) Neurons
(d) Ovary
Ans. (b) Hair follicles
Explanation: Mitosis occurs in proliferative somatic cells, nephron and neurons don’t proliferate. In ovary, oogenesis takes place via meiosis.
35. Cohesin brings two chromosomes together during synapsis, whereas chromosomal compaction is brought about by ________
(a) Cohesin
(b) Thrombin
(c) Condensin
(d) Sequrin
Ans. (c) Condensin
36. _________________ follows __________________
(a) Karyokinesis, Cytokinesis
(b) Cytokinesis, Karyokinesis
(c) Mitosis, Karyokinesis
(d) Karyokinesis, mitosis
Ans. (b) Cytokinesis, Karyokinesis
37. When a permanent cell re-enters cell cycle it is called as?
(a) Differenciation
(b) Redifferenciation
(c) Dedifferenciation
(d) Apoptosis
Ans. (c) Dedifferenciation
Explanation: Differenciation is the process by which a mitotic cell becomes permanent, while dedifferenciation is the reverse. Re-differenciation is the differenciation of the de-diffenenciated cell.
38. Cdc20___________________ anaphase.
(a) Slows
(b) Prevents
(c) Promotes
(d) not related
Ans. (c) Promotes
Explanation: Since Cdc20 is a cell cycle component it promotes anaphase by decreasing the M-Cdk level and also leading to breakdown to cohesion.
39. Suppose that chromosome is submetacentric, what will be the anaphase shape while separation?
(a) I
(b) J
(c) L
(d) V
Ans. (c) L
Explanation: During anaphase separation the chromatins are under a force, they tend to form L shaped structure if they are metacentric. I, J and V structures are formed by telocentric, acrocentric and metacentric chromosomes respectively.
40. Anaphase is brought about by the change in which cytoskeletal element?
(a) Dyanin
(b) Actin
(c) Myosin
(d) Tubulin
Ans. (d) Tubulin
41. If mitotic cell, which of the following doesn’t take place in prophase?
(a) Chromosome starts to contract
(b) The nuclear membrane breaks down
(c) The nucleolus disappears
(d) The chromosomes pair up with their homologue
Ans. (d) The chromosomes pair up with their homologue
42. Which of the following cell division phases prevented when colchicine is used?
(a) Prophase
(b) Telophase
(c) Anaphase
(d) DNA replication
Ans. (c) Anaphase
Explanation: Colchicine disrupts the microtubule structure which leads to the absence of anaphase.
43. In haploid organism meiosis takes place in _____________
(a) Somatic cell
(b) Zygote
(c) Gamete
(d) Egg
Ans. (b) Zygote
Explanation: Here, egg and other gamete are haploid as is somatic cell, so no meiosis is required by it. In haploid organisms the zygote is diploid which undergoes meiosis to give a haploid individual.
44. Which of the following is reduction division of mitosis?
(a) The 1st division
(b) The 2nd division
(c) Both a & b
(d) The telophase
Ans. (a) The 1st division
45. Choose the correct one for pre-leptotene phase?
(a) Chromosome compaction
(b) Pairing of homologous
(c) Marked increase in nuclear volume
(d) Disappearance of nuclear membrane
Ans. (c) Marked increase in nuclear volume
46. In which of the following, the leptotene Bouquet stage is seen?
(a) Insect
(b) Bacteria
(c) Yeast
(d) Plants
Ans. (a) Insect
Explanation: In animals and particularly in insects during leptotene stage the chromosomes have their ends drawn to a point forming a bouquet structure near the centriole. Because plants lack centriole it is not seen in plants.
47. Choose the false one for leptotene phase?
(a) It is a short phase
(b) Chromosomes have beads on a string appearance
(c) Longitudinal double nature of chromosome starts to appear
(d) Bouquet like structure is formed
Ans. (c) Longitudinal double nature of chromosome starts to appear
48. Which of the following is directly correlated to polyribosomal synthesis in leptotene stage?
(a) RNA synthesis
(b) Protein synthesis
(c) Protein turnover
(d) Protein function
Ans. (d) Protein function
49. Which of the following is true?
(a) Zygotene is the phase preceding diplotene
(b) DNA replicated in zygotene is incorporated in chromosome 5-6 days later
(c) Synaptonemal complex formed is longer than the physical length of chromosomes itself
(d) The pairing of chromosomes forces the DNA to replicate
Ans. (b) DNA replicated in zygotene is incorporated in chromosome 5-6 days later
50. The formation of synaptonemal complex in zygotene is ______________ DNA replication.
(a) Before
(b) Simultaneous
(c) After
(d) None of these
Ans. (c) After

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