This part includes about mcqs on chromosome and chromosomal abnormalities.

1. The term chromosome was coined by:
(a) T.H Morgan
(b) Sutton & Boveri
(c) Waldeyer
(d) Hoffmeister
Ans: (c) Waldeyer


2. Which of the following chromosomes found in the salivary gland of Drosophila:
(a) Polytene
(b) Lampbrush
(c) Supernumerary
(d) All of these
Ans: (a) Polytene.

3. Lampbrush chromosomes occur in:
(a) Oocytes
(b) Cancer cells
(c) Lymph glands
(d) Salivary glands
Ans: (a) Oocytes.


4. Choose the true one about the Chromatids?
(a) It is a haploid chromosome
(b) It is a complete chromosome
(c) It is a duplicate chromosome
(d) It is one-half of the replicated chromosomes
Ans: (d) It is one-half of the replicated chromosomes

5. The centromere is that part of chromosome where:
(a) Nicking occurs
(b) Chromatids are attached
(c) Nucleoli are formed
(d) Crossing-over takes place
Ans: (b) Chromatids are attached

6. The ends of the chromosome are called:
(a) Gene
(b) Centromeres
(c) Telomeres
(d) Kinetochore
Ans: (c) Telomeres.

7. Chromosomes were first observed by which scientist:
(a) Fleming
(b) Waldeyer
(c) Strasburger
(d) Hoffmeister
Ans: (d) Hoffmeister.

8. A chromosome with sub-terminal centromere is called?
(a) Acrocentric
(b) Acentric
(c) Metacentric
(d) Telocentric
Ans: (a) Acrocentric.

9. The giant chromosome with a number of chromonemeta is:
(a) Hetrochromosome
(b) Polytene chromosome
(c) Lampbrush chromosome
(d) Supernumerary chromosome
Ans: (b) Polytene chromosome.

10. A chromosome with centromere near the middle is called?
(a) Metacentric
(b) Acrocentric
(c) Telocentric
(d) Submetacentric
Ans: (d) Submetacentric.

11. Puffs or balbiani rings in the salivary gland chromosome are the sites of:
(a) Protein synthesis
(b) RNA synthesis
(c) DNA replication
(d) DNA duplication
Ans: (b) RNA synthesis.

12. Chromosomal theory of inheritance was proposed by:
(a) Sutton in 1902
(b) Boveri in 1902
(c) Correns in 1909
(d) Sutton and Boveri in 1902
Ans: (d) Sutton and Boveri in 1902.


13. Which of the following doesn’t agree with the chromosomal theory of inheritance?
(a) The genes are located on the chromosome
(b) The genes on the same chromosome are always passed together
(c) The genes are located linearly on the chromosomes
(d) The distance between two genes can be mapped
Ans: (b) The genes on the same chromosome are always passed together

14. The chromosomal theory of inheritance violates which of the following laws?
a) Law of dominance
b) Law of segregation
c) Law of independent assortment
d) None
Ans: d) None


15. A colour blind daughter may be born if the:
(a) Father is normal and the mother is a carrier
(b) Father is normal and the mother is colour blind
(c) Father is colour blind and mother is a carrier
(d) Father is colour blind and mother is normal
Ans: (c) Father is colour blind and mother is a carrier.

16. A somatic cell in a human male contains:
(a) No gene on the sex chromosome
(b) Genes on only on sex chromosomes
(c) Two genes for every sex-linked character
(d) Only one sex-linked gene for each character
Ans: (d) Only one sex-linked gene for each character.

17. The blue-green algae and bacteria contain:
(a) Three linkage groups
(b) Two linkage groups
(c) One linkage group
(d) None of the above
Ans: (c) One linkage group.

18. What is the number of linkage groups in the Drosophila?
(a) Two
(b) Four
(c) Eight
(d) None of the above
Ans: (b) Four.


19. Gene for colour blindness in man is located on ___________.
(a) Both X and Y chromosome
(b) Y-chromosome only
(c) X-chromosome only
(d) Either X-chromosome or Y-chromosome
Ans: (c) X-chromosome only.

20. Chromosomal constitution in human females can be best written as?
(a) 46
(b) 44+2
(c) 44A+XY
(d) 44A+XX
Ans: (d) 44A+XX.

21. Which of the following disease is sex-linked?
(a) Hepatitis
(b) Leukaemia
(c) Malignancy
(d) Colour blindness
Ans: (d) Colour blindness.

22. If there is a non-disjunction in the X chromosome, the progeny being XXY, what will be the constitution of the chromosome(s) in the gamete?
(a) X and Y
(b) X and XY
(c) XX and Y
(d) XXY with no separation
Ans. (b) X and XY

23. You observe a genetic trait which is a common occurrence in the male of a particular pedigree, this is possibly a?
(a) X linked
(b) Y linked
(c) X linked recessive
(d) Y linked dominant
Ans: (b) Y linked

Explanation: If the gene has a sex bias it is certainly sex linked. In this case, it is a common occurance in the males only in a pedigree so it must be Y linked gene. There is no dominant recessive as Y is always hemizygous.
24. If you cross a red eyed pure breeding female Drosophila with a white eyed male, then the F1 males so produces were crossed with white eyed male, what will be the eye colour of their daughters and sons in F2?
(a) Both daughters and sons red eyed
(b) Daughters with both eye colour while sons with white eye
(c) Both daughters and sons with both eye colours
(d) Daughters with red eye and sons with white eyes
Ans. (d) Daughters with red eye and sons with white eyes
Explanation: Eye colour is a sex linked trait. In this following case, the F1 male progeny was red eyed, as the father only gave the Y chromosome and not X which determines eye colour. Then similarly the F2 sons would be white eyed by allele from their mother, female will be red eyed as they get both alleles.

25. If the genes are located in a chromosome as A—B—C—D—E—O—-T. Which of the gene pairs will have least probability of being inherited together?
(a) C and D
(b) A and T
(c) A and B
(d) O and T
Ans. (b) A and T
Explanation: Longer is the distance, lesser will be the probability of the two genes being inherited together as then there will be a greater chance of recombination.

26. If a gamete has 16 chromosomes, what will be the number of chromatids before anaphase 1?
(a) 8
(b) 16
(c) 32
(d) 64
Ans. (d) 64
Explanation: There are 32 chromosomes but they are in duplicate chromatids so 64 is the number of chromatids before anaphase 1.

27. Which of the following can result from non-disjunction?
(a) XY and XO
(b) YY and XY
(c) X and Y
(d) XY and XXY
Ans. (a) XY and XO

28. What is meant by degenerate codon?
(a) Two codons can be read in different frame o give different amino acids
(b) Codons are not having a gap
(c) Specific codon codes for specific amino acid
(d) Two codons can code for same amino acid

Ans. (d) Two codons can code for same amino acid
29. Consider that our codon in place of being triplet was quadruplet. How many possible combinations could be there then?
(a) 64
(b) 128
(c) 256
(d) 360
Ans. (c) 256
Explanation: There are 4 DNA bases and triplet coodon so number of possible combinations id 43=64. Now if the codon was quadruplet the combinations would be 44=256.

30. Which of the following is not a stop codon?
(a) UAA
(b) GUG
(c) UAG
(d) UGA
Ans. (b) GUG

31. Which of the following is not a type of translocation?
(a) Simple
(b) Reciprocal
(c) Tandem
(d) Intercalary
Ans. (c) Tandem

32. In translocating gene fragment which part is responsible for translocation?
(a) The LTR
(b) The transcribed gene
(c) The non-coding part of gene
(d) The surrounding sequences
Ans. (a) the LTR

33. Translocation in plants was discovered by?
(a) Stern
(b) Barbara McClintok
(c) Sutton and Boveri
(d) Morgan
Ans. (b) Barbara McClintok

34. Which of the following could result in homologous chromosomes moving to the same pole after anaphase 1?
(a) Doubling
(b) Inversion
(c) Breaking
(d) Translocation
Ans. (d) Translocation

35. Which of the following is a result of reciprocal translocation?
(a) Burkitt’s lymphpma
(b) Trychothiodystrophy
(c) Thalassemia
(d) Cockyne’s syndrome
Ans. (a) Burkitt’s lymphpma

36. Which of the following is mandatory for autonomous transposition?
(a) Internal gene
(b) Transposase
(c) 3’ concensus of region upstream to transposition
(d) Branch point A
Ans. (b) Transposase

37. What percentage of the human genome is transposition related?
(a) 2%
(b) 10%
(c) 50%
(d) 80%
Ans. (c) 50%

38. Choose the wrong one out for insertion sequence.
(a) Insertion sequences are transposons
(b) Insertion sequences range from 5kb to 30kb
(c) Insertion sequences only carry genes for their transposition
(d) Insertion sequences have terminal IR
Ans. (b) Insertion sequences range from 5kb to 30kb
Explanation: Insertion sequences are very short transposons which range from 768 bp to 5 kb.

39. Which of the following is wrong option?
(a) Transposons have trasposase along with other genes
(b) Transposons lack inverted terminal repeats
(c) Transposons have insertion sequences within it
(d) Class III transposons are called MITES
Ans. (b) Transposons lack inverted terminal repeats

40. Which of the following is not true about conservative transposition?
(a) It creates direct repeat sequences on either side
(b) It is Copy-Paste mechanism
(c) Transesterification reaction takes place
(d) Class II transposons have this mechanism
Ans. (b) It is Copy-Paste mechanism
Explanation: Conservative or non-replicative transposition acts through cut and paste mechanism. The donor site loses the transposon which is inserted in the recipient generating direct repeats. It is seen in class II transposons.
41. Which of the following enzyme is seen in copy-paste method, but not seen in cut-paste transposition?

(a) Resolvase
(b) Strand transfer
(c) Transposase
(d) Synaptic complex
Ans. (a) Resolvase

42. choose wrong one about Inversion:
(a) Inverted chromosomes are generally viable
(b) Inversion can cause chromosome breakage
(c) Two DNA strands with an inverted segment will not pair
(d) Inversion including centromere is known as pericentric
Ans. (c) Two DNA strands with an inverted segment will not pair

43. Consider this sequence A—O—B —C—D—E—F, be a DNA sequence where O is the centromere. Which of the following will be a pericentric inversion?
(a) A—O—B—D—E—F
(b) B—O—A—D—E—F
(c) D—B—O—A—E—F
(d) A—O—E—D—B—F
Ans. (d) A—O—E—D—B—F
Explanation: Pericentric inversion is the inversion that doesn’t involve the centromere. Here in option A there is no change at all, option B and C are including the centromere. Only option D doesn’t involve the centromere in the inverted sequence, so it is pericentric.

44. What are the results of pericentric inversion with single crossing over?
(a) Two normal, one dicentric and one acentric chromosome
(b) 2 dicentric and 2 acentric chromosomes
(c) Four normal chromosomes with centriomere in different positions
(d) 3 normal chromosome, one abnormal acentric chromosome
Ans. (a) Two normal, one dicentric and one acentric chromosome
Explanation: Recombination in the paracentric region will take place between only two strands, so the other two strands will be normal. This recombination will result in one dicentric chromosome and another acentric chromosome.

45. In drosophila male there is no cross over suppression due to pericentric inversion as:
(a) They have only one set of chromosome
(b) They always have double cross over
(c) They never recombine
(d) They don’t undergo meiosis
Ans. (c) They never recombine

46. Which of the following is an example of inversion?
(a) Chromosome 22 and 9
(b) Chromosome 8
(c) Chromosome 14
(d) Chromosome 3
Ans. (d) Chromosome 3
Explanation: In chromosome 3 of human there is duplication-deletion which leads to inversion.

47. In pericentric inversion, the inversion loop involves __________ strands.
(a) 1
(b) 2
(c) 3
(d) 4
Ans. (d) 4

48. Which of the following case of duplication involves more than one chromosome?
(a) Tandem duplication
(b) Reverse tandem duplication
(c) Displaced
(d) Transposed
Ans. (d) Transposed

49. Tandem duplication creates ____________ and reverse tandem creates_____________
(a) Buckling, looping
(b) Hairpin, buckling
(c) Buckling, Hairpin
(d) Loop with turn, hairpin
Ans. (c) Buckling, Hairpin
Explanation: In case of tandem repeat the same sequence in same order is repeated. As parent chromosome has only one copy of that sequence the daughter bulges out. This, causes buckling. In reverse tandem the duplication is inverted in sequence which leads to formation of hairpin.

50. Which of the following explains Streisinger’s model?
(a) Transition Frame shifts
(b) Transposition
(c) Inversion
(d) Frame shifts
Ans. (d) Frame shifts
Explanation: Streisinger’s model explains that the Frame shift mutations are more frequent in repetitive sequences. This causes duplicative insertion and also at times deletion.

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