CBSE Class 12 Biology Molecular Basis of Inheritance MCQs Set 04

Biology Objective Questions and Answers: Chapter 05 Molecular Basis of Inheritance

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Question: Diploid chromosome number in humans is 
a) 46 
b) 44
c) 48 
d) 42 
Answer: A

Question: DNA replication is  
a) conservative and discontinuous 
b) semi-conservative and semi-discontinuous 
c) semi-conservative and discontinuous 
d) conservative 
Answer: A
 
Question: Both husband and wife have normal vision though their fathers were colourblind. The probability of their daughter becoming colourblind is  
a) 0% 
b) 25% 
c) 50%
d) 75%
Answer: A
 
Question: Haemophilia is more common in males because it is a  
a) recessive character carried by Y-chromosome 
b) dominant character carried by Y-chromosome 
c) dominant trait carried by X-chromosome 
d) recessive trait carried by X-chromosome 
Answer: D
 
Question: Which one is a hereditary disease?  
a) Cataract
b) Leprosy 
c) Blindness 
d) Phenylketonuria
Answer: D
 
Question: A colourblind girl is rare because she will be born only when  
a) her mother and maternal grandfather were colourblind 
b) her father and maternal grandfather were colourblind 
c) her mother is colourblind and father has normal vision 
d) parents have normal vision but grand parents were colourblind 
Answer: B
 
Question: The process of transfer of genetic information from DNA to RNA/formation of RNA from DNA is  
a) trnsversion 
b) transcription 
c) translation
d) translocation
Answer: B
 
Question: Escherichia coli fully labelled with N15 is allowed to grow in N14 medium. The two strands of DNA molecule of the first generation bacteria have 
a) different density and do not resemble parent DNA 
b) different density but resemble parent DNA 
c) same density and resemble parent DNA 
d) same density but do not resemble parent DNA
Answer: B
 
Question: Khorana first deciphered the triplet codons of  
a) serine and isoleucine 
b) threonine and histidine 
c) tyrosine and tryptophan 
d) phenylalanine and methionine
Answer: B
 
Question: Experimental material in the study of DNA replication has been  
a) Escherichia coli 
b) Neurospora crassa 
c) Pneumococcus 
d) Drosophila melanogaster
Answer: A
 
Question: Out of 8 ascospores formed in Neurospora the arrangement is 2a : 4a : 2a showing 
a) no crossing over
b) some meiosis
c) second generation division
d) first generation division
Answer: C
 
Question: Down’s syndrome is due to 
a) crossing over
b) linkage
c) sex-linked inheritance
d) non-disjunction of chromosomes
Answer: D
 
Question: A colourblind mother and normal father would have 
a) colourblind sons and normal/carrier daughters
b) colourblind sons and daughters
c) all colourblind
d) all normal
Answer: A
 
Question: In human beings 45 chromosomes/single X/XO abnormality causes 
a) Down’s syndrome
b) Klinefelter’s syndrome
c) Turner’s syndrome
d) Edward’s syndrome
Answer: C
 
Question: Of a normal couple, half the sons are haemophilic while half the daughters are carriers. The gene is located on 
a) X-chromosome of father
b) Y-chromosome of father
c) one X-chromosome of mother
d) both the X-chromosomes of mother
Answer: C
 
Question: Sex is determined in human beings 
a) by ovum
b) at the time of fertilization
c) 40 days after fertilization
d) seventh to eight week when genitals differentiate in foetus
Answer:B
 
Question: Mr. Kapoor has Bb autosomal gene pair and d allele sex-linked. What shall be proportion of Bd in sperms? 
a) 0
b) 1/2
c) 1/4 
d) 1/8
Answer: C
 
Question: Of both normal parents, the chance of a male child becoming colourblind are 
a) no
b) possible only when all the four grand parents had normal vision
c) possible only when father’s mother was colourblind
d) possible only when mother’s father was colourblind
Answer: D
 
Question: The transforming principle of Pneumococcus as found out by Avery, MacLeod and McCarty was
a) mRNA 
b) DNA 
c) protein
d) polysaccharide
Answer: B
 
Question: Because most of the amino acids are represented by more than one codon, the genetic code is 
a) overlapping
b) Wobbling
c) degenerate 
d) generate
Answer: C
 
Question: Who proved that DNA is basic genetic material?
a) Griffith
b) Watson
c) Boveri and Sutton
d) Hershey and Chase
Answer: D
 
Question: During DNA replication, the strands separate by 
a) DNA polymerase
b) topoisomerase
c) unwindase/helicase
d) gyrase
Answer: C
 
Question: The process of translation is 
a) ribosome synthesis
b) protein synthesis
c) DNA synthesis
d) RNA synthesis
Answer: B
 
Question: A DNA with unequal nitrogen bases would most probably be 
a) single stranded
b) double stranded
c) triple stranded
d) four stranded
Answer: A
 
Question: Nucleosome core is made of 
a) H1, H2A, H2B and H3
b) H1, H2A, H2B, H4
c) H1, H2A, H2B, H3 and H4
d) H2A, H2B, H3 and H4
Answer: D
 
Question: Initiation codon of protein synthesis (in eukaryotes) is 
a) GUA
b) GCA
c) CCA 
d) AUG
Answer: D
 
Question: The number of base substitution possible in amino acid codons is 
a) 261
b) 264
c) 535 
d) 549
Answer: D
 
Question: Reverse transcriptase is 
a) RNA dependent RNA polymerase
b) DNA dependent RNA polymerase
c) DNA dependent DNA polymerase
d) RNA dependent DNA polymerase
Answer: D
 
Question: In Escherichia coli lac Operon is induced by
a) lactose 
b) promoter gene
c) β-galactosidase
d) I-gene
Answer: A
 
Question: DNA template sequence of CTGATAGC is transcribed over mRNA as 
a) GUCTUTCG 
b) GACUAUCG
c) GAUTATUG
d) UACTATCU
Answer: B
 
Question: Protein helping in opening of DNA double helix in front of replications fork is 
a) DNAgyrase 
b) DNA polymerase-I
c) DNAligase
d) topoisomerase
Answer: A
 
Question: Which is not involved in protein synthesis?
a) Transcription 
b) Initiation
c) Elongation
d) Termination
Answer: A
 
Question: Genes located on Y-chromosome are 
a) mutant genes
b) sex-linked genes
c) autosomal genes
d) holandric genes
Answer: D
 
Question: A colourblind woman marries a normal visioned male. In the offspring 
a) both son and daughter are colourblind
b) all daughters are colourblind
c) all sons are normal
d) all sons are colourblind
Answer: D
 
Question: Out of A=T, G =C pairing, bases of DNA may exist in alternate valency state owing to arrangement called 
a) analogue substitution
b) tautomerizational mutation
c) frameshift mutation
d) point mutation
Answer: B
 
Question: The wild type E. coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as sugar. Which of the following changes takes place? 
a) The lac operon is repressed
b) All operons are induced
c) The lac operon is induced
d) E. coli cells stop dividing
Answer: C
 
Question: Anticodon is an unpaired triplet of bases in an exposed position of 
a) mRNA
b) rRNA
c) tRNA 
d) sRNA
Answer: C
 
Question: If the sequence of bases in DNA is ATTCGATG, then the sequence of bases in its transcript will be 
a) CAUCGAAU
b) UAAGCUAC
c) GUAGCUUA
d) AUUCGAUG
Answer: B
 
Question: In split genes, the coding sequence are called
a) introns
b) operons
c) exons 
d) cistrons
Answer: C
 
Question: The change of the light coloured variety of peppered moth (Biston betularia) to its darker variety (Biston carbonarid) is due to 
a) mutation
b) regeneration
c) genetic isolation
d) temporal isolation
Answer: A
 
Question: The polytene chromosomes were discovered for the first time in 
a) Drosophila 
b) Chironomus
c) Musca nebulo
d) Musca domestica
Answer: B
 
Question: The most striking example of point mutation is found in a disease called 
a) thalassemia
b) night blindness
c) Down’s syndrome
d) sickle cell anaemia
Answer: D
 
Question: Barr body in mammals represents 
a) all the heterochromatin in female cells
b) Y-chromosomes in somatic cells of male
c) all heterochromatin in male and female cells
d) one of the two X-chromosomes in somatic cells of females
Answer: D
 
Question: An individual exhibiting both male and female sexual characteristics in the body is known as 
a) hermaphrodite
b) intersex
c) gynandromorph
d) bisexual
Answer: C
 
Question: A person with 47 chromosomes due to an additional Y-chromosome suffers from a condition called
a) Down’s syndrome
b) Super female
c) Turner’s syndrome
d) Klinefelter’s syndrome
Answer: D
 
Question: The translation termination triplet is 
a) UAU 
b) UAA
c) UAC
d) UGC
Answer: B
 
Question: Okazaki fragments are seen during 
a) transcription
b) translation
c) replication 
d) transduction
Answer: C
 
Question: An enzyme that joins the ends of two strands of nucleic acid is a 
a) polymerase
b) synthetase
c) helicase 
d) ligase
Answer: D
 
Question: H. J. Muller was awarded Nobel Prize for his
a) discovery that chemicals can induce gene mutations
b) discovery that ionizing radiations can induce gene mutations
c) work on gene mapping in Drosophila
d) efforts to prevent the use of nuclear weapons
Answer: B
 
Question: After crossing two plants, the progenies are found to be male sterile. This phenomenon is found to be maternally inherited and is due to some genes which are present in
a) nucleus 
b) chloroplast
c) mitochondria
d) cytoplasm
Answer: B

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Multiple Choice Questions (MCQs) for Class 12 Biology Chapter 05 Molecular Basis of Inheritance

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