CBSE Class 12 Biology Quiz | CBSE Class 12 Biology MCQs with Answers

Questions
101 ZIFT is transfer of
A zygote into fallopian tube.
B a mixture of sperms and ova into the fallopian tube.
C a mixture of sperms and ova into the uterus.
D embryo into the uterus.

Answer: zygote into fallopian tube.
102 Diaphragms are the contraceptive devices used by females. Choose the correct option about them.
A They are placed to cover the cervix.
B They block the entry of sperms.
C They are reusable.
D All of these.

Answer: All of these.

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103 When ‘Aa’ is crossed with ‘aa’, (A is dominant over a)
A all the offspring will have dominant phenotype.
B all the offspring will have recessive phenotype.
C 50% of offspring will have dominant phenotype and 50% will have recessive phenotype.
D 75% of offspring will have dominant phenotype and 50% will have recessive phenotype.

Answer: 50% of offspring will have dominant phenotype and 50% will have recessive phenotype.
104 The possibility of all genotypes of offspring in a genetic cross is calculated by a graphical representation which was developed by
A Gregor Mendel
B Reginald Punnett
C Komberg
D T.H. Morgan

Answer: Reginald Punnett
105 Study the pedigree chart given Select the correct option about the conclusion.
A It is a sex-linked recessive trait.
B It is an autosomal recessive trait.
C It is an autosomal dominant trait.
D It is a sex-linked dominant trait.

Answer: It is an autosomal recessive trait.
106 Mother and father of a person with ‘O’ blood group have ‘A’ and ‘B’ blood group respectively. What would be the genotype of both mother and father? [NCERT Exemplar]
A Mother is homozygous for ‘A’ blood group and father is heterozygous for ‘B’.
B Mother is heterozygous for ‘A’ blood group and father is homozygous for ‘B’.
C Both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively.
D Both mother and father are homozygous for ‘A’ and ‘B’ blood group, respectively.

Answer: Both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively.
107 If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is: [NCERT Exemplar]
A Sex-linked recessive.
B Sex-linked dominant
C Autosomal dominant
D Autosomal recessive

Answer: Sex-linked recessive.
108 In a dihybrid cross, if you get 9:3:3:1 ratio it denotes that: [NCERT Exemplar]
A It is a case of multiple allelism.
B The alleles of two genes are segregating independently.
C The alleles of two genes are interacting with each other.
D It is a multigenic inheritance.

Answer: The alleles of two genes are segregating independently.
109 Which of the following traits studied by Mendel in garden pea is a dominant trait?
A Inflated pod.
B Yellow colour of pod.
C Green colour of seed.
D Terminal flowers.

Answer: Inflated pod.
110 If a haemophilic woman marries a normal man,
A all their children will be normal.
B all their sons will be haemophilic.
C all their daughters will be haemophilic.
D 50% sons and 50% daughters will be haemophilic.

Answer: all their sons will be haemophilic.
111 Operon model for regulation of transcription was proposed by
A Meselson and Stahl
B Jacob and Monod
C Watson and Crick
D Hershey and Chase

Answer: Jacob and Monod
112 Eukaryotic RNA polymerase III catalyses the synthesis of
A tRNA
B hnRNA
C mRNA
D rRNA

Answer: tRNA
113 The sequence of nitrogen bases in a # segment of a coding strand of DNA is ’ AATGCTTAGGCA. What will be the sequence of nitrogen bases in the wRNA transcribed by it?
A UUA CGA AUC CGU
B AAU GCU UAG GCA
C AAU GCU AAC CGA
D AAU GCA AUC CGU

Answer: AAU GCU UAG GCA
114 Which of the following sets of codons contains only termination codons?
A UAA, UGA, UAG
B UUU, UCC, UGG
C UAA, UUU, UGG
D UAA, UAG, UAC

Answer: UAA, UGA, UAG
115 The central dogma of molecular biology (genetic information flow) was modified by the discovery of
A RNA polymerase
B DNA ligase
C Reverse transcriptase
D DNA polymerase

Answer: Reverse transcriptase
116 The human chromosome with the highest and least number of genes in them are respectively
A Chromosome 21 and Y
B Chromosome 1 and Y
C Chromosome X and Y
D Chromosome 1 and X

Answer: Chromosome 1 and Y
117 The net electric charge on DNA and histone, is
A positive, negative
B negative, positive
C positive, positive.
D negative, negative

Answer: negative, positive
118 In E.coli, the lac operon gets switched on when [NCERT Exemplar]
A lactose is present and it binds to the », repressor.
B repressor binds to operator.
C RNA polymerase binds to the operator.
D lactose is present and it binds to RNA polymerase.

Answer: lactose is present and it binds to the », repressor.
119 Which of the following are the functions of RNA?
A It is a constituent component of ribosomes
B It carries amino acids to ribosomes
C It is a carrier of genetic information from DNA to ribosomes synthesising polypeptides.
D All of the above.

Answer: All of the above.
120 In the lac operon of E.coli, the i gene codes for
A inducer
B repressor
C lactase
D β-galactosidase

Answer: repressor
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