Molecular Basis Of Inheritance

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| By Tanmay Shankar
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Tanmay Shankar
Community Contributor
Quizzes Created: 491 | Total Attempts: 1,797,843
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DNA Quizzes & Trivia

Time: 30 Minute


Questions and Answers
  • 1. 

    Select the incorrect option for genetic code?

    • A.

      It is nearly universal

    • B.

      It is degenerate

    • C.

      It is unambiguous

    • D.

      A codon in mRNA is read in a non contiguous fashion

    Correct Answer
    D. A codon in mRNA is read in a non contiguous fashion
    Explanation
    The genetic code is a set of rules that determines how the sequence of nucleotides in DNA or RNA is translated into the sequence of amino acids in a protein. The given statement, "A codon in mRNA is read in a non-contiguous fashion," is incorrect. In reality, a codon in mRNA is read in a contiguous fashion, meaning that the nucleotides are read consecutively in a specific order. Each codon consists of three nucleotides, and each codon codes for a specific amino acid or a stop signal. Therefore, this statement does not align with the characteristics of the genetic code.

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  • 2. 

    Removal of introns and joining the exons in a defined order in a transcription unit is called

    • A.

      Tailing

    • B.

      Transformation

    • C.

      Capping

    • D.

      Splicing

    Correct Answer
    D. Splicing
    Explanation
    Splicing refers to the process of removing introns, which are non-coding regions, from a transcription unit and joining together the exons, which are the coding regions, in a specific order. This process is crucial for generating a mature mRNA molecule that can be translated into a protein. Tailing, transformation, and capping are not related to this specific process and therefore are not the correct answers.

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  • 3. 

    Discontinuous synthesis of DNA occurs in one strand, because:

    • A.

      DNA molecule being synthesized is very long

    • B.

      DNA dependent DNA polymerase catalyses polymerization only in one direction (5' - 3')

    • C.

      It is a more efficient process

    • D.

      DNA ligase has to have a role

    Correct Answer
    B. DNA dependent DNA polymerase catalyses polymerization only in one direction (5' - 3')
    Explanation
    DNA dependent DNA polymerase catalyses polymerization only in one direction (5' - 3'). This means that it can only add nucleotides to the growing DNA strand in the 5' to 3' direction. As a result, the synthesis of the DNA molecule occurs discontinuously on one strand. The other strand, known as the lagging strand, is synthesized in short fragments called Okazaki fragments, which are later joined together by DNA ligase. This process is necessary to ensure accurate replication of the DNA molecule.

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  • 4. 

    Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA?

    • A.

      Rosalind Francklin

    • B.

      Maurice Wilkins

    • C.

      Erwin Chargaff

    • D.

      Meselson and Stahl

    Correct Answer
    D. Meselson and Stahl
    Explanation
    Meselson and Stahl did not contribute to the development of the double helix model for the structure of DNA. Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff were all instrumental in the discovery and understanding of DNA's structure. Franklin's X-ray crystallography work provided key insights, Wilkins' experiments further supported the double helix structure, and Chargaff's findings on base pairing rules were crucial in understanding the composition of DNA. However, Meselson and Stahl are known for their experiments on DNA replication and the semi-conservative nature of DNA, not for their contributions to the double helix model.

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  • 5. 

    Which of the following steps in transcription is catalysed by RNA polymerase?

    • A.

      Initiation

    • B.

      Elongation

    • C.

      Termination

    • D.

      All of the above

    Correct Answer
    B. Elongation
    Explanation
    RNA polymerase catalyzes the process of elongation during transcription. This is the step where RNA polymerase adds nucleotides to the growing RNA strand, using the DNA template as a guide. In this step, the RNA polymerase moves along the DNA template, unwinding the DNA helix and synthesizing the complementary RNA strand. This process continues until a termination signal is reached. Therefore, the correct answer is Elongation.

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  • 6. 

    Which of the following are the functions of RNA?

    • A.

      It is a carrier of genetic information from DNA to ribosomes synthesizing polypetides

    • B.

      It carries amino acids to ribosomes

    • C.

      It is a constituent component of ribosomes

    • D.

      All of the above

    Correct Answer
    C. It is a constituent component of ribosomes
    Explanation
    RNA is indeed a constituent component of ribosomes. Ribosomes are the cellular structures responsible for protein synthesis. They consist of ribosomal RNA (rRNA) and proteins. rRNA plays a crucial role in the functioning of ribosomes by helping to catalyze the assembly of amino acids into polypeptide chains. Therefore, the statement "It is a constituent component of ribosomes" is a valid function of RNA.

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  • 7. 

    In some viruses, DNA is synthesized by using RNA as template. Such a DNA is called:

    • A.

      A-DNA

    • B.

      B-DNA

    • C.

      CDNA

    • D.

      RDNA

    Correct Answer
    A. A-DNA
    Explanation
    A-DNA refers to the form of DNA that is synthesized by using RNA as a template. This type of DNA is commonly found in some viruses. It is important to note that A-DNA is different from the more common B-DNA, which is the standard double-stranded DNA structure found in most organisms. cDNA stands for complementary DNA and is synthesized from RNA using reverse transcriptase. rDNA refers to recombinant DNA, which is formed by combining DNA molecules from different sources.

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  • 8. 

    If Meselson and Stahl's experiment is continued for four generations is bacteria, the ratio of 15N/ 15N: 15N/14N: 14 N/14N containing DNA in the fourth generation would be:

    • A.

      1:1:0

    • B.

      1:4:0

    • C.

      0:1:3

    • D.

      0:1:7

    Correct Answer
    D. 0:1:7
    Explanation
    In Meselson and Stahl's experiment, they used a heavy isotope of nitrogen (15N) to label the DNA in the bacteria. They then transferred the labeled bacteria to a medium containing a lighter isotope of nitrogen (14N) and allowed them to replicate. After one round of replication, the DNA would consist of one strand labeled with 15N and one strand labeled with 14N, resulting in a ratio of 1:1. After two rounds of replication, the DNA would consist of two strands, one with 15N and one with 14N, resulting in a ratio of 1:2:1. After three rounds of replication, the DNA would consist of four strands, two with 15N and two with 14N, resulting in a ratio of 0:1:3. Therefore, after four generations, the DNA would consist of eight strands, one with 15N and seven with 14N, resulting in a ratio of 0:1:7.

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  • 9. 

    If the base sequence of a codon in mRNA is 5' AUG-3', the sequence of tRNA pairing with it must be:

    • A.

      5' UAC – 3'

    • B.

      5' - CAU - 3'

    • C.

      5' -AUG - 3'

    • D.

      5' - GUA - 3'

    Correct Answer
    B. 5' - CAU - 3'
    Explanation
    The given question is asking for the sequence of tRNA that pairs with the base sequence of the codon in mRNA, which is 5' AUG-3'. The tRNA molecule has an anticodon that pairs with the codon in mRNA through complementary base pairing. In this case, the anticodon would be 5' CAU-3' because it is complementary to the codon sequence 5' AUG-3'. Therefore, the correct answer is 5' - CAU - 3'.

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  • 10. 

    If the sequence of nitrogen base of the coding strand of DNA in a transcription unit is:

    • A.

      5' – A U G AA U G - 3'

    • B.

      5' – U A C U U A C - 3'

    • C.

      5' – C AU U C A U - 3'

    • D.

      5' – G U A A G U A - 3'

    Correct Answer
    A. 5' – A U G AA U G - 3'
    Explanation
    The given sequence is the coding strand of DNA in a transcription unit. During transcription, the DNA coding strand is used as a template to synthesize a complementary RNA molecule. The RNA molecule is synthesized in the 5' to 3' direction, so the sequence of the RNA molecule will be the same as the coding strand, except that thymine (T) is replaced with uracil (U). Therefore, the correct answer is 5' – A U G AA U G - 3'.

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  • 11. 

    The initiate translation, the mRNA first blinds to:

    • A.

      The smaller ribosomal sub-unit

    • B.

      The larger ribosomal sub-unit

    • C.

      The whole ribosome

    • D.

      No such specificity exists

    Correct Answer
    A. The smaller ribosomal sub-unit
    Explanation
    The correct answer is the smaller ribosomal sub-unit. During translation, mRNA first binds to the smaller ribosomal sub-unit. This binding allows for the initiation of protein synthesis and the assembly of the larger ribosomal sub-unit. The smaller sub-unit contains the mRNA binding site and plays a crucial role in the initiation of translation.

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  • 12. 

    In E.Coil, the lac Operon gets switched on when:

    • 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

    Correct Answer
    A. Lactose is present and it binds to the repressor
    Explanation
    The lac operon in E. coli is a regulatory system that controls the expression of genes involved in lactose metabolism. When lactose is present in the environment, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator. This allows RNA polymerase to bind to the operator and initiate transcription of the genes involved in lactose metabolism. Therefore, the lac operon gets switched on when lactose is present and it binds to the repressor.

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  • 13. 

    Which of the following sequence will be produced as a result of transcription of the DNA sequence –CGATTACAG

    • A.

      GCUAAUGUC

    • B.

      CGUAAUCUG

    • C.

      GCTAATGTC

    • D.

      GCUAATCTG

    Correct Answer
    A. GCUAAUGUC
    Explanation
    The given DNA sequence is CGATTACAG. During transcription, DNA is used as a template to synthesize an RNA molecule. In RNA, the base thymine (T) is replaced by uracil (U). The correct answer, GCUAAUGUC, is obtained by replacing T with U in the given DNA sequence.

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  • 14. 

    Sickle-cell haemoglobin has valine in place of glutamic acid at position 6 in the f3 polypeptide chain. Reason: Sickle-cell anaemia is expressed only in homozygous recessive state.

    • A.

      If both A and R are true R is the correct explanation of A

    • B.

      If both A and R are true but R is not the correct explanation of A

    • C.

      If A is true but R is false

    • D.

      If both A and R are false

    Correct Answer
    A. If both A and R are true R is the correct explanation of A
    Explanation
    The explanation provided is correct. Sickle-cell anaemia is indeed expressed only in the homozygous recessive state, meaning that an individual must inherit two copies of the sickle-cell gene (one from each parent) in order to develop the condition. The presence of valine in place of glutamic acid at position 6 in the f3 polypeptide chain is a characteristic of sickle-cell haemoglobin, and it is this abnormality that leads to the formation of sickle-shaped red blood cells and the symptoms of the disease. Therefore, the statement that "If both A and R are true, R is the correct explanation of A" is accurate in this case.

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  • 15. 

    DNA fingerprinting is very well known for its application in paternity testing is case of disputes. Reason: It employs the principle of polymorphism in DNA sequences as the polymorphisms are inheritable from parents to children

    • A.

      If both A and R are true R is the correct explanation of A

    • B.

      If both A and R are true but R is not the correct explanation of A

    • C.

      If A is true but R is false

    • D.

      If both A and R are false

    Correct Answer
    B. If both A and R are true but R is not the correct explanation of A
    Explanation
    The statement mentions that DNA fingerprinting is well known for its application in paternity testing. This implies that statement A is true. The reason given states that DNA fingerprinting employs the principle of polymorphism in DNA sequences, and these polymorphisms are inheritable from parents to children. While this reason is true, it does not directly explain why DNA fingerprinting is well known for its application in paternity testing. Therefore, although both A and R are true, R is not the correct explanation of A.

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Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Dec 22, 2013
    Quiz Created by
    Tanmay Shankar
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