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Molecular Basis of Inheritance Test 11

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Molecular Basis of Inheritance Test 11
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  • Question 1
    1 / -0

    Read the following text and answer the following questions on the basis of the same :

    DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components—a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and F. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.

    Which DNA form has the maximum number of base pairs per turn ?

    Solution

    Z DNA is the zigzag DNA that has the maximum number of base pairs per turn. It is a left-handed helix. There are 12 base pairs per turn, with a rise of 0.38 nm per base pair.

  • Question 2
    1 / -0

    The DNA replication is semi-conservative is proved by an experiment conducted by Meselson and Stahl in 1958. To perform their experiment they use heavy nitrogen (15N) in E. coli. The process of replication in living cells requires a set of enzymes. The main enzyme is DNA dependent DNA polymerase. The DNA-A dependent DNA polymerase catalyse polymerization only in one direction, that is 5→3'. In eukaryotes, the replication of DNA takes place at the S-phase of the cell cycle.

    Viruses grown in the presence of radioactive phosphorus contained radioactive ________ but not radioactive ________ .

    Solution

    DNA is the genetic material that came from the experiments of Hershey and Chase (1952). They worked with viruses that infect bacteria called bacteriophages. They worked to discover whether it was protein or DNA from the virus that entered the bacteria. They grew some viruses on a medium that contained radioactive phosphorus and some others on a medium that contained sulfur. Viruses grown in the presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not. Similarly, viruses grown on radioactive sulfur contained radioactive protein but not radioactive DNA because DNA does not contain sulphur.

  • Question 3
    1 / -0

    Read the following text and answer the following questions on the basis of the same :

    DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components—a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and F. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.

    Which among the following does not confer stability to the helical structure of DNA ?

    Solution

    N-glycosidic linkage in DNA, is the nitrogen carbon linkage between the nitrogen of purine or pyrimidine bases and the carbon of the sugar group. This bond does not provide stability.

  • Question 4
    1 / -0

    Read the following and answer the question given below:

    The lac operon consists of a regulation gene and three structural genes. The lactose acts as an inducer. In the presence of an Inducer such as lactose, the repressor is inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

    When the process of Lac operon is blocked by a repressor it represents :

    Solution

    The lac operon regulation can be in both negative and positive ways. It is a negative control system because expression is typically blocked by an active repressor (the lac repressor) that turns off transcription. And when CAP (catabolite gene activating protein) binds upstream of this operator region near the promoter and transcription increases, this is an example of a positive system.

  • Question 5
    1 / -0

    Read the following text and answer the following questions on the basis of the same :

    DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components—a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and F. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.

    Cytidine is a :

    Solution

    Cytosine (C) is a pyrimidine i.e., a nitrogenous base. A combination of a nitrogenous base (purine or pyrimidine) with a pentose sugar is known as nucleoside. Thus, the combination of cytosine with ribose sugar results in the formation of a nucleoside called cytidine.

  • Question 6
    1 / -0

    The DNA replication is semi-conservative is proved by an experiment conducted by Meselson and Stahl in 1958. To perform their experiment they use heavy nitrogen (15N) in E. coli. The process of replication in living cells requires a set of enzymes. The main enzyme is DNA dependent DNA polymerase. The DNA-A dependent DNA polymerase catalyse polymerization only in one direction, that is 5→3'. In eukaryotes, the replication of DNA takes place at the S-phase of the cell cycle.

    During DNA replication, the breaking of H-bonds is performed by :

    Solution

    DNA replication starts with unwinding of DNA duplexes which are held together by hydrogen bond. Helicases move along the double stranded DNA and separate the strands by breaking hydrogen bonds between base pairs.

  • Question 7
    1 / -0

    Read the following text and answer the following questions on the basis of the same :

    DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components—a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and F. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.

    Heaviest molecule of protoplasm is :

    Solution

    The heaviest molecule in the protoplasm is DNA. DNA is a compound of very high molecular weight (over one million), it has a giant molecule made of smaller molecules linked together, but its molecular weight is variable.

  • Question 8
    1 / -0

    Read the following and answer the question given below:

    The lac operon consists of a regulation gene and three structural genes. The lactose acts as an inducer. In the presence of an Inducer such as lactose, the repressor is inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

    Identify the correct sequence of the structural genes in the lac operon

    Solution

    The lac operon consists of 3 structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA.

  • Question 9
    1 / -0

    Read the following text and answer the following questions on the basis of the same :

    DNA, a long polymer of deoxyribonucleotide. Altmann and these substances to be acidic hence he named nucleic acid. The basic unit of DNA is a nucleotide which has three components—a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and F. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.

    Phosphoric acid is found in :

    Solution

    Phosphoric acid. H3PO4 provides the unit that holds the various segments of the nucleic acid chain to each other. It is present in all the three i;e: Nucleic acids; NAD and FAD; Phosphoprotein.

  • Question 10
    1 / -0

    The DNA replication is semi-conservative is proved by an experiment conducted by Meselson and Stahl in 1958. To perform their experiment they use heavy nitrogen (15N) in E. coli. The process of replication in living cells requires a set of enzymes. The main enzyme is DNA dependent DNA polymerase. The DNA-A dependent DNA polymerase catalyse polymerization only in one direction, that is 5→3'. In eukaryotes, the replication of DNA takes place at the S-phase of the cell cycle.

    How many types of DNA polymerases are associated with eukaryotic cells ?

    Solution

    5 types of DNA polymerases are associated with eukaryotic cell.

  • Question 11
    1 / -0

    Read the following and answer the question given below:

    The lac operon consists of a regulation gene and three structural genes. The lactose acts as an inducer. In the presence of an Inducer such as lactose, the repressor is inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

    Which of the following statements is true in reference to the lac operon process in E.coli?

    (i) Galactosidase is the only enzyme produced in large quantities when lac operon is turned on (ii) The messenger RNA in lac operon is a polycistronic mRNA

    Solution

    The messenger RNA produced by transcription carries information for the synthesis of all three proteins found in all three structural genes. Hence, it is a polycistronic messenger RNA.

  • Question 12
    1 / -0

    The DNA replication is semi-conservative is proved by an experiment conducted by Meselson and Stahl in 1958. To perform their experiment they use heavy nitrogen (15N) in E. coli. The process of replication in living cells requires a set of enzymes. The main enzyme is DNA dependent DNA polymerase. The DNA-A dependent DNA polymerase catalyse polymerization only in one direction, that is 5→3'. In eukaryotes, the replication of DNA takes place at the S-phase of the cell cycle.

    DNA replication is :

    Solution

    DNA replication is said to be semi-conservative because of the process of replication, where the resulting double helix is composed of both an old strand and a new strand. ... The two resulting double helices, which each contain one "old" strand and one "new" strand of DNA, are identical to the initial double helix.

    Due to this reason, replication occurs continuously on one strand and discontinuously on the other strand. This is known as the semi-discontinuous mode of replication. Every new DNA molecule that is formed has a new and an old strand of the DNA. Thus, during DNA replication, entirely new DNA copies are not generated.

  • Question 13
    1 / -0

    Read the following and answer the question given below:

    The lac operon consists of a regulation gene and three structural genes. The lactose acts as an inducer. In the presence of an Inducer such as lactose, the repressor is inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

    What provides a binding site to RNA polymerase?

    Solution

    Promoter helps in starting the process of transcription and provides a binding site to RNA polymerase.

  • Question 14
    1 / -0

    Directions : In the following questions a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as :

    Assertion (A) : Teminism is bidirectional flow of information.

    Reason (R) : It requires DNA dependent RNA polymerase enzymes.

    Solution

    Teminism is popularly known as reverse transcription, i.e., DNA can be synthesized by RNA.

  • Question 15
    1 / -0

    Read the following and answer the question given below:

    The lac operon consists of a regulation gene and three structural genes. The lactose acts as an inducer. In the presence of an Inducer such as lactose, the repressor is inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

    The lac operon of E. coli contains genes involved in lactose metabolism. It's expressed only when lactose is____________(1) and glucose is _________(2).

    Solution

    The lac operon of E. coli contains genes involved in lactose metabolism. It's expressed only when lactose is present and glucose is absent.

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