DNA Repair And Mutation

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  • 1/21 Questions

    A mutation that affects only a single nucleotide is called

    • A regional mutation
    • A site mutation
    • A point mutation
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About This Quiz

Explore the fundamentals of DNA structure, replication, and protein synthesis in this DNA Repair and Mutation quiz. Assess your understanding of genetic material flow, DNA polymerase function, and bacterial chromosome shapes. Essential for learners in genetics and molecular biology.

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  • 2. 

    The bases of one strand of DNA match-up with the bases of the second strand according to base pairing rules, therefore, the two strands are said to be

    • Oppositely charged

    • Identical

    • Complementary

    Correct Answer
    A. Complementary
    Explanation
    The bases of one strand of DNA match-up with the bases of the second strand according to base pairing rules. This means that adenine pairs with thymine, and guanine pairs with cytosine. This complementary base pairing allows the two strands to fit together like puzzle pieces, creating a double helix structure. Therefore, the correct answer is complementary.

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  • 3. 

    The final step in gene expression is protein synthesis, or

    • Translation

    • Transcription

    • Replication

    Correct Answer
    A. Translation
    Explanation
    Translation is the final step in gene expression where the information encoded in mRNA is used to synthesize a specific protein. During translation, the ribosome reads the mRNA sequence and assembles amino acids in the correct order to form a polypeptide chain. This process occurs in the cytoplasm of the cell and is essential for the production of functional proteins that carry out various cellular functions. Transcription, on the other hand, is the process of synthesizing mRNA from DNA, while replication is the process of copying DNA. Therefore, translation is the correct answer as it accurately describes the final step in gene expression.

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  • 4. 

    A mutagen is

    • A chemical or physical agent that induces mutations

    • An enzyme that repairs mutations

    • A molecule which stabilizes DNA thus prevents mutations from occurring

    Correct Answer
    A. A chemical or physical agent that induces mutations
    Explanation
    A mutagen is a chemical or physical agent that induces mutations. Mutations are changes in the DNA sequence, and mutagens can cause these changes to occur. This can happen through various mechanisms, such as altering the DNA structure or interfering with the DNA replication process. Mutagens can be found in various forms, including chemicals, radiation, and certain types of viruses. Their ability to induce mutations is what distinguishes them as mutagens.

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  • 5. 

    The enzyme that catalyzes the synthesis of DNA is called

    • Helicase

    • DNA gyrase

    • DNA polymerase

    Correct Answer
    A. DNA polymerase
    Explanation
    DNA polymerase is the correct answer because it is the enzyme responsible for catalyzing the synthesis of DNA. DNA polymerase adds nucleotides to the growing DNA strand, using a template strand as a guide. It plays a crucial role in DNA replication, as it ensures the accurate and faithful copying of the genetic information during cell division. Helicase is involved in unwinding the DNA double helix, while DNA gyrase helps in relieving the torsional strain that builds up ahead of the replication fork. However, neither of these enzymes directly catalyzes the synthesis of DNA.

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  • 6. 

    The flow of genetic material in microbial cells usually proceeds from

    • Proteins through RNA to DNA

    • RNA through DNA to proteins

    • DNA through RNA to proteins

    Correct Answer
    A. DNA through RNA to proteins
    Explanation
    In microbial cells, the flow of genetic material typically starts with DNA, which contains the genetic instructions. This DNA is transcribed into RNA, a process known as transcription. The RNA then undergoes translation, where it is used as a template to synthesize proteins. Therefore, the correct answer is DNA through RNA to proteins.

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  • 7. 

    A new copy of a DNA molecule is precisely synthesized during a process called

    • Translation

    • Transcription

    • Replication

    Correct Answer
    A. Replication
    Explanation
    During replication, a new copy of a DNA molecule is accurately synthesized. This process occurs in the nucleus of a cell and involves the separation of the DNA double helix, followed by the assembly of complementary nucleotides to form two identical DNA molecules. Replication is essential for cell division and ensures that each daughter cell receives an exact copy of the genetic material. Transcription, on the other hand, involves the synthesis of RNA from a DNA template, while translation is the process of protein synthesis using the information encoded in mRNA.

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  • 8. 

    DNA polymerase catalyzes the synthesis of DNA in the

    • 3' to 5' direction

    • 5' to 3' direction

    • 5' to 7' direction

    • 7' to 5' direction

    Correct Answer
    A. 5' to 3' direction
    Explanation
    DNA polymerase catalyzes the synthesis of DNA in the 5' to 3' direction. This means that it adds new nucleotides to the 3' end of the growing DNA strand, using the 5' end as a template. The enzyme moves along the template strand in the 3' to 5' direction, reading the template in the opposite, or anti-parallel, direction. This allows for the accurate replication of the DNA molecule, as the new strand is synthesized in the same direction as the template strand.

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  • 9. 

    Most procaryotic proteins begin with this modified amino acid

    • N-formylmethionine

    • N-formylleucine

    • N-formylserine

    Correct Answer
    A. N-formylmethionine
    Explanation
    N-formylmethionine is the correct answer because it is the modified amino acid that is used as the starting amino acid in most procaryotic proteins. This modified form of methionine helps in initiating protein synthesis in bacteria. It contains a formyl group attached to the amino group of methionine, which is important for the recognition and binding of the initiator tRNA to the ribosome during translation. This formyl group is then removed from the amino acid after the initiation of protein synthesis.

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  • 10. 

    Mutations that arise without exposure to external agents are called

    • Induced mutations

    • Analogous mutations

    • Spontaneous mutations

    Correct Answer
    A. Spontaneous mutations
    Explanation
    Spontaneous mutations are mutations that occur naturally in an organism's DNA without any external factors or exposure to mutagens. These mutations can arise due to errors during DNA replication or spontaneous chemical changes in the DNA molecule. Unlike induced mutations, which are caused by external agents like radiation or chemicals, spontaneous mutations are random and unpredictable.

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  • 11. 
    A nonsense mutation results in - ProProfs

    A nonsense mutation results in

    • an abnormal elongation of a polypeptide

    • A premature termination of the synthesis of a polypeptide

    • A large deletion within the reading frame of a gene

    Correct Answer
    A. A premature termination of the synthesis of a polypeptide
    Explanation
    A nonsense mutation refers to a type of genetic mutation where there is a change in the DNA sequence that leads to the formation of a premature stop codon in the mRNA. This premature stop codon signals the termination of protein synthesis before the full polypeptide chain is completed. As a result, the synthesis of the polypeptide is prematurely terminated, leading to a truncated and nonfunctional protein. Therefore, the correct answer is "a premature termination of the synthesis of a polypeptide."

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  • 12. 

    The enzyme that repairs nicked DNA by forming a phosphodiester bond between adjacent nucleotides is

    • DNA ligase

    • DNA gyrase

    • Topoisomerases

    • Single-stranded binding proteins

    • Helicases

    Correct Answer
    A. DNA ligase
    Explanation
    DNA ligase is the correct answer because it is the enzyme responsible for repairing nicked DNA by forming a phosphodiester bond between adjacent nucleotides. This process is crucial for sealing the breaks in the DNA backbone and ensuring the integrity of the genetic material. DNA ligase plays a vital role in DNA replication, DNA repair, and recombination, making it essential for maintaining the stability and functionality of the genome.

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  • 13. 

    The chromosome of almost all bacteria is in the shape of

    • An open circle

    • A closed circle

    • A linear chromosome

    Correct Answer
    A. A closed circle
    Explanation
    The chromosome of almost all bacteria is in the shape of a closed circle. This means that the genetic material of bacteria is arranged in a circular structure, rather than a linear one like in eukaryotic organisms. The closed circle shape allows for efficient packaging of the genetic material within the bacterial cell. Additionally, the closed circle structure enables bacteria to replicate their DNA quickly and efficiently during cell division.

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  • 14. 

    The enzymes that unwind short stretches of DNA helix immediately ahead of a replication fork are

    • DNA gyrase

    • Topoisomerases

    • Helicases

    • Single-stranded binding proteins

    • DNA ligase

    Correct Answer
    A. Helicases
    Explanation
    Heliocases are enzymes that unwind short stretches of the DNA helix immediately ahead of a replication fork. They do this by breaking the hydrogen bonds between the DNA strands, allowing the replication machinery to access the DNA template for replication. DNA gyrase and topoisomerases are enzymes involved in relieving the torsional stress that builds up ahead of the replication fork. Single-stranded binding proteins stabilize the unwound DNA strands, preventing them from reannealing. DNA ligase, on the other hand, is responsible for joining the Okazaki fragments during DNA replication.

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  • 15. 

    The Shine-Dalgarno sequence is

    • The reading frame of a gene

    • A short sequence that acts as a ribosomal binding site

    • Another name for a stop codon

    Correct Answer
    A. A short sequence that acts as a ribosomal binding site
    Explanation
    The Shine-Dalgarno sequence is a short sequence that acts as a ribosomal binding site. This sequence is found in prokaryotic mRNA and is complementary to a sequence on the small subunit of the ribosome. It helps in positioning the ribosome correctly during translation initiation, allowing for efficient protein synthesis. This sequence is important for the recognition and binding of the mRNA to the ribosome, ensuring that the correct start codon is selected and translation begins at the appropriate site.

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  • 16. 

    DNA repair mechanisms are able to distinguish newly synthesized DNA strands from older strands because

    • New strands do not contain cytosine bases

    • Old strands are methylated while new strands are not

    • New strands are methylated while old strands are not

    Correct Answer
    A. Old strands are methylated while new strands are not
    Explanation
    DNA repair mechanisms are able to distinguish newly synthesized DNA strands from older strands because old strands are methylated while new strands are not. Methylation is a process where a methyl group is added to the DNA molecule, and it usually occurs on cytosine bases. Therefore, since the new strands do not contain cytosine bases, they do not undergo methylation. This difference in methylation patterns allows DNA repair mechanisms to recognize and distinguish between the older and newly synthesized DNA strands, enabling them to target and repair any damage or errors that may have occurred.

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  • 17. 

    The process by which thymine dimers are directly repaired with the help of visible light is called

    • Photosynthesis

    • Excision repair

    • Photoreactivation

    Correct Answer
    A. Photoreactivation
    Explanation
    Photoreactivation is the correct answer because it refers to the process by which thymine dimers, which are caused by UV radiation, are directly repaired with the help of visible light. This process involves the activation of a specific enzyme by visible light, which breaks the bonds between the thymine dimers and restores the DNA to its original state. Photosynthesis and excision repair are unrelated processes and do not involve the direct repair of thymine dimers with visible light.

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  • 18. 

    The actual process of protein synthesis takes place on ribosomes that serve as workbenches, with _____________ acting as the blueprint or template.

    Correct Answer
    mRNA
    Explanation
    During protein synthesis, ribosomes serve as the site where the actual process occurs. They use mRNA (messenger RNA) as a blueprint or template to guide the assembly of amino acids into a protein chain. mRNA carries the genetic information from DNA to the ribosomes, where it is read and translated into the specific sequence of amino acids that make up the protein. Therefore, mRNA plays a crucial role in protein synthesis by providing the instructions for the correct sequence of amino acids to be synthesized.

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  • 19. 
    The ability of the anticodon of tRNA to interact with multiple codons of mRNA is called - ProProfs

    The ability of the anticodon of tRNA to interact with multiple codons of mRNA is called

    • Wobble

    • Stagger

    • Promiscuity

    Correct Answer
    A. Wobble
    Explanation
    The ability of the anticodon of tRNA to interact with multiple codons of mRNA is called "wobble". This term refers to the flexibility of the base pairing rules between the third nucleotide of the codon and the first nucleotide of the anticodon. The wobble base pairing allows for some non-standard base pairing, such as G-U pairing, which expands the range of codons that can be recognized by a single tRNA molecule. This flexibility is crucial for efficient and accurate translation of the genetic code.

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  • 20. 

    Another name for the RNA polymerase recognition/binding site upstream of a gene is the

    Correct Answer
    Promoter
    Explanation
    The RNA polymerase recognition/binding site upstream of a gene is commonly referred to as the promoter. The promoter is a specific DNA sequence that signals the starting point for gene transcription. It provides a binding site for RNA polymerase, which initiates the transcription process by attaching to the promoter region. The promoter plays a crucial role in regulating gene expression and determining when and how much of a particular gene is transcribed.

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  • 21. 

    The ____________ is nontranslated sequence that is located between the transcription start site and the translation start site

    Correct Answer
    leader sequence
    Explanation
    The leader sequence is a nontranslated sequence that is located between the transcription start site and the translation start site. This sequence plays an important role in the regulation of gene expression and the initiation of translation. It contains specific signals that help in the recognition and binding of the ribosome to the mRNA molecule, ensuring the correct initiation of protein synthesis. Additionally, the leader sequence can also contain regulatory elements such as promoter regions and transcription factor binding sites, which further influence gene expression.

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Quiz Review Timeline (Updated): Mar 21, 2023 +

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

  • Current Version
  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jun 02, 2010
    Quiz Created by
    Clindo
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