Chapter 15: Genes And How They Work

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Questions and Answers
  • 1. 

    The connection that exists between genes and hereditary traits requires the deciphering of the information encoded in genes into

    • A.

      Amino acids.

    • B.

      Nucleotides.

    • C.

      Proteins.

    • D.

      Histone molecules.

    • E.

      Complementary bases.

    Correct Answer
    C. Proteins.
    Explanation
    Genes contain the instructions for making proteins, which are the building blocks of cells and perform various functions in the body. The process of gene expression involves the decoding of the information encoded in genes into proteins. This process begins with the transcription of DNA into messenger RNA (mRNA), followed by translation of mRNA into a sequence of amino acids, which then fold into functional proteins. Therefore, the connection between genes and hereditary traits is established through the production of proteins.

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  • 2. 

    Both DNA and RNA are made up of building blocks known as

    • A.

      Nucleotides.

    • B.

      Complementary base pairs.

    • C.

      Amino acids.

    • D.

      Genes.

    Correct Answer
    A. Nucleotides.
    Explanation
    Both DNA and RNA are composed of nucleotides, which are the building blocks of these molecules. Nucleotides consist of a sugar molecule, a phosphate group, and a nitrogenous base. These nitrogenous bases can be adenine (A), thymine (T), cytosine (C), and guanine (G) in DNA, or adenine (A), uracil (U), cytosine (C), and guanine (G) in RNA. The sequence of these nucleotides in DNA and RNA determines the genetic information and plays a crucial role in various biological processes. Therefore, nucleotides are the correct answer to this question.

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  • 3. 

    The "one gene-one enzyme" hypothesis was proposed by

    • A.

      Watson and Crick.

    • B.

      Griffith.

    • C.

      Garrod.

    • D.

      Franklin.

    • E.

      Beadle and Tatum.

    Correct Answer
    E. Beadle and Tatum.
    Explanation
    The "one gene-one enzyme" hypothesis states that each gene is responsible for the production of a single enzyme. Beadle and Tatum, through their experiments with the bread mold Neurospora crassa, provided evidence for this hypothesis. They exposed the mold to different mutagens and observed that specific mutations resulted in the inability to produce certain enzymes, leading to the conclusion that each gene controls the synthesis of a specific enzyme. This groundbreaking work earned Beadle and Tatum the Nobel Prize in Physiology or Medicine in 1958.

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  • 4. 

    DNA and RNA nucleotides are composed of five carbon sugars, phosphate, and nitrogen bases. How many total nitrogen bases are there for use in the two nucleic acids?

    • A.

      2

    • B.

      3

    • C.

      4

    • D.

      5

    Correct Answer
    D. 5
    Explanation
    DNA and RNA nucleotides are composed of five carbon sugars, phosphate, and nitrogen bases. Since both DNA and RNA contain four different nitrogen bases (adenine, guanine, cytosine, and thymine/uracil), the total number of nitrogen bases available for use in the two nucleic acids is 4 + 1 = 5.

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  • 5. 

    The polypeptide-making organelles residing in the cytoplasm are large protein aggregates to which RNA is associated. They are called

    • A.

      Ribosomes.

    • B.

      Golgi bodies.

    • C.

      Lysosomes.

    • D.

      The endoplasmic reticulum.

    • E.

      Mitochondria.

    Correct Answer
    A. Ribosomes.
    Explanation
    Ribosomes are the correct answer because they are the organelles responsible for protein synthesis in the cytoplasm. They consist of large protein aggregates to which RNA is associated, forming ribonucleoprotein particles. Ribosomes play a crucial role in translating the genetic information from mRNA into proteins. Golgi bodies, lysosomes, the endoplasmic reticulum, and mitochondria are all important organelles in the cell, but they are not directly involved in polypeptide synthesis like ribosomes.

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  • 6. 

    Amino acids are transported to the ribosome for use in building the polypeptide by

    • A.

      MRNA molecules.

    • B.

      TRNA molecules.

    • C.

      DNA polymerase molecules.

    • D.

      RRNA molecules.

    • E.

      DNA ligase molecules.

    Correct Answer
    B. TRNA molecules.
    Explanation
    tRNA molecules are responsible for transporting amino acids to the ribosome during protein synthesis. Each tRNA molecule carries a specific amino acid and has an anticodon that matches the codon on the mRNA molecule. This allows the tRNA molecule to bind to the mRNA and deliver the corresponding amino acid to the growing polypeptide chain. Therefore, tRNA molecules play a crucial role in the process of building a polypeptide by bringing the necessary amino acids to the ribosome.

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  • 7. 

    The process in which an RNA polymerase molecule assembles an mRNA molecule whose nucleotide sequence is complementary to the DNA sequence is called

    • A.

      Gene amplification.

    • B.

      Translation.

    • C.

      Transcription.

    • D.

      Polypeptide sequencing.

    • E.

      Complementary base pairing.

    Correct Answer
    C. Transcription.
    Explanation
    Transcription is the process in which an RNA polymerase molecule assembles an mRNA molecule whose nucleotide sequence is complementary to the DNA sequence. During transcription, the DNA strand acts as a template for the synthesis of mRNA, resulting in the formation of a complementary RNA molecule. This process occurs in the nucleus of eukaryotic cells and is essential for gene expression, as it allows the genetic information encoded in DNA to be transferred to RNA and ultimately to proteins. Gene amplification refers to the increase in the number of copies of a specific gene, translation is the process of protein synthesis, polypeptide sequencing is the determination of the amino acid sequence in a polypeptide chain, and complementary base pairing is the specific binding between nucleotide bases in DNA and RNA.

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  • 8. 

    Similar to the complementary purine-pyrimidine relationship observed in DNA, which of the following choices pairs with adenine in RNA?

    • A.

      Thymine

    • B.

      Cytosine

    • C.

      Guanine

    • D.

      Uracil

    Correct Answer
    D. Uracil
    Explanation
    In RNA, adenine pairs with uracil. This is because uracil is the pyrimidine base that complements adenine in RNA, just like thymine complements adenine in DNA. Adenine and uracil form a base pair through hydrogen bonding, contributing to the stability and structure of RNA molecules.

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  • 9. 

    The nucleotide sequence of a mRNA codon is composed of how many bases?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      16

    • E.

      64

    Correct Answer
    C. 3
    Explanation
    The nucleotide sequence of a mRNA codon is composed of three bases. Each codon consists of three nucleotides, which determine the specific amino acid that will be incorporated into a growing polypeptide chain during protein synthesis. Therefore, the correct answer is 3.

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  • 10. 

    The hereditary information in DNA is conveyed through the

    • A.

      Production of all three kinds of RNA molecules.

    • B.

      Production of a lipid bilayer.

    • C.

      Production of DNA copies.

    • D.

      Production of many proteins and polypeptides.

    • E.

      Production of all of the codons.

    Correct Answer
    D. Production of many proteins and polypeptides.
    Explanation
    The hereditary information in DNA is conveyed through the production of many proteins and polypeptides. DNA contains the instructions for making proteins, which are essential for the structure and function of cells. This process begins with the transcription of DNA into messenger RNA (mRNA), which carries the genetic code from the nucleus to the ribosomes in the cytoplasm. The mRNA is then translated into proteins by the ribosomes, using transfer RNA (tRNA) to match the codons on the mRNA with the appropriate amino acids. Therefore, the production of proteins and polypeptides is how the hereditary information in DNA is expressed and passed on.

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  • 11. 

    Protein synthesis takes place on

    • A.

      The plasma membrane.

    • B.

      The nucleus.

    • C.

      Ribosomes.

    • D.

      Lysosomes.

    • E.

      Microbodies.

    Correct Answer
    C. Ribosomes.
    Explanation
    Protein synthesis, the process of creating proteins, occurs on ribosomes. Ribosomes are small organelles found in the cytoplasm of cells and are responsible for translating the genetic information stored in DNA into proteins. They serve as the site where amino acids are linked together to form polypeptide chains, which then fold into functional proteins. The plasma membrane, nucleus, lysosomes, and microbodies do not play a direct role in protein synthesis, making ribosomes the correct answer.

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  • 12. 

    Ribosomes are complex arrangements of

    • A.

      RNA and DNA.

    • B.

      RNA and large proteins.

    • C.

      RNA and sugars.

    • D.

      DNA and proteins.

    • E.

      Nucleosomes and RNA.

    Correct Answer
    B. RNA and large proteins.
    Explanation
    Ribosomes are responsible for protein synthesis in cells. They are composed of two subunits, one large and one small. The large subunit contains both RNA and large proteins, while the small subunit contains mainly RNA. These subunits work together to read the genetic information encoded in RNA and assemble amino acids into a protein chain. Therefore, the correct answer is RNA and large proteins.

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  • 13. 

    The sites A, P, and E are progressively occupied by amino acids being assembled into a chain in protein synthesis. These sites are part of

    • A.

      Small ribosomal subunit.

    • B.

      Large ribosomal subunit.

    • C.

      MRNA.

    • D.

      TRNA.

    • E.

      DNA (the gene itself.)

    Correct Answer
    B. Large ribosomal subunit.
    Explanation
    The sites A, P, and E are involved in the process of protein synthesis, where amino acids are assembled into a chain. These sites are located within the ribosome, a complex molecular machine responsible for protein synthesis. The ribosome is composed of two subunits, the small and large ribosomal subunits. The large ribosomal subunit contains the A, P, and E sites, which play a crucial role in the binding and movement of tRNA molecules carrying amino acids during protein synthesis. Therefore, the correct answer is the large ribosomal subunit.

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  • 14. 

    Each amino acid has a specific tRNA molecule that can transport it to the site of protein synthesis. Therefore, in humans the number of different tRNA molecules would be

    • A.

      3.

    • B.

      20.

    • C.

      40.

    • D.

      80.

    • E.

      Thousands.

    Correct Answer
    B. 20.
    Explanation
    Each amino acid requires a specific tRNA molecule to transport it to the site of protein synthesis. Since there are 20 different amino acids used in protein synthesis, there must be 20 different tRNA molecules to transport them. Therefore, the correct answer is 20.

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  • 15. 

    In eukaryotic cells, mRNA is made as a copy of the DNA coding information in the

    • A.

      Cytoplasm.

    • B.

      Mitochondria.

    • C.

      ER.

    • D.

      Nucleus.

    • E.

      Plasma membrane.

    Correct Answer
    D. Nucleus.
    Explanation
    In eukaryotic cells, mRNA is made as a copy of the DNA coding information in the nucleus. This is because the nucleus is the organelle that contains the DNA, which serves as the template for mRNA synthesis. The process of transcription, where DNA is converted into mRNA, occurs in the nucleus. Once the mRNA is synthesized, it can then be transported out of the nucleus and into the cytoplasm, where it can be translated into proteins. Therefore, the correct answer is the nucleus.

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  • 16. 

    Gene expression includes which two of the following processes?

    • A.

      Transcription and replication

    • B.

      Replication and repression

    • C.

      Protein synthesis and replication

    • D.

      Mutation and cell division

    • E.

      Transcription and translation

    Correct Answer
    E. Transcription and translation
    Explanation
    Gene expression refers to the process by which the information encoded in a gene is used to synthesize a functional gene product, such as a protein. Transcription is the first step in gene expression, where the DNA sequence of a gene is transcribed into RNA. Translation is the subsequent step, where the RNA molecule is translated into a protein. Therefore, the correct answer is transcription and translation.

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  • 17. 

    The enzyme that initiates transcription is

    • A.

      RNA polymerase.

    • B.

      DNA polymerase.

    • C.

      Carbonic anhydrase.

    • D.

      ATP synthetase.

    • E.

      Transformation principle.

    Correct Answer
    A. RNA polymerase.
    Explanation
    RNA polymerase is the correct answer because it is the enzyme responsible for initiating transcription, which is the process of synthesizing RNA from a DNA template. RNA polymerase recognizes specific DNA sequences called promoters and binds to them, unwinding the DNA double helix and starting the synthesis of RNA. This enzyme plays a crucial role in gene expression and is essential for the production of all types of RNA molecules in cells. DNA polymerase, carbonic anhydrase, ATP synthetase, and transformation principle are not involved in transcription initiation, making them incorrect choices.

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  • 18. 

    Because nucleic acid sequence information is changed into amino acid sequence information, polypeptide synthesis is known as

    • A.

      Breaking the code.

    • B.

      Decoding.

    • C.

      Transcription.

    • D.

      Translocation.

    • E.

      Translation.

    Correct Answer
    D. Translocation.
  • 19. 

    The number of nucleotides required to specify an amino acid is

    • A.

      1.

    • B.

      2.

    • C.

      3.

    • D.

      4.

    • E.

      A variable number.

    Correct Answer
    C. 3.
    Explanation
    Each amino acid is specified by a sequence of three nucleotides called a codon. There are a total of 64 possible codons, which is more than enough to specify the 20 different amino acids found in proteins. Therefore, the number of nucleotides required to specify an amino acid is fixed at three.

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  • 20. 

    The genetic code operates on all the following principles except

    • A.

      All four of the nucleotide bases must be used.

    • B.

      Each combination of any three nucleotides can act as a codon.

    • C.

      The first nucleotide in every codon is always the same.

    • D.

      A particular codon always specifies the same amino acid.

    Correct Answer
    C. The first nucleotide in every codon is always the same.
    Explanation
    The genetic code operates on the principles that all four nucleotide bases must be used, each combination of any three nucleotides can act as a codon, and a particular codon always specifies the same amino acid. However, the first nucleotide in every codon is not always the same. This is because the genetic code is degenerate, meaning that multiple codons can code for the same amino acid. The first nucleotide in a codon can vary, while the second and third nucleotides are more specific in determining the amino acid.

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  • 21. 

    How many unique mRNA codons can be constructed from the four different RNA nucleotides?

    • A.

      4

    • B.

      8

    • C.

      16

    • D.

      32

    • E.

      64

    Correct Answer
    E. 64
    Explanation
    There are four different RNA nucleotides (A, U, G, C) that can be used to construct mRNA codons. Each codon is made up of three nucleotides. Since there are four options for each nucleotide, we can calculate the number of unique codons by multiplying these options together: 4 x 4 x 4 = 64. Therefore, 64 unique mRNA codons can be constructed from the four different RNA nucleotides.

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  • 22. 

    The 3-nucleotide sequence of an mRNA is called the

    • A.

      Codon.

    • B.

      Anticodon.

    • C.

      Amino acid.

    • D.

      Transcript.

    • E.

      Template.

    Correct Answer
    A. Codon.
    Explanation
    The 3-nucleotide sequence of an mRNA is called a codon. A codon is responsible for encoding a specific amino acid during protein synthesis. It acts as a template for the translation process, where the sequence of codons determines the order of amino acids in a protein. The anticodon, on the other hand, is found on tRNA and is complementary to the codon. Amino acids are the building blocks of proteins, but they are not directly referred to as the 3-nucleotide sequence of an mRNA. Transcript refers to the RNA molecule that is synthesized from DNA, and template refers to the DNA strand that is used as a guide for RNA synthesis.

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  • 23. 

    Besides the triplet nature of the genetic code, the other major piece of information that was provided by Crick and his coworkers is that

    • A.

      Each codon specified a different amino acid.

    • B.

      The code of all DNA molecules is the same.

    • C.

      The proteins made from the coded information are always the same.

    • D.

      The reading of the code occurs without any punctuation.

    • E.

      The genetic code is the same in all organisms with no exceptions.

    Correct Answer
    D. The reading of the code occurs without any punctuation.
    Explanation
    The correct answer is that the reading of the code occurs without any punctuation. This means that there are no breaks or pauses between the codons in the genetic code. The sequence of codons is read continuously to determine the sequence of amino acids in a protein. This discovery by Crick and his coworkers provided important information about how the genetic code is translated into proteins.

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  • 24. 

    The tRNA nucleotide sequence that lines up on the mRNA is

    • A.

      An intron.

    • B.

      An exon.

    • C.

      A release factor.

    • D.

      An initiation factor.

    • E.

      An anticodon.

    Correct Answer
    E. An anticodon.
    Explanation
    The tRNA nucleotide sequence that lines up on the mRNA is an anticodon. Anticodons are specific sequences of three nucleotides on tRNA molecules that complement the codons on mRNA during translation. This complementary base pairing ensures that the correct amino acid is added to the growing polypeptide chain. The anticodon on tRNA binds to the codon on mRNA through hydrogen bonding, allowing for accurate translation of the genetic code.

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  • 25. 

    Protein synthesis proceeds by the ribosome

    • A.

      Alternating between many chains.

    • B.

      Moving three nucleotides at a time on the mRNA.

    • C.

      Attaching amino acids in a random fashion.

    • D.

      Selecting the tRNA molecule that fits.

    • E.

      Attaching amino acids to the growing chain without charged tRNAs.

    Correct Answer
    B. Moving three nucleotides at a time on the mRNA.
    Explanation
    During protein synthesis, the ribosome moves along the mRNA molecule, reading it in groups of three nucleotides called codons. Each codon codes for a specific amino acid. By moving three nucleotides at a time, the ribosome can accurately select the correct tRNA molecule that carries the corresponding amino acid. This ensures that the amino acids are attached to the growing protein chain in the correct order, allowing for the synthesis of a functional protein.

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  • 26. 

    Specific amino acids are attached to tRNA molecules by

    • A.

      Activation enzymes.

    • B.

      Codons.

    • C.

      Anticodons.

    • D.

      Ribosomes.

    • E.

      Initiation factors.

    Correct Answer
    A. Activation enzymes.
    Explanation
    Amino acids are attached to tRNA molecules through a process called aminoacylation, which is catalyzed by activation enzymes. These enzymes recognize specific amino acids and attach them to their corresponding tRNA molecules, ensuring that the correct amino acid is incorporated into the growing polypeptide chain during protein synthesis. Codons and anticodons are involved in the recognition of mRNA and tRNA molecules during translation, while ribosomes and initiation factors play roles in the initiation and assembly of the translation machinery. However, it is the activation enzymes that directly attach the amino acids to tRNA molecules.

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  • 27. 

    The codons that serve as "stop" signals for the protein synthesis are called

    • A.

      Anticodons.

    • B.

      Stop codons.

    • C.

      Nonsense codons.

    • D.

      Amino acid codons.

    • E.

      TRNA codons.

    Correct Answer
    B. Stop codons.
    Explanation
    Stop codons are the codons that signal the termination of protein synthesis. They do not code for any amino acid and instead act as signals for the ribosome to stop translating the mRNA molecule. When a stop codon is encountered, the ribosome releases the newly synthesized protein and dissociates from the mRNA. Therefore, stop codons play a crucial role in determining the length and functionality of the protein being synthesized.

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  • 28. 

    The bond that forms between the newly added amino acid and the previous amino acid on the chain is called a

    • A.

      Hydrogen bond.

    • B.

      Hydrophobic bond.

    • C.

      Hydrophilic bond.

    • D.

      Phosphodiester bond.

    • E.

      Peptide bond.

    Correct Answer
    E. Peptide bond.
    Explanation
    A peptide bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid in a protein chain. This bond is formed through a condensation reaction, where a water molecule is eliminated. The resulting bond is a covalent bond, which is strong and stable. Therefore, the correct answer for this question is peptide bond.

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  • 29. 

    The initiation complex for protein synthesis contains all of the following except

    • A.

      A small ribosomal subunit.

    • B.

      MRNA.

    • C.

      TRNA with methionine.

    • D.

      A release factor.

    • E.

      An initiation factor.

    Correct Answer
    D. A release factor.
    Explanation
    The initiation complex for protein synthesis is responsible for starting the process of protein synthesis. It consists of several components, including a small ribosomal subunit, mRNA, tRNA with methionine, and initiation factors. The small ribosomal subunit binds to mRNA, while tRNA with methionine brings the first amino acid to the ribosome. Initiation factors help in the assembly of the complex. However, a release factor is not a part of the initiation complex. Release factors are involved in terminating protein synthesis by recognizing stop codons and releasing the newly synthesized protein from the ribosome.

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  • 30. 

    The different components of the protein synthesizing machinery include all of the following except

    • A.

      MRNA.

    • B.

      TRNA.

    • C.

      Ribosomes.

    • D.

      Amino acids.

    • E.

      RNA polymerase.

    Correct Answer
    E. RNA polymerase.
    Explanation
    The different components of the protein synthesizing machinery include mRNA, tRNA, ribosomes, and amino acids. RNA polymerase is not directly involved in protein synthesis but is responsible for transcribing DNA into RNA molecules. Therefore, RNA polymerase is not considered a component of the protein synthesizing machinery.

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  • 31. 

    Eukaryotic mRNA molecules are occasionally interspersed with non-coding sequences that must be removed before protein synthesis. These are called

    • A.

      Anticodons.

    • B.

      Introns.

    • C.

      Exons.

    • D.

      Nucleosomes.

    • E.

      Chromomeres.

    Correct Answer
    B. Introns.
    Explanation
    Eukaryotic mRNA molecules contain non-coding sequences called introns, which need to be removed before protein synthesis can occur. Introns do not code for proteins and are interspersed within the coding sequences called exons. The process of removing introns and joining exons together is known as splicing. Anticodons are sequences found on tRNA molecules and are involved in the translation of mRNA into proteins. Nucleosomes are structures formed by DNA and proteins, while chromomeres are condensed regions of chromosomes.

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  • 32. 

    The location of protein synthesis in eukaryotic cells is the

    • A.

      Nucleus.

    • B.

      Cytoplasm.

    • C.

      Plasma membrane.

    • D.

      Golgi apparatus.

    • E.

      Vacuole.

    Correct Answer
    B. Cytoplasm.
    Explanation
    In eukaryotic cells, protein synthesis occurs in the cytoplasm. This is where the ribosomes, the cellular structures responsible for protein synthesis, are located. The cytoplasm is the fluid-filled region within the cell, outside of the nucleus. The nucleus contains the cell's DNA, which provides the instructions for protein synthesis, but the actual process of synthesizing proteins takes place in the cytoplasm. Therefore, the correct answer is cytoplasm.

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  • 33. 

    In eukaryotes, mRNA processing involves all of the following events except

    • A.

      Elongation of the transcript.

    • B.

      Addition of a 5' cap.

    • C.

      Addition of a poly A to the 3' end.

    • D.

      Pre-mRNA splicing.

    • E.

      Association with the spliceosome.

    Correct Answer
    A. Elongation of the transcript.
    Explanation
    mRNA processing is a crucial step in eukaryotes where the primary transcript undergoes several modifications before it can be translated into a protein. These modifications include the addition of a 5' cap, which helps in mRNA stability and recognition by the ribosome, and the addition of a poly A tail at the 3' end, which also aids in stability and transport of the mRNA. Pre-mRNA splicing involves the removal of introns and joining of exons, resulting in a mature mRNA molecule. Association with the spliceosome is necessary for this splicing process. However, elongation of the transcript refers to the process of RNA polymerase adding nucleotides during transcription, which occurs before mRNA processing and is not a part of the processing itself.

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  • 34. 

    In eukaryotes, the empty RNA molecules exit the ribosome from the

    • A.

      E site.

    • B.

      P site.

    • C.

      A site.

    • D.

      Active site.

    • E.

      Allosteric site.

    Correct Answer
    A. E site.
    Explanation
    In eukaryotes, the empty RNA molecules exit the ribosome from the E site. The E site, also known as the exit site, is the location within the ribosome where the tRNA that has released its amino acid is situated before it exits the ribosome. This site allows for the efficient release of the tRNA molecule and helps in the recycling of the ribosome for the next round of protein synthesis.

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  • 35. 

    The Central Dogma of biology is stated as

    • A.

      Proteins --> RNA --> DNA.

    • B.

      RNA --> DNA --> proteins.

    • C.

      DNA --> proteins --> RNA.

    • D.

      DNA --> RNA --> proteins.

    Correct Answer
    D. DNA --> RNA --> proteins.
    Explanation
    The Central Dogma of biology describes the flow of genetic information in cells. It states that DNA is transcribed into RNA, which is then translated into proteins. This process occurs in all living organisms and is essential for the synthesis of proteins, which are the building blocks of cells and carry out various functions in the body. Therefore, the correct answer is DNA --> RNA --> proteins.

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  • 36. 

    The transfer of information from DNA to mRNA is referred to as

    • A.

      Transcription.

    • B.

      Translation.

    • C.

      Transformation.

    • D.

      Transference.

    • E.

      Translocation.

    Correct Answer
    A. Transcription.
    Explanation
    The transfer of information from DNA to mRNA is known as transcription. During transcription, the DNA molecule is used as a template to synthesize an mRNA molecule. This process occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells. It involves the enzyme RNA polymerase binding to the DNA and synthesizing a complementary mRNA strand. This mRNA molecule carries the genetic code from the DNA to the ribosomes, where it is translated into a protein during the process of translation.

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  • 37. 

    If the sequence of bases in a section of DNA is ATCGCTCC, what is the corresponding sequence of bases in mRNA?

    • A.

      ATCCGATT

    • B.

      TAGGCUGG

    • C.

      UAGCGAGG

    • D.

      TATCGGCC

    • E.

      AUCCGAUU

    Correct Answer
    C. UAGCGAGG
    Explanation
    The corresponding sequence of bases in mRNA is UAGCGAGG. In DNA, the bases are represented by A, T, C, and G. In mRNA, the base thymine (T) is replaced by uracil (U). Therefore, the sequence ATCGCTCC in DNA becomes UAGCGAGG in mRNA.

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  • 38. 

    If the DNA triplet code were ATG CGT, the tRNA anticodons would be

    • A.

      AUG CGU.

    • B.

      ATG CGT.

    • C.

      UAC GCA.

    • D.

      UAG CGU.

    Correct Answer
    C. UAC GCA.
    Explanation
    The DNA triplet code ATG CGT corresponds to the mRNA codons AUG CGU. Since tRNA anticodons are complementary to mRNA codons, the anticodons would be UAC GCA.

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  • 39. 

    Humans and a bacterium make human insulin. How is this possible?

    • A.

      The human insulin gene appears naturally in the bacteria.

    • B.

      The human insulin gene is a mutated form of a bacterial gene for bacterial insulin.

    • C.

      The human insulin gene was inserted into a bacterium's genome, and since the genetic code is nearly universal, the bacterium is able to produce human insulin.

    • D.

      The human insulin gene appears in bacteria that have been exposed to radiation treatments for diabetes.

    • E.

      The human insulin gene appears naturally in the bacteria that is an inhabitant of the GI tract of diabetic patients.

    Correct Answer
    C. The human insulin gene was inserted into a bacterium's genome, and since the genetic code is nearly universal, the bacterium is able to produce human insulin.
    Explanation
    The correct answer states that the human insulin gene was inserted into a bacterium's genome. This process is known as genetic engineering or recombinant DNA technology. By inserting the human insulin gene into the bacterium, it acquires the ability to produce human insulin. This is possible because the genetic code is nearly universal, meaning that the same DNA sequence can be translated into proteins in different organisms. Therefore, the bacterium can use the instructions from the human insulin gene to produce the human insulin protein.

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  • 40. 

    There are 45 different kinds tRNA (anticodons) available to serve as amino acid carriers, but there are 64 mRNA codons. Why aren't the tRNA anticodons and mRNA codons equal in number?

    • A.

      The reason is that the third base pair on the tRNA allows some flexibility (wobble); thus, some tRNA anticodons can recognize more than one mRNA codon.

    • B.

      The reason is that some tRNA anticodons can misread some of the mRNA codons, which creates a "wobble" in the tRNA anticodons that can be repaired by RNA repair enzymes.

    • C.

      The reason is that the third base pair on the mRNA codon allows some flexibility (wobble); thus, some tRNA anticodons can recognize more than one mRNA codon.

    • D.

      The reason is that the tRNA has the flexibility to choose which mRNA codons are necessary for building the polypeptide chain.

    Correct Answer
    A. The reason is that the third base pair on the tRNA allows some flexibility (wobble); thus, some tRNA anticodons can recognize more than one mRNA codon.
    Explanation
    The third base pair on the tRNA allows for some flexibility, known as "wobble," which means that some tRNA anticodons can recognize more than one mRNA codon. This flexibility is due to the fact that the third base pair on the tRNA can form non-standard base pairs with the corresponding base on the mRNA codon. This allows for a degree of redundancy in the genetic code, as multiple codons can code for the same amino acid.

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  • 41. 

    Eukaryotic organisms and prokaryotic organisms differ in how gene information is processed. Select the statement that best explains this difference.

    • A.

      Prokaryote genes are transcribed into mRNA, which is translated immediately. Eukaryote genes contain long sequences of nucleotides that do not code for amino acids and have to be removed from the primary transcript.

    • B.

      Prokaryote genes are transcribed directly into a polypeptide, while eukaryote genes have mRNA and tRNA involved in polypeptide assembly.

    • C.

      Prokaryote genes are translated before being transcribed into mRNA. Eukaryotic genes are transcribed into mRNA and then translated.

    • D.

      Prokaryote genes are edited of all introns before being transcribed into mRNA, while eukaryotic genes are edited after mRNA formation.

    Correct Answer
    A. Prokaryote genes are transcribed into mRNA, which is translated immediately. Eukaryote genes contain long sequences of nucleotides that do not code for amino acids and have to be removed from the primary transcript.
    Explanation
    Eukaryotic organisms and prokaryotic organisms differ in how gene information is processed. In prokaryotes, genes are transcribed into mRNA, which is then immediately translated into a polypeptide. On the other hand, eukaryotic genes contain long sequences of nucleotides that do not code for amino acids. These non-coding sequences, known as introns, need to be removed from the primary transcript before translation can occur. This process, called RNA splicing, ensures that only the coding regions, known as exons, are translated into a polypeptide. Therefore, the correct answer explains the difference between gene processing in prokaryotes and eukaryotes.

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  • 42. 

    Transcription is the first stage in the Central Dogma. Transcription is initiated by

    • A.

      DNA polymerase binding to the promoter.

    • B.

      RNA polymerase binding to the promoter.

    • C.

      MRNA polymerase binding to the promoter.

    • D.

      TRNA polymerase binding to the promoter.

    Correct Answer
    B. RNA polymerase binding to the promoter.
    Explanation
    Transcription is the process by which RNA is synthesized from a DNA template. It is initiated by RNA polymerase, not DNA polymerase, mRNA polymerase, or tRNA polymerase. RNA polymerase binds to the promoter region of the DNA, which signals the start of transcription.

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  • 43. 

    Initiation of transcription differs from initiation of DNA replication in several ways. One such difference is that transcription does not require

    • A.

      GTP or ATP.

    • B.

      Any enzymes.

    • C.

      A primer.

    • D.

      A DNA template strand.

    Correct Answer
    C. A primer.
    Explanation
    Initiation of transcription differs from initiation of DNA replication in several ways. One such difference is that transcription does not require a primer. In DNA replication, a primer is needed to provide a starting point for DNA polymerase to begin synthesizing a new DNA strand. However, in transcription, RNA polymerase can directly bind to the DNA template strand and initiate the synthesis of RNA without the need for a primer. This is because RNA polymerase does not require a pre-existing strand to start the synthesis process. Therefore, the correct answer is a primer.

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  • 44. 

    Transcription in prokaryotes is carried out by the enzyme _______, which unwinds and transcribes the gene.

    • A.

      DNA polymerase

    • B.

      DNA helicase

    • C.

      DNA gyrase

    • D.

      RNA ligase

    • E.

      RNA polymerase

    Correct Answer
    E. RNA polymerase
    Explanation
    RNA polymerase is the correct answer because it is the enzyme responsible for carrying out transcription in prokaryotes. Transcription is the process by which the genetic information in DNA is used to synthesize RNA molecules. RNA polymerase binds to the DNA template strand and unwinds the DNA double helix, allowing for the synthesis of a complementary RNA molecule. This RNA molecule will serve as a template for protein synthesis. DNA polymerase, DNA helicase, DNA gyrase, and RNA ligase are not involved in transcription, making them incorrect choices.

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  • 45. 

    Prokaryotes have one type of RNA polymerase. Eukaryotes have ____ types of RNA polymerase.

    • A.

      2

    • B.

      3

    • C.

      4

    • D.

      16

    • E.

      64

    Correct Answer
    B. 3
    Explanation
    Eukaryotes have three types of RNA polymerase. This is because eukaryotic cells have a more complex gene regulation system compared to prokaryotic cells. Each type of RNA polymerase in eukaryotes is responsible for transcribing different types of genes. RNA polymerase I transcribes genes that encode for ribosomal RNA, RNA polymerase II transcribes genes that encode for messenger RNA, and RNA polymerase III transcribes genes that encode for transfer RNA and other small non-coding RNAs. Therefore, eukaryotes require three types of RNA polymerase for the proper functioning of gene expression.

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  • 46. 

    Eukaryotic mRNA molecules are modified

    • A.

      In the cytoplasm.

    • B.

      At the ribosome.

    • C.

      In the nucleus.

    • D.

      At the Golgi complex.

    • E.

      At the initiation of transcription.

    Correct Answer
    C. In the nucleus.
    Explanation
    Eukaryotic mRNA molecules are modified in the nucleus. This is because eukaryotic cells have a distinct separation of nuclear and cytoplasmic compartments. mRNA molecules are transcribed from DNA in the nucleus and undergo several modifications, such as the addition of a 5' cap and a poly-A tail, as well as the removal of introns. These modifications help in mRNA stability, transport, and translation. Once the mRNA is fully processed, it is then exported from the nucleus to the cytoplasm, where it can be translated into proteins at the ribosome.

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  • 47. 

    The 3' Poly-A tail is attached to

    • A.

      The Poly-A polymerase enzyme.

    • B.

      The mRNA.

    • C.

      The tRNA.

    • D.

      The coding strand of the DNA molecule.

    • E.

      The template strand of the DNA molecule.

    Correct Answer
    B. The mRNA.
    Explanation
    The 3' Poly-A tail is attached to the mRNA. This is because the Poly-A tail is added to the 3' end of the mRNA molecule during post-transcriptional processing. The Poly-A tail consists of a string of adenine nucleotides and helps to stabilize the mRNA molecule, protect it from degradation, and facilitate its export from the nucleus to the cytoplasm. This tail is added by an enzyme called Poly-A polymerase, which specifically binds to the mRNA molecule and adds the adenine nucleotides one by one.

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  • 48. 

    RNA splicing in eukaryotic cell protein synthesis means

    • A.

      That the product of translation, called the primary transcript is cut and put back together to produce the mature mRNA transcript.

    • B.

      That the product of transcription, called the secondary transcript is cut and put back together to produce the mature tRNA transcript.

    • C.

      That the product of translation, called the primary transcript is cut and put back together to produce the mature tRNA transcript.

    • D.

      That the product of transcription, called the primary transcript is cut and put back together to produce the mature mRNA transcript.

    Correct Answer
    D. That the product of transcription, called the primary transcript is cut and put back together to produce the mature mRNA transcript.
    Explanation
    RNA splicing in eukaryotic cell protein synthesis refers to the process where the primary transcript, which is the product of transcription, is cut and reconnected to form the mature mRNA transcript. This process involves removing non-coding regions called introns and joining together the coding regions called exons. The mature mRNA transcript is then used as a template for translation to produce proteins.

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  • 49. 

    Noncoding DNA that interrupt the nucleotide sequence of a gene are called

    • A.

      Exons.

    • B.

      Introns.

    • C.

      Axons.

    • D.

      AnRNPs (snurps.)

    • E.

      Spliceosome.

    Correct Answer
    B. Introns.
    Explanation
    Introns are noncoding DNA sequences that interrupt the nucleotide sequence of a gene. They are removed during the process of gene expression through a process known as splicing. This allows the exons, which contain the coding regions of the gene, to be joined together to form the final mRNA molecule. Axons are part of nerve cells and have no relevance to this question. AnRNPs (snurps) and spliceosomes are involved in the splicing process, but they are not the correct answer to the question.

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  • 50. 

    Consider the following sequence: 5'AUGGCUACAGAUAGCUGGGGCUGAAAAAAAAAAAAAAAA3' Translated, the corresponding protein contains how many amino acids?

    • A.

      6

    • B.

      7

    • C.

      8

    • D.

      13

    Correct Answer
    B. 7
    Explanation
    The given sequence represents a messenger RNA (mRNA) sequence, where each group of three nucleotides (codon) codes for one amino acid in the corresponding protein. Counting the number of codons in the sequence, we find that there are 7 codons. Therefore, the corresponding protein contains 7 amino acids.

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