Molecular Genetics - DNA

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Biology16100
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Molecular Genetics - DNA - Quiz


Questions and Answers
  • 1. 

    Why was it important in the studies of Beadle and Tatum that Neurospora was haploid?

    • A.

      Because it is easier to grow haploid molds in the laboratory

    • B.

      Because haploid molds have simpler nutritional requirements that do diploid molds

    • C.

      Because a mutation that arises is not masked by a normal allele on a homologous chromosome.

    • D.

      Because haploid Neurospora will always mutate

    • E.

      Because diploid Neurospora will always mutate

    Correct Answer
    C. Because a mutation that arises is not masked by a normal allele on a homologous chromosome.
    Explanation
    The reason it was important for Beadle and Tatum to use haploid Neurospora in their studies is because a mutation that arises in a haploid organism is not masked by a normal allele on a homologous chromosome. In diploid organisms, a mutation on one chromosome can be masked by the presence of a normal allele on the other chromosome. By using haploid Neurospora, Beadle and Tatum were able to directly observe the effects of mutations on the organism's phenotype without interference from a normal allele.

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  • 2. 

    What conclusions did Beadle and Tatum reach with their studies of Neurospora?

    • A.

      Each mutant gene affected several enzymes

    • B.

      Each mutant gene affected a pair of enzymes

    • C.

      Each mutant gene affected only one enzyme

    • D.

      Mutant genes had no effect on the enzymes produced by the cells

    • E.

      None of the above are true

    Correct Answer
    C. Each mutant gene affected only one enzyme
    Explanation
    Beadle and Tatum concluded that each mutant gene affected only one enzyme based on their studies of Neurospora. This means that a specific gene mutation would result in a deficiency or alteration in the production of a single enzyme, rather than affecting multiple enzymes or having no effect on enzyme production.

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  • 3. 

    Bacteriophages used in Alfred Hershey’s and Martha Chase’s experiments showed that:

    • A.

      DNA was not injected into bacteria

    • B.

      Proteins were injected into bacteria

    • C.

      DNA remained on the outer coat of bacteria

    • D.

      Proteins were responsible for the production of new viruses within the bacteria

    • E.

      DNA was injected into bacteria

    Correct Answer
    E. DNA was injected into bacteria
    Explanation
    In Alfred Hershey's and Martha Chase's experiments, they used bacteriophages to determine whether DNA or proteins were injected into bacteria. The experiments showed that DNA was injected into bacteria. This conclusion was reached by using radioactive labeling to track the location of DNA and proteins in the bacteriophages. They found that the radioactive DNA was present inside the bacteria, while the radioactive proteins remained on the outer coat of the bacteria. This provided evidence that DNA, not proteins, was responsible for the production of new viruses within the bacteria.

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  • 4. 

    The two molecules that alternate to form the backbone of a polynucleotide chain are:

    • A.

      Adenine and thymine

    • B.

      Cytosine and guanine

    • C.

      Sugar and phosphate

    • D.

      Base and sugar

    • E.

      Base and phosphate

    Correct Answer
    A. Adenine and thymine
    Explanation
    The two molecules that alternate to form the backbone of a polynucleotide chain are adenine and thymine. These molecules are nitrogenous bases that pair together through hydrogen bonding. Adenine always pairs with thymine, and cytosine always pairs with guanine. The sugar and phosphate molecules make up the sides of the DNA ladder, while the bases form the rungs. Therefore, the correct answer is adenine and thymine.

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  • 5. 

    Why is DNA able to store large amounts of information?

    • A.

      It contains a large number of different nucleotides

    • B.

      Its nucleotides can be arranged in a large number of possible sequences

    • C.

      It is capable of assuming a wide variety of shapes

    • D.

      Both a and b are correct

    • E.

      Both a and c are correct

    Correct Answer
    C. It is capable of assuming a wide variety of shapes
    Explanation
    DNA is able to store large amounts of information because it is capable of assuming a wide variety of shapes. The structure of DNA allows it to form a double helix, with the nucleotide bases on each strand pairing up in a specific way. This allows for a large number of possible sequences, and therefore a large amount of information can be encoded in the DNA molecule. Additionally, the ability of DNA to form different shapes is important for its functions, such as DNA replication and gene expression.

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  • 6. 

    Two chains of DNA must run in                  direction(s) and must be                   if they are to bond with each other

    • A.

      The same; uncomplimentary

    • B.

      Opposite; uncomplimentary

    • C.

      Parallel; uncomplimentary

    • D.

      Parallel; complimentary

    • E.

      Antiparallel; complimentary

    Correct Answer
    E. Antiparallel; complimentary
    Explanation
    The two chains of DNA must run in an antiparallel direction and must be complimentary if they are to bond with each other. This means that one chain runs in the 5' to 3' direction, while the other runs in the 3' to 5' direction. Additionally, the bases on each chain must be complementary to each other (A with T, and G with C) in order to form hydrogen bonds and stabilize the DNA structure.

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  • 7. 

    Hydrogen bond(s) can form between guanine and                  while hydrogen bond(s) form between adenine and                  

    • A.

      Phosphate; sugar

    • B.

      Thymine; cytosine

    • C.

      Cytosine; thymine

    • D.

      Sugar; phosphate

    • E.

      Adenine; guanine

    Correct Answer
    C. Cytosine; thymine
    Explanation
    Hydrogen bonds can form between guanine and cytosine, while hydrogen bonds form between adenine and thymine. This is a fundamental concept in molecular biology known as base pairing. Guanine and cytosine have three hydrogen bonds between them, while adenine and thymine have two hydrogen bonds. These hydrogen bonds contribute to the stability and specificity of DNA double helix structure.

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  • 8. 

    The sugar that is in the backbone of DNA is called: 

    • A.

      Deltaglucose

    • B.

      Deoxyribose

    • C.

      Fructose

    • D.

      Ribose

    Correct Answer
    A. Deltaglucose
  • 9. 

    What is the true structure of DNA?

    • A.

      A double helix

    • B.

      A molecule

    • C.

      A strand

    • D.

      A stranded molecule

    • E.

      A triple helix

    Correct Answer
    A. A double helix
    Explanation
    The true structure of DNA is a double helix. This means that DNA consists of two strands that are twisted around each other in a spiral shape. The double helix structure of DNA was first discovered by James Watson and Francis Crick in 1953. It is composed of nucleotides, which are the building blocks of DNA, and the two strands are held together by hydrogen bonds between complementary base pairs. The double helix structure of DNA allows for the replication and transmission of genetic information.

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  • 10. 

    In addition to the standard organic elements of carbon, hydrogen and oxygen, nucleic acids also contain                

    • A.

      Phosphorus

    • B.

      Calcium

    • C.

      Nitrogen

    • D.

      Sulfur

    Correct Answer
    C. Nitrogen
    Explanation
    Nucleic acids, such as DNA and RNA, are composed of nucleotide units, which consist of a sugar molecule, a phosphate group, and a nitrogenous base. Nitrogen is an essential component of the nitrogenous bases found in nucleic acids, including adenine, guanine, cytosine, and thymine/uracil. These nitrogenous bases form the genetic code and are responsible for the information storage and transmission in living organisms. Therefore, it is correct to say that nucleic acids contain nitrogen.

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  • 11. 

    What's the name of the monomer that makes up a nucleic acid? 

    • A.

      Phospholipid

    • B.

      Nucleotide

    • C.

      Ribose

    • D.

      Deoxyribose

    Correct Answer
    B. Nucleotide
    Explanation
    A nucleotide is the monomer that makes up a nucleic acid. Nucleic acids, such as DNA and RNA, are composed of long chains of nucleotides. Each nucleotide consists of a phosphate group, a sugar molecule (either ribose or deoxyribose), and a nitrogenous base. The nucleotides join together through phosphodiester bonds to form the backbone of the nucleic acid molecule. Therefore, nucleotide is the correct answer as it is the building block of nucleic acids.

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  • 12. 

    Which of the following is not part of a nucleotide?

    • A.

      Nitrogen base

    • B.

      Monosaccharide sugar

    • C.

      Phosphate group

    • D.

      Oxygen base

    Correct Answer
    D. Oxygen base
    Explanation
    The correct answer is "oxygen base" because there is no such thing as an "oxygen base" in a nucleotide. A nucleotide is composed of three main components: a nitrogen base, a monosaccharide sugar, and a phosphate group. The nitrogen base is responsible for encoding genetic information, the monosaccharide sugar provides the backbone structure, and the phosphate group links the nucleotides together.

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  • 13. 

    Sugar bonds to                      to form the backbone of DNA

    • A.

      Carbonate

    • B.

      Phosphate

    • C.

      Oxalate

    • D.

      Sulfate

    Correct Answer
    B. Phosphate
    Explanation
    Phosphate bonds to form the backbone of DNA. The backbone of DNA is made up of a sugar-phosphate backbone, where the phosphate groups link the sugar molecules together. This backbone provides stability and structure to the DNA molecule. Carbonate, oxalate, and sulfate do not play a role in the formation of the DNA backbone.

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  • 14. 

    In DNA, adenine forms a complementary pair with what other nitrogen base?

    • A.

      Uracil

    • B.

      Cytosine

    • C.

      Thymine

    • D.

      Guanine

    Correct Answer
    C. Thymine
    Explanation
    Adenine forms a complementary pair with thymine in DNA. This is due to the specific hydrogen bonding patterns between the nitrogenous bases. Adenine and thymine are connected by two hydrogen bonds, creating a stable base pair. This complementary pairing is essential for DNA replication and the accurate transmission of genetic information.

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  • 15. 

    Guanine forms a complementary pair with what other nitrogen base?

    • A.

      Uracil

    • B.

      Cytosine

    • C.

      Thymine

    • D.

      Adenine

    Correct Answer
    B. Cytosine
    Explanation
    Guanine forms a complementary pair with cytosine. In DNA, guanine always pairs with cytosine through three hydrogen bonds, forming a stable base pair. This complementary pairing is essential for the structure and function of DNA, as it allows for accurate replication and transcription of genetic information.

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  • 16. 

    According to Chargaff's rule, the following proportion exists in DNA

    • A.

      C=G

    • B.

      C>T

    • C.

      C>G

    • D.

      C=T

    Correct Answer
    A. C=G
    Explanation
    Chargaff's rule states that in DNA, the amount of cytosine (C) is equal to the amount of guanine (G). This means that the proportion of C=G is maintained. The other proportions mentioned in the question (C>T and C=T) do not follow Chargaff's rule and are therefore incorrect.

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  • 17. 

    By convention, the sequence of bases in a nucleic acid is usually expressed in the                direction

    • A.

      3' to 1'

    • B.

      3' to 5'

    • C.

      1' to 3'

    • D.

      5' to 3'

    • E.

      Clockwise

    Correct Answer
    D. 5' to 3'
    Explanation
    The correct answer is 5' to 3'. In DNA and RNA, the sequence of bases is written from the 5' end to the 3' end. This convention is based on the structure of the nucleic acid molecule, where the 5' end has a phosphate group attached to the 5th carbon of the sugar molecule, and the 3' end has a hydroxyl group attached to the 3rd carbon of the sugar molecule. Therefore, when expressing the sequence of bases, it is written in the direction from the 5' end to the 3' end.

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  • 18. 

    In nucleic acids, the free hydroxyl group is attached to the                carbon of the sugar

    • A.

      5'

    • B.

      4'

    • C.

      3'

    • D.

      2'

    • E.

      1'

    Correct Answer
    C. 3'
    Explanation
    In nucleic acids, the free hydroxyl group is attached to the 3' carbon of the sugar. This is because nucleic acids are made up of nucleotides, which consist of a sugar molecule (deoxyribose in DNA and ribose in RNA) attached to a phosphate group and a nitrogenous base. The carbon atoms in the sugar molecule are numbered from 1' to 5', with the 3' carbon being the one that has the free hydroxyl group attached to it. This hydroxyl group is important for the formation of phosphodiester bonds between nucleotides, which are crucial for the structure and function of nucleic acids.

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  • 19. 

    In DNA, thymine always pairs with:

    • A.

      Adenine

    • B.

      Cytosine

    • C.

      Guanine

    • D.

      Thymine

    • E.

      Uracil

    Correct Answer
    A. Adenine
    Explanation
    In DNA, thymine always pairs with adenine. This is because of the complementary base pairing rule, where adenine forms two hydrogen bonds with thymine. This pairing is essential for the replication and transcription processes in DNA, as it ensures the accurate copying and reading of genetic information.

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  • 20. 

    In a nucleic acid, the bases are always attached to the                  carbon of the sugar

    • A.

      5'

    • B.

      4'

    • C.

      3'

    • D.

      2'

    • E.

      1'

    Correct Answer
    E. 1'
    Explanation
    In a nucleic acid, the bases are always attached to the 1' carbon of the sugar. This is because the sugar molecule in a nucleic acid has a carbon backbone, with each carbon numbered from 1 to 5. The base is attached to the 1' carbon, while the phosphate group is attached to the 5' carbon. This arrangement allows for the formation of a sugar-phosphate backbone, with the bases extending outwards, forming the rungs of the DNA ladder.

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  • 21. 

    In nucleic acids, the phosphate group is attached to the              carbon of the sugar

    • A.

      5'

    • B.

      4'

    • C.

      3'

    • D.

      2'

    • E.

      1'

    Correct Answer
    A. 5'
    Explanation
    In nucleic acids, the phosphate group is attached to the 5' carbon of the sugar. This is because the carbon atoms in the sugar molecule are numbered from 1' to 5', with the 5' carbon being the one closest to the phosphate group. The phosphate group forms a phosphodiester bond with the 3' carbon of the adjacent sugar molecule, creating a chain of nucleotides. This arrangement is important for the structure and function of nucleic acids, as it allows for the formation of the double helix in DNA and the synthesis of RNA.

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  • 22. 

    The two sides of the double helix structure are held together with hydrogen bonds

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The double helix structure of DNA is held together by hydrogen bonds. These bonds form between the nitrogenous bases of the two DNA strands. Specifically, adenine (A) pairs with thymine (T) through two hydrogen bonds, while guanine (G) pairs with cytosine (C) through three hydrogen bonds. These hydrogen bonds provide stability to the DNA molecule and allow for the separation and replication of the strands during DNA replication and transcription. Therefore, the statement is true.

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  • 23. 

    Base pairs in DNA are linked by what type of bonds?

    • A.

      Nitrogen

    • B.

      Oxygen

    • C.

      Hydrogen

    • D.

      Sulfate

    Correct Answer
    C. Hydrogen
    Explanation
    The correct answer is hydrogen because base pairs in DNA are linked together by hydrogen bonds. These bonds form between specific nitrogenous bases: adenine (A) pairs with thymine (T) through two hydrogen bonds, while guanine (G) pairs with cytosine (C) through three hydrogen bonds. These hydrogen bonds are relatively weak, allowing the DNA strands to separate during replication and transcription processes.

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  • 24. 

    Protein structure and function is determined by the amino acid sequence

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The statement that protein structure and function is determined by the amino acid sequence is true. Proteins are made up of long chains of amino acids, and the specific sequence of these amino acids determines the overall structure and function of the protein. Different amino acids have different properties, such as being hydrophobic or hydrophilic, and these properties influence how the protein folds and interacts with other molecules. Therefore, any changes in the amino acid sequence can have significant effects on the protein's structure and function.

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  • 25. 

    Genes code for proteins

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Genes are segments of DNA that contain the instructions for building proteins. Proteins are essential molecules that perform various functions in the body, such as enzymes, structural components, and signaling molecules. Therefore, it is correct to say that genes code for proteins.

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  • Current Version
  • May 22, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Mar 21, 2016
    Quiz Created by
    Biology16100
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