AP Biology Chapter 12 Quiz
Individual effort, one log-in/submission attempt, 60 minute timed assessment of concepts from Chapter 12.
- 1.
Griffith, in his 1928 experiments, demonstrated that bacterial strains could be genetically transformed. The evidence that DNA was the "transforming principle" responsible for this phenomenon came later. What was the key experiment that Avery, MacCleod, and McCarty performed to prove that DNA was responsible fore the genetic change from rough cells into smooth cells?
- 2.
Nitrogen and carbon are more abundant in proteins than sulfur. Why did Hershey and Chase use radioactive sulfur instead of nitrogen and carbon to label the protein portion of their bacteriophages in their experiments to determine whether parental protein or parental DNA is necessary for progeny phage production?
- 3.
What information about the structure of DNA was obtained from X-ray crystallographic data?
- 4.
The underlying structure of DNA is very simple, consisting of only four possible building blocks. How is ti possible for DNA to carry complex genetic information if its structure is so simple? (hint: looking for a numeric base to your answer).
- 5.
If 30% of an organism's DNA is thymine, then:
- A.
70% is purine.
- B.
20% is guanine.
- C.
30% is adenine.
- D.
70% is pyrimidine.
Correct Answer
C. 30% is adenine.Explanation
If 30% of an organism's DNA is thymine, it means that the remaining 70% must be divided among the other three nucleotides: adenine, guanine, and cytosine. Since guanine and cytosine are both purines, and the total percentage of purines is given as 70%, it follows that 20% must be guanine. Therefore, the remaining 50% must be divided between adenine and cytosine, with adenine making up 30% of the total DNA.Rate this question:
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- 6.
The double-helix model of DNA resembles a twisted ladder in which the rungs of the ladder are:
- A.
A purine paired with a pyrimidine.
- B.
A paired with G and C paired with T.
- C.
Sugar-phosphate paired with sugar-phosphate.
- D.
A 5 prime end paired with a 3 prime end.
Correct Answer
A. A purine paired with a pyrimidine.Explanation
In the double-helix model of DNA, the rungs of the ladder are made up of two nucleotide bases that are paired together. Purines (adenine and guanine) always pair with pyrimidines (thymine and cytosine) through hydrogen bonding. This pairing is essential for the stability and replication of DNA. Therefore, the correct answer is "a purine paired with a pyrimidine."Rate this question:
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- 7.
DNA replication is said to be semiconservative because:
- A.
One of the new molecules conserves both of the original DNA strands.
- B.
The new DNA molecule contains two new DNA strands.
- C.
Both of the new molecules contain one new strand and one old strand.
- D.
DNA polymerase conserves both of the old strands.
Correct Answer
C. Both of the new molecules contain one new strand and one old strand.Explanation
DNA replication is said to be semiconservative because both of the new molecules contain one new strand and one old strand. During replication, the DNA molecule unwinds and each original strand serves as a template for the synthesis of a new complementary strand. This results in two identical DNA molecules, each consisting of one original strand and one newly synthesized strand. This process ensures that genetic information is conserved and passed on to the next generation.Rate this question:
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- 8.
Select all the choice(s) that apply. In a DNA molecule:
- A.
The bases are covalently bonded to the sugars.
- B.
The sugars are covalently bonded to the phosphates.
- C.
The bases are hydrogen-bonded to one another.
- D.
The nucleotides are covalently bonded to one another.
Correct Answer(s)
A. The bases are covalently bonded to the sugars.
B. The sugars are covalently bonded to the pHospHates.
C. The bases are hydrogen-bonded to one another.
D. The nucleotides are covalently bonded to one another.Explanation
The correct answer choices explain the different types of bonds present in a DNA molecule. The bases are covalently bonded to the sugars, meaning that they share electrons between the atoms. The sugars are covalently bonded to the phosphates, forming a sugar-phosphate backbone. The bases are hydrogen-bonded to one another, creating the double helix structure of DNA. Lastly, the nucleotides, which make up the DNA molecule, are covalently bonded to one another through the sugar-phosphate backbone.Rate this question:
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- 9.
If the sequence of bases in one strand of DNA is 5' TAGCCT 3' then the sequence of bases in the other strand will be:
- A.
3' TCCGAT 5'
- B.
3' ATCGGA 5'
- C.
3' TAGCCT 5'
- D.
3' AACGGUA 5'
Correct Answer
B. 3' ATCGGA 5'Explanation
The sequence of bases in the other strand of DNA will be the complementary sequence to the given strand. In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). Therefore, the complementary sequence to 5' TAGCCT 3' will be 3' ATCGGA 5'.Rate this question:
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- 10.
Transformation occurs when:
- A.
DNA is transformed into RNA.
- B.
DNA is transformed into protein.
- C.
Bacteria cannot grow on penicillin.
- D.
Organisms receive foreign DNA and thereby acquire a new characteristic.
Correct Answer
D. Organisms receive foreign DNA and thereby acquire a new characteristic.Explanation
Transformation refers to the process in which organisms receive foreign DNA and incorporate it into their own genetic material, leading to the acquisition of new characteristics. This process is commonly observed in bacteria, where foreign DNA can be taken up from the environment and integrated into the bacterial genome, allowing the bacteria to express new traits. In contrast, the other options mentioned in the question, such as DNA being transformed into RNA or protein, or bacteria not growing on penicillin, do not accurately describe the concept of transformation.Rate this question:
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- 11.
Select the choice(s) that apply. Pyrimidines:
- A.
Are always paired with a purine.
- B.
Are thymine and cytosine.
- C.
Keep DNA from replicating too often.
- D.
Are adenine and guanine.
Correct Answer(s)
A. Are always paired with a purine.
B. Are thymine and cytosine.Explanation
Pyrimidines are always paired with a purine because in DNA, adenine always pairs with thymine and cytosine always pairs with guanine. This is known as complementary base pairing and is essential for DNA replication and transcription. Thymine and cytosine are examples of pyrimidines, while adenine and guanine are examples of purines.Rate this question:
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- 12.
Select the choice(s) that apply. Watson and Crick incorporated which of the following into their model of DNA structure?
- A.
Franklin's diffraction data.
- B.
Chargaff's rules.
- C.
Complementary base pairing.
- D.
Alternating sugar-phosphate backbone.
Correct Answer(s)
A. Franklin's diffraction data.
B. Chargaff's rules.
C. Complementary base pairing.
D. Alternating sugar-pHospHate backbone.Explanation
Watson and Crick incorporated Franklin's diffraction data into their model of DNA structure to understand the physical arrangement of the molecule. They also considered Chargaff's rules, which stated that the amount of adenine is equal to thymine and the amount of guanine is equal to cytosine in DNA. Additionally, they proposed the concept of complementary base pairing, where adenine pairs with thymine and guanine pairs with cytosine. Finally, they included the idea of an alternating sugar-phosphate backbone, where the sugar and phosphate molecules alternate in the DNA structure.Rate this question:
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- 13.
A nucleotide:
- A.
Is smaller than a base.
- B.
Is a subunit of a nucleic acid.
- C.
Has a lot of variable parts.
- D.
Has at least four phosphates.
- E.
Always joins with other nucleotides.
- F.
Always joins with other nucleotides.
Correct Answer
B. Is a subunit of a nucleic acid.Explanation
A nucleotide is a subunit of a nucleic acid. Nucleic acids, such as DNA and RNA, are made up of long chains of nucleotides. Each nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. These nucleotides join together through chemical bonds to form the backbone of the nucleic acid molecule. Therefore, the statement "a nucleotide is a subunit of a nucleic acid" accurately describes the role and structure of a nucleotide in biological systems.Rate this question:
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- 14.
During replication, separation of DNA strands requires:
- A.
Backbones to split.
- B.
Nucleotides to join together.
- C.
Hydrolysis and synthesis to occur.
- D.
Hydrogen bonds to unzip.
Correct Answer
D. Hydrogen bonds to unzip.Explanation
During DNA replication, the two strands of the double helix need to separate in order for new strands to be synthesized. This separation is achieved by breaking the hydrogen bonds that hold the complementary base pairs together. The hydrogen bonds are relatively weak, making them easier to break compared to the covalent bonds in the sugar-phosphate backbones. Therefore, the correct answer is that hydrogen bonds need to unzip in order for the DNA strands to separate during replication.Rate this question:
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- 15.
The central dogma of molecular biology:
- A.
States that DNA is a template for all RNA production.
- B.
States that DNA is a template only for DNA replication.
- C.
States that translation precedes transcription.
- D.
States that RNA is a template for DNA replication.
Correct Answer
A. States that DNA is a template for all RNA production.Explanation
The central dogma of molecular biology states that DNA is a template for all RNA production. This means that DNA serves as the blueprint for the synthesis of RNA molecules through a process called transcription. The RNA molecules can then be used as templates for the synthesis of proteins through a process called translation. This principle is fundamental to understanding how genetic information is stored and used in living organisms.Rate this question:
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- 16.
Transcription of a gene results in the production of:
- A.
An mRNA.
- B.
Proteins.
- C.
An rRNA
- D.
Ribozymes.
Correct Answer
A. An mRNA.Explanation
Transcription is the process by which a DNA sequence is copied into an mRNA molecule. This mRNA molecule carries the genetic information from the DNA to the ribosomes, where it serves as a template for protein synthesis. Therefore, the correct answer is "an mRNA" because transcription results in the production of mRNA.Rate this question:
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- 17.
Which of these does not characterize the process of transcription?
- A.
RNA is made with one strand of the DNA serving as a template.
- B.
In making RNA, the base uracil of RNA pairs with the base thymine of DNA.
- C.
The enzyme RNA polymerase synthesizes RNA.
- D.
RNA is made in the cytoplasm of eukaryotic cells.
Correct Answer
B. In making RNA, the base uracil of RNA pairs with the base thymine of DNA.Explanation
The process of transcription involves the synthesis of RNA using a DNA template. The enzyme RNA polymerase is responsible for catalyzing this process. RNA is made with one strand of the DNA serving as a template, and the base uracil of RNA pairs with the base adenine of DNA, not thymine. This is because RNA contains uracil instead of thymine. The statement "In making RNA, the base uracil of RNA pairs with the base thymine of DNA" is incorrect and does not characterize the process of transcription.Rate this question:
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- 18.
Because there are more codons than amino acids:
- A.
Some amino acids are specified by more than one codon.
- B.
Some codons specify more than one amino acid.
- C.
Some codons do not specify any amino acid.
- D.
Some amino acids do not have codons.
Correct Answer
A. Some amino acids are specified by more than one codon.Explanation
Some amino acids are specified by more than one codon because there are more possible combinations of three nucleotides (codons) than there are different amino acids. This allows for redundancy in the genetic code, meaning that multiple codons can code for the same amino acid. This redundancy provides a level of error tolerance and flexibility in protein synthesis.Rate this question:
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- 19.
If the sequence of bases in the coding strand of a DNA is TAGC then the sequence of bases in the mRNA will be:
- A.
AUCG
- B.
TAGC
- C.
UAGC
- D.
CGAU
Correct Answer
A. AUCGExplanation
The sequence of bases in the mRNA is complementary to the coding strand of DNA. In DNA, the base pairs are A-T and G-C. Therefore, the complementary sequence of TAGC in mRNA would be AUCG.Rate this question:
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- 20.
During protein synthesis an anticodon on tRNA pairs with:
- A.
DNA nucleotide bases.
- B.
RRNA nucleotide bases.
- C.
MRNA nucleotide bases.
- D.
TRNA nucleotide bases.
Correct Answer
C. MRNA nucleotide bases.Explanation
During protein synthesis, the anticodon on tRNA pairs with mRNA nucleotide bases. This is because tRNA carries specific amino acids to the ribosome, where mRNA acts as a template for protein synthesis. The anticodon on tRNA recognizes and binds to the complementary codon on mRNA, ensuring that the correct amino acid is added to the growing protein chain. This process is essential for the accurate translation of the genetic code into proteins.Rate this question:
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- 21.
In his work with pneumonia-causing bacteria and mice, Griffith found that:
- A.
The protein coat from pathogenic cells was able to transform nonpathogenic cells.
- B.
Heat-killed pathogenic cells caused pneumonia.
- C.
Some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
- D.
The polysaccharide coat of bacteria caused pneumonia.
- E.
Bacteriophages injected DNA into bacteria.
Correct Answer
C. Some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.Explanation
Griffith's work with pneumonia-causing bacteria and mice showed that when he mixed heat-killed pathogenic cells with live nonpathogenic cells, the nonpathogenic cells became pathogenic. This suggested that some substance from the pathogenic cells was transferred to the nonpathogenic cells, causing them to become pathogenic. This discovery laid the foundation for understanding bacterial transformation and the transfer of genetic material between cells.Rate this question:
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- 22.
Which one do you like?
- A.
Option 1
- B.
Option 2
- C.
Option 3
- D.
Option 4
Correct Answer
A. Option 1 -
- 23.
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
- A.
The origins of replication occur only at the 5' end.
- B.
Helicases and single-strand binding proteins work at the 5' end.
- C.
DNA polymerase can hoin new nucleotides only to the 3' end of a growing strand.
- D.
DNA ligase works only in the 3' to 5' direction.
- E.
Polymerase can work on only one strand at a time.
Correct Answer
C. DNA polymerase can hoin new nucleotides only to the 3' end of a growing strand.Explanation
The difference in how the leading and lagging strands of DNA molecules are synthesized is based on the fact that DNA polymerase can only add new nucleotides to the 3' end of a growing strand. The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized in short fragments called Okazaki fragments. This is because the DNA polymerase can only work on one strand at a time and has to continuously start and stop on the lagging strand to synthesize the fragments. The other options provided in the question are not relevant to the difference in synthesis of the leading and lagging strands.Rate this question:
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- 24.
In analyzing the number of different bases in a DNA sample which result would be consistent with the base-pairing rules?
- A.
A = G
- B.
A + G = C + T
- C.
A + T = G + T
- D.
A = C
- E.
G = T
Correct Answer
B. A + G = C + TExplanation
The base-pairing rules in DNA state that adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). Therefore, the result A + G = C + T is consistent with the base-pairing rules because it shows that the number of adenine bases (A) plus the number of guanine bases (G) is equal to the number of cytosine bases (C) plus the number of thymine bases (T).Rate this question:
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- 25.
The elongation of the leading strand during DNA synthesis:
- A.
Progresses away from the replication fork.
- B.
Occurs in the 3' to 5' direction.
- C.
Produces Okazaki fragments.
- D.
Depends on the action of DNA polymerase.
- E.
Does not require a template strand.
Correct Answer
D. Depends on the action of DNA polymerase.Explanation
The correct answer is "depends on the action of DNA polymerase." During DNA synthesis, the leading strand is synthesized continuously in the 5' to 3' direction, which is the same direction as the movement of the replication fork. DNA polymerase is the enzyme responsible for adding nucleotides to the growing strand, and it moves along the template strand in the 3' to 5' direction. Therefore, the elongation of the leading strand depends on the action of DNA polymerase.Rate this question:
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- 26.
In a nucleosome, the DNA is wrapped around:
- A.
Polymerase molecules.
- B.
Ribosomes.
- C.
Histones.
- D.
A thymine dimer.
- E.
Satellite DNA.
Correct Answer
C. Histones.Explanation
In a nucleosome, the DNA is wrapped around histones. Histones are proteins that help in organizing and compacting DNA within the nucleus of a cell. They act as spools around which the DNA is wound, forming a structure called a nucleosome. This packaging of DNA with histones allows for efficient storage and regulation of genetic material.Rate this question:
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- 27.
In eukaryotic cells transcription cannot begin until:
- A.
The two DNA strands have completely separated and exposed the promoter.
- B.
Several transcription factors have bound to the promoter.
- C.
The 5' caps are removed from the mRNA.
- D.
The DNA introns are removed from the template.
- E.
DNA nucleases have isolated the transcription unit.
Correct Answer
B. Several transcription factors have bound to the promoter.Explanation
Transcription is the process by which genetic information from DNA is copied into RNA. In eukaryotic cells, transcription cannot begin until several transcription factors have bound to the promoter. The promoter is a specific DNA sequence that signals the start of a gene, and transcription factors are proteins that bind to the promoter and help recruit the enzyme RNA polymerase, which is responsible for synthesizing RNA. These transcription factors are necessary to initiate the transcription process and ensure that it occurs at the correct time and place in the cell.Rate this question:
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- 28.
Which of the following is not true of a codon?
- A.
It consists of three nucleotides.
- B.
It may code for the same amino acid as another codon.
- C.
It never codes for more than one amino acid.
- D.
It extends from one end of a tRNA molecule.
- E.
It is the basic unit of the genetic code.
Correct Answer
D. It extends from one end of a tRNA molecule.Explanation
A codon is a sequence of three nucleotides that corresponds to a specific amino acid or a stop signal during protein synthesis. It is the basic unit of the genetic code, as it determines the order in which amino acids are assembled to form a protein. A codon can code for the same amino acid as another codon, as there is redundancy in the genetic code. However, a codon never codes for more than one amino acid. The statement that it extends from one end of a tRNA molecule is not true because a codon is part of the mRNA molecule, not the tRNA molecule.Rate this question:
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- 29.
The anticodon of a particular tRRNA molecule is:
- A.
Complementary to the corresponding mRNA codon.
- B.
Complementary to the corresponding triplet in rRNA.
- C.
The part of tRNA that bonds to a specific amino acid.
- D.
Changeable, depending on the amino acid that attaches to the tRNA.
- E.
Catalytic, making the tRNA a ribozyme.
Correct Answer
A. Complementary to the corresponding mRNA codon.Explanation
The anticodon of a tRRNA molecule is complementary to the corresponding mRNA codon. This means that the anticodon sequence on the tRNA molecule will bind to the codon sequence on the mRNA molecule during translation. The complementary base pairing between the anticodon and codon ensures that the correct amino acid is added to the growing polypeptide chain. This process is essential for the accurate synthesis of proteins in the cell.Rate this question:
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- 30.
Which of the following is not true of RNA processing?
- A.
Exons are cut out before mRNA leaves the nucleus.
- B.
Nucleotides may be added at both ends of the RNA.
- C.
Ribozymes may function in RNA splicing.
- D.
RNA splicing can be catalyzed by spliceosomes.
- E.
A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.
Correct Answer
A. Exons are cut out before mRNA leaves the nucleus.Explanation
RNA processing involves several steps, including the removal of introns and the addition of a 5' cap and a poly-A tail. Exons, which are the coding regions of the gene, are not cut out before mRNA leaves the nucleus. Instead, introns are removed through a process called splicing, which is catalyzed by spliceosomes or ribozymes. The final mRNA molecule that leaves the nucleus is a shorter, processed version of the primary transcript, which is often much longer due to the presence of introns. Therefore, the statement that exons are cut out before mRNA leaves the nucleus is not true.Rate this question:
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- 31.
Which of the following mutations would be most likely to have a harmful effect on an organism?
- A.
A nucleotide-pair substitution.
- B.
A deletion of three nucleotides near the middle of a gene.
- C.
A single nucleotide deletion in the middle of an intron.
- D.
A single nucleotide deletion near the end of the coding sequence.
- E.
A single nucleotide insertion downstream of, and close to, the start of the coding sequence.
Correct Answer
E. A single nucleotide insertion downstream of, and close to, the start of the coding sequence.Explanation
A single nucleotide insertion downstream of, and close to, the start of the coding sequence would be most likely to have a harmful effect on an organism. This is because it could potentially disrupt the reading frame of the gene, leading to a frameshift mutation. Frameshift mutations can alter the entire sequence of amino acids that are produced during translation, resulting in a nonfunctional or partially functional protein.Rate this question:
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- 32.
All of the following are considered post-transcriptional modification that occur in the nucleus except:
- A.
5 5' capping with methylated guanines.
- B.
The addition of a 3' poly-adenine tail.
- C.
The excision of introns from mRNA via spliceosome formation.
- D.
MRNA attachment to polyribosomes.
Correct Answer
D. MRNA attachment to polyribosomes.Explanation
Post-transcriptional modifications refer to the changes that occur to the mRNA molecule after it has been transcribed from DNA. These modifications include 5' capping with methylated guanines, the addition of a 3' poly-adenine tail, and the excision of introns from mRNA via spliceosome formation. These modifications take place in the nucleus. However, mRNA attachment to polyribosomes, which is the process of mRNA binding to ribosomes for translation into protein, occurs in the cytoplasm, not in the nucleus.Rate this question:
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- 33.
An operon in a bacterial genome is composed of:
- A.
Several structural genes that express proteins with similar function.
- B.
One or more structural genes, a promoter, an operator, and a terminator.
- C.
Incorporated DNA from plasmids.
- D.
Viral DNA from infection and reverse transription.
Correct Answer
B. One or more structural genes, a promoter, an operator, and a terminator.Explanation
An operon in a bacterial genome is composed of one or more structural genes, a promoter, an operator, and a terminator. This is because an operon is a functional unit of DNA that consists of a cluster of genes that are transcribed together and regulated as a single unit. The structural genes within the operon encode proteins with similar functions. The promoter is a DNA sequence where RNA polymerase binds to initiate transcription. The operator is a DNA sequence where a repressor protein can bind to block transcription. The terminator is a DNA sequence that signals the end of transcription.Rate this question:
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- 34.
Which of the following types of mutation involves only one base pair?
- A.
Inversion
- B.
Deletion
- C.
Addition
- D.
Substitution
Correct Answer
D. SubstitutionExplanation
Substitution is the correct answer because it involves the replacement of a single base pair with another base pair. This type of mutation can result in a change in the DNA sequence and potentially lead to the production of a different protein. In contrast, inversion, deletion, and addition mutations involve the alteration of multiple base pairs, either by rearranging their order or by adding or removing them.Rate this question:
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- 35.
What type of bonds join one strand of DNA to anothe rstrand of DNA forming a double helix?
- A.
Ionic bonds
- B.
Hydrogen bonds
- C.
Polar covalent bonds
- D.
Hydrophobic interactions
Correct Answer
B. Hydrogen bondsExplanation
Hydrogen bonds join one strand of DNA to another strand of DNA, forming a double helix. Hydrogen bonds are weak chemical bonds that occur between a hydrogen atom and an electronegative atom, such as oxygen or nitrogen. In the case of DNA, hydrogen bonds form between the nitrogenous bases of the two DNA strands. These hydrogen bonds provide stability to the DNA structure and allow for the separation and replication of the strands during DNA replication and transcription.Rate this question:
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- 36.
In gel electrophoresis, DNA fragments migrate toward the electrode that is:
- A.
Smaller.
- B.
Negative.
- C.
Positive.
- D.
Isoelectrically neutral.
Correct Answer
C. Positive.Explanation
In gel electrophoresis, DNA fragments migrate toward the positive electrode. This is because DNA is negatively charged due to the phosphate groups in its backbone. When an electric current is applied, the negatively charged DNA fragments are attracted to the positive electrode and move towards it. Therefore, the correct answer is positive.Rate this question:
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