 Earlier work had shown that DNA is composed of building blocks called nucleotides consisting of a deoxyribose sugar, a phosphate group, and one of four nitrogen bases — adenine (A), thymine (T), guanine (G), and cytosine (C). Phosphates and sugars of adjacent nucleotides link to form a long polymer. Other key experiments showed that the ratios of A-to-T and G-to-C are constant in all living things. X-ray crystallography provided the final clue that the DNA molecule is a double helix, shaped like a twisted ladder. In 1953, the race to determine how these pieces fit together in a three-dimensional structure was won by James Watson and Francis Crick at the Cavendish Laboratory in Cambridge, England. They showed that alternating deoxyribose and phosphate molecules form the twisted uprights of the DNA ladder. The rungs of the ladder are formed by complementary pairs of nitrogen bases — A always paired with T and G always paired with C.
Which sugar is found in the back bone of DNA? Possible Answers:
Correct answer: Deoxyribose Explanation: DNA stands for "deoxyribonucleic acid." The backbone of DNA is comprised of alternating sugar and phosphate units, in which the sugar is deoxyribose. The backbone of RNA is also comprised of sugar and phosphate units, but uses the sugar ribose.
Which of the following might you find in the backbone of DNA? I. Phosphate group II. Hexose sugar III. Adenine Possible Answers:
Explanation: A DNA molecule has two primary structural domains: the DNA backbone and the DNA bases. Recall that all DNA molecules are made from nucleotides. One nucleotide of a DNA molecule consists of a phosphate group, a pentose (five-carbon) sugar called deoxyribose, and a nitrogenous base (adenine, thymine, guanine, cytosine). Several of these nucleotide monomers are joined together by phosphodiester bonds to create a DNA molecule. The backbone of a DNA molecule consists of the phosphate groups and the deoxyribose sugars, whereas the base region of the DNA molecule consists of the nitrogenous bases; therefore, the backbone of DNA is made up of phosphate groups and pentose sugars. Adenine is part of the base region of the molecule. DNA does not contain any hexose (six-carbon) sugars.
DNA splicing is the process of removing DNA from one organism and inserting it into a new organism's genome. Which of the following is required to cut DNA molecules in this process? Possible Answers:
Peptidase is needed to break the bonds between the phosphate group on the 5' carbon of one sugar and hydroxyl group on the 3' carbon of the adjacent sugar
Phosphodiesterase is needed to break the bonds between the phosphate group on the 5' carbon of one sugar and hydroxyl group on the 3' carbon of the adjacent sugar
Phosphodiesterase is needed to break the bonds between the phosphate group on the 3' carbon of one sugar and hydroxyl group on the 5' carbon of the adjacent sugar
Peptidase is needed to break the bonds between the phosphate group on the 3' carbon of one sugar and hydroxyl group on the 5' carbon of the adjacent sugar
Correct answer: Phosphodiesterase is needed to break the bonds between the phosphate group on the 5' carbon of one sugar and hydroxyl group on the 3' carbon of the adjacent sugar Explanation: A DNA molecule is made up of multiple nucleotides that are connected by phosphodiester bonds. A nucleotide consists of a phosphate group, a pentose sugar (deoxyribose in DNA), and a nitrogenous base. The phosphodiester bond occurs between the phosphate group of one nucleotide and the hydroxyl group of the adjacent nucleotide. Recall that the phosphate group is always attached to the 5' carbon on the pentose sugar. There are multiple hydroxyl groups in a pentose sugar, but the hydroxyl group involved in the phosphodiester bond is attached to the 3' carbon; therefore, the phosphodiester bond occurs between a 5' phosphate group and a 3' hydroxyl group. To cut DNA molecules, you need to break these phosphodiester bonds, which is accomplished by the enzyme phosphodiesterase. Peptide bonds are found in proteins. They are bonds that join adjacent amino acids together and are involved in the formation of a polypeptide (protein) chain. Peptidase proteins are used to break these bonds, effectively cutting proteins, not DNA.
What can you conclude about the DNA backbones in a double-stranded DNA molecule? Possible Answers:
The two strands are antiparallel; the 5' end on one strand contains a phosphate group, whereas the 5' end on the other contains a hydroxyl group
The two strands are parallel and the 5' ends on both strands contain a phosphate group
The two strands are parallel; the 5' end on one strand contains a phosphate group, whereas the 5' end on the other contains a hydroxyl group
The two strands are antiparallel and the 5' end on both strands contain a phosphate group
Correct answer: The two strands are antiparallel and the 5' end on both strands contain a phosphate group Explanation: In the nucleus, DNA is always found as a double-stranded molecule. This means that one DNA molecule consists of two DNA strands. Each strand is made up of a DNA backbone (the phosphate groups and the pentose sugars) and the bases. In a DNA molecule, the two strands are organized in such a way that the DNA backbone of one strand runs in the 5'-to-3' direction, whereas the DNA backbone of the other strand runs in the 3'-to-5' direction; therefore, the two strands are antiparallel to each other. Recall that 5' and 3' refer to the carbons on the pentose sugar. A phosphate group is found on the 5' carbon of the sugar and a hydroxyl group is found on the 3'carbon of the sugar. This means that the 5' end of each strand is always characterized by the phosphate group, and the 3' end is always characterized by the hydroxyl group; therefore, both strands will have a phosphate group at their 5' end.
What is the main difference between the backbone of an RNA molecule and the backbone of a DNA molecule? Possible Answers:
The RNA backbone contains no phosphate groups
The RNA backbone contains a pentose sugar, whereas the DNA backbone contains a hexose sugar
The RNA backbone has uracil instead of thymine
The sugar in the RNA backbone has an extra hydroxyl group
Correct answer: The sugar in the RNA backbone has an extra hydroxyl group Explanation: RNA and DNA are both types of nucleic acids; therefore, both molecules are made from nucleotide monomers. Recall that a nucleotide contains a phosphate group, a pentose sugar, and a nitrogenous base. The biggest difference between an RNA nucleotide and a DNA nucleotide is the type of pentose sugar. DNA, or deoxyribonucleic acid, contains deoxyribose sugar whereas RNA, or ribonucleic acid, contains ribose sugar. A ribose sugar contains a hydroxyl group on its 2’ carbon whereas the deoxyribose sugar contains a hydrogen; therefore, the RNA pentose sugar has an extra hydroxyl group. RNA molecules do contain the nitrogenous base uracil in place of thymine; however, bases are not part of the RNA or DNA backbone structure. The backbone only consists of the phosphate groups and the pentose sugars.
Based on the structure of DNA, what is the charge of DNA? Possible Answers:
Depends on the surrounding conditions
Explanation: Given the backbone of DNA, with the phosphate group attached to the deoxyribose via a phosphodiester bond, DNA is negatively charged. For this reason, histones - the proteins around which DNA molecules are wrapped in eukaryotes - have lots of positively charged amino acids on their DNA-binding sites. This produces a strong attractive force between DNA and histones.
Which of these can be found in the DNA backbone: I. Phosphate groupII. RiboseIII. Deoxyribose IV. Phosphodiester bond Possible Answers:
Correct answer: I, III, and IV Explanation: The backbone of DNA consists of a phosphate group and a deoxyribose. These two components are therefore connected by a phosphodiester bond. The nucleotides are not included in the backbone. Instead, they make up the "rungs" of the double helical structure of DNA, which are hydrogen bonded to the bases of the complementary antiparallel strand.
Which of the following statements are incorrect? Possible Answers:
A phosphate group, 5-C sugar, and a nitrogenous base make up a nucleotide.
In DNA, adenine pairs with thymine, and cytosine pairs with guanine.
DNA is double stranded, while RNA is single stranded.
The two strands of DNA are connected by phosphodiester bonds
The bond between the phosphate and 5-C deoxyribose sugar in DNA is called a phosphodiester bond
Correct answer: The two strands of DNA are connected by phosphodiester bonds Explanation: The two strands of DNA are actually connected by hydrogen bonds (H-bonds) between the nitrogenous bases. There are 2 hydrogen bonds between adenine and thymine, and 3 hydrogen bonds between cytosine and guanine. All other statements are true.
DNA’s backbone consists of which of the following? Possible Answers:
Purine-pyrimidine H-bonds
Correct answer: Phosphate-sugar Explanation: DNA is the hereditary material found in virtually all organisms; however, some viruses use RNA. DNA consists of several components. It has a phosphate-sugar (deoxyribose) backbone and is composed of two strands made from purine-pyrimidine hydrogen bonds in a double helix confirmation. The purines associated with DNA include adenine and guanine and the pyrimidines include cytosine and thymine. Adenine bonds with thymine and cytosine bonds with guanine.
Which of the following is not correct regarding eukaryotic DNA? Possible Answers:
DNA's bases include adenine, guanine, thymine, and cytosine.
DNA is found in the nucleus, cytoplasm, and ribosomes.
Deoxyribose is the sugar that composes DNA.
DNA runs antiparallel in a 5' to 3' direction.
Correct answer: DNA is found in the nucleus, cytoplasm, and ribosomes. Explanation: All of the responses are correct except that eukaryotic DNA is found in the nucleus, cytoplasm, and ribosomes. In eukaryotes, DNA is only found in the nucleus, mitochondria, and only sometimes free floating in the cytoplasm. DNA is not found in ribosomes. RNA on the other hand, is found in the nucleus, cytoplasm, and ribosomes. Note that since prokaryotes lack membrane-bound organelles, their DNA is free-floating in the cytoplasm.
Azka
Benedictine University, Bachelor of Science, Biology, General. Lake Erie College of Osteopathic Medicine, Master of Science, ...
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University of Pennsylvania, Bachelor of Science, Neuroscience.
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Norfolk State University, Bachelor of Science, Biology, General. UDC/Georgetown University, Master of Science, Cancer Biology...
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What parts of the nucleotides make up the sides backbone of the ladder
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