Understanding the DNA Backbone - Biology

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.

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 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.