logo

Animation: DNA and RNA Structure

by Pearson
2 views
Was this helpful ?
0
DNA and RNA Structure DNA and RNA are nucleic acids, polymers made of subunits called nucleotides. This is a close-up of one DNA nucleotide. A DNA nucleotide is composed of a nitrogenous base, phosphate group, and a deoxyribose sugar. One difference between DNA and RNA is the type of sugar their nucleotides contain. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. Ribose has one more oxygen atom than deoxyribose. DNA and RNA are each composed of four different nucleotides, which differ in their nitrogenous bases. Three of the four bases are the same in DNA and RNA- adenine, guanine, and cytosine. The fourth base in DNA is thymine. In RNA it is uracil. The nitrogenous bases guanine and adenine each have two linked rings of atoms. They are called purines. Cytosine, thymine, and uracil each have a single ring, and these three bases are called pyrimidines. For convenience, the carbon atoms in a nucleotide's sugars are numbered beginning with the carbon atom bonded to the nitrogenous base, moving around the ring, and up to the carbon that is bonded to the phosphate group. The 1 prime carbon is bonded to the nitrogenous base, the 3 prime carbon to the next nucleotide, and the 5 prime carbon to the phosphate group. DNA and RNA are polynucleotides - long chains of nucleotides. Polynucleotides are always assembled in the 5 prime to 3 prime directions. A covalent bond forms between the carbon at the 3 prime position of a nucleotide and the phosphate group at the 5 prime position of the next nucleotide. RNA usually consists of a single polynucleotide chain. DNA, on the other hand, consists of two polynucleotide chains. The two DNA chains, or strands, are oriented in opposite directions and held together by hydrogen bonds between the nitrogenous bases on opposite strands. Because of their sizes, shapes, and arrangement of polar groups, the DNA bases form complementary pairs. Adenine pairs with thymine, and cytosine pairs with guanine. The two polynucleotides in DNA wind around each other to form the familiar double helix. The bases can be in any order, like the letters of the alphabet. However, the base sequence is significant. Sequences of bases called genes encode the instructions for the structure and function of an organism.
DNA and RNA Structure DNA and RNA are nucleic acids, polymers made of subunits called nucleotides. This is a close-up of one DNA nucleotide. A DNA nucleotide is composed of a nitrogenous base, phosphate group, and a deoxyribose sugar. One difference between DNA and RNA is the type of sugar their nucleotides contain. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. Ribose has one more oxygen atom than deoxyribose. DNA and RNA are each composed of four different nucleotides, which differ in their nitrogenous bases. Three of the four bases are the same in DNA and RNA- adenine, guanine, and cytosine. The fourth base in DNA is thymine. In RNA it is uracil. The nitrogenous bases guanine and adenine each have two linked rings of atoms. They are called purines. Cytosine, thymine, and uracil each have a single ring, and these three bases are called pyrimidines. For convenience, the carbon atoms in a nucleotide's sugars are numbered beginning with the carbon atom bonded to the nitrogenous base, moving around the ring, and up to the carbon that is bonded to the phosphate group. The 1 prime carbon is bonded to the nitrogenous base, the 3 prime carbon to the next nucleotide, and the 5 prime carbon to the phosphate group. DNA and RNA are polynucleotides - long chains of nucleotides. Polynucleotides are always assembled in the 5 prime to 3 prime directions. A covalent bond forms between the carbon at the 3 prime position of a nucleotide and the phosphate group at the 5 prime position of the next nucleotide. RNA usually consists of a single polynucleotide chain. DNA, on the other hand, consists of two polynucleotide chains. The two DNA chains, or strands, are oriented in opposite directions and held together by hydrogen bonds between the nitrogenous bases on opposite strands. Because of their sizes, shapes, and arrangement of polar groups, the DNA bases form complementary pairs. Adenine pairs with thymine, and cytosine pairs with guanine. The two polynucleotides in DNA wind around each other to form the familiar double helix. The bases can be in any order, like the letters of the alphabet. However, the base sequence is significant. Sequences of bases called genes encode the instructions for the structure and function of an organism.