A1.2 nucleic acids

DNA

A double-stranded nucleic acid made of nucleotide chains that stores hereditary information in cells.

Genetic material

The information-carrying molecule in cells that can be replicated and passed from cell to cell and from parent to offspring.

Living organisms

Cell-based entities that carry out metabolism, grow, respond to stimuli, and reproduce using genetic material.

Nucleotide

The basic unit of nucleic acids, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.

Phosphates

In nucleic acids, the phosphate group that links sugars in adjacent nucleotides and forms part of the backbone.

Pentose sugars

Five-carbon sugars in nucleotides; deoxyribose in DNA and ribose in RNA.

Bases (nitrogenous bases)

Nitrogen-containing organic molecules (A, T, G, C, U) that form the coded information in DNA and RNA.

Sugar-phosphate bonding

Covalent linkage between the phosphate of one nucleotide and the sugar of the next, forming a continuous chain.

Sugar-phosphate backbone

The repeating chain of sugars and phosphates in a DNA or RNA strand that provides structural support.

DNA (as a polymer)

A long polynucleotide made of many covalently bonded deoxyribonucleotide monomers in two antiparallel strands.

RNA (as a polymer)

A single-stranded polynucleotide made of many covalently bonded ribonucleotide monomers.

Covalently bonded

Joined by a strong chemical bond formed by sharing pairs of electrons between atoms.

Continuous chain

An unbroken sequence of covalently bonded atoms forming a strand in DNA or RNA.

Nitrogenous bases

The nitrogen-containing components of nucleotides (A, T, G, C, U) that pair and form the genetic code.

RNA

Ribonucleic acid; a nucleic acid polymer that is usually single-stranded and functions in expressing genetic information as proteins.

Polymer

A large molecule made of many repeating smaller units (monomers) joined by covalent bonds.

Condensation (reaction)

A bond-forming reaction between molecules that produces a larger molecule and releases water.

Nucleotide monomers

Single nucleotide units that act as building blocks for nucleic acid polymers.

RNA polymers

Long chains of ribonucleotides linked by sugar-phosphate bonds to form RNA molecules.

DNA vs RNA – strands

DNA is usually double-stranded; RNA is usually single-stranded.

DNA vs RNA – nitrogenous bases

DNA uses A, T, C, G; RNA uses A, U, C, G (U replaces T).

DNA vs RNA – pentose sugar

DNA contains the sugar deoxyribose; RNA contains the sugar ribose.

Ribose

A five-carbon sugar with one more oxygen atom than deoxyribose, found in RNA nucleotides.

Deoxyribose

A five-carbon sugar lacking one oxygen compared with ribose, found in DNA nucleotides.

Nucleic acids

Biological polymers (DNA and RNA) made of nucleotide chains that store and transmit genetic information.

Complementary base pairing

Specific pairing of bases: in DNA, A pairs with T and C with G; in RNA, A pairs with U and C with G.

Genetic information

The coded instructions in the base sequence of DNA (and RNA) that determine inherited characteristics.

Replicated

Copied so that an identical DNA molecule is produced before cell division.

Expressed

Used so that genetic information leads to the production of functional products, usually proteins.

Complementarity

The property by which one base sequence specifically matches another via complementary base pairing.

Diversity of DNA base sequences

The huge variety of possible orders of A, T, C, and G in DNA across and within species.

Capacity for storing information

The ability of long base sequences in DNA to encode a very large amount of genetic information.

Conservation of the genetic code

The fact that the same three-base codons specify the same amino acids in almost all organisms.

Universal genetic code and common ancestry

Because nearly all organisms share the same codon–amino acid assignments, this supports the idea that they evolved from a common ancestor.