dna vocab

Sugar-phosphate backbone

In a polynucleotide (DNA or RNA strand), the alternating chain of sugar and phosphate to which nitrogenous bases are attached.

DNA polymerase

A large molecular complex that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.

Ligase

An enzyme, essential for DNA replication, that catalyzes the covalent bonding of adjacent DNA polynucleotide strands.

Helicase

an enzyme that unwinds the double helix of a DNA molecule, separating it into two single-stranded molecules during replication.

Deoxyribonucleic acid

A double-stranded helical nucleic acid molecule consisting of nucleotide monomers with deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T). Capable of replicating, DNA is an organism's genetic material.

Nucleotides

A building block of nucleic acids, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.

Semi-conservative model

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.

RNA polymerase

A large molecular complex that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

Transcription

The synthesis of RNA on a DNA template.

Translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of 'language' from nucleotides to amino acids.

Codons

A three-nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination signal; the basic unit of the genetic code.

Double Helix

The form of native DNA, referring to its two adjacent polynucleotide strands interwound into a spiral shape.

Introns

An internal, noncoding region of a gene that does not become part of the final messenger RNA molecule and is therefore not expressed.

Mutation

A change in the genetic information of a cell; the ultimate source of genetic diversity. can occur in the DNA or RNA of a virus.

Exons

The part of a gene that becomes part of the final messenger RNA and is therefore expressed.

Ribosome

A cell structure consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm. In eukaryotic cells, the ribosomal subunits are constructed in the nucleolus.

Transfer RNA

A type of ribonucleic acid that functions as an interpreter in translation. has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.

Ribosomal RNA

The type of ribonucleic acid that, together with proteins, makes up ribosomes; the most abundant type of RNA in most cells.

Start codon

On mRNA, the specific three-nucleotide sequence (AUG) to which an initiator tRNA molecule binds, starting translation of genetic information.

Messenger RNA

The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences.

Silent mutation

A mutation in a gene that changes a codon to one that codes for the same amino acid as the original codon. The amino acid sequence of the resulting polypeptide is thus unchanged.

Missense mutation

A change in the nucleotide sequence of a gene that alters the amino acid sequence of the resulting polypeptide. In a a codon is changed from encoding one amino acid to encoding a different amino acid.

Anticodon

On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA.

Nonsense mutation

A change in the nucleotide sequence of a gene that converts an amino-acid-encoding codon to a stop codon. It results in a shortened polypeptide.