Keywords

Adenosine triphosphate (ATP)

Adenosine triphosphate (ATP)

An activated nucleotide composed of adenine, a ribose sugar and three phosphate groups. Acts as the universal energy currency for cells.

Anticodon

A sequence of three bases at the end of a tRNA molecule that determines the specific amino acid carried by the tRNA. Forms hydrogen bonds with the codon in mRNA during translation.

Coding (sense) strand

The strand of DNA with the same base sequence as the mRNA (except T is replaced with U in mRNA).

Codon

A sequence of three bases in mRNA that codes for one amino acid.

Complementary base pairing

Specific base pairing rules in DNA and RNA.

Deoxyribonucleic acid (DNA)

The molecule responsible for the storage of genetic information in a cell.

DNA gyrase

Unwinds a specific section of the DNA molecule.

DNA helicase

Unzips a specific section of the DNA molecule by breaking the hydrogen bonds between the two DNA strands.

Gene

A length of DNA that carries the code for the synthesis of one specific polypeptide chains or for other RNA molecules that regulate genes.

Genetic code

A sequence of three bases in DNA codes for a particular amino acid in a polypeptide chain.

Messenger RNA (mRNA)

A single stranded polynucleotide formed as a result of the transcription of a gene from the template of the DNA. Carries the information coding for a polypeptide from the nucleus to the ribosomes in the cytoplasm.

Mutation

A change to the sequence of bases in DNA.

Nucleotide

The monomer of nucleic acids consisting of a phosphate group, a pentose sugar and a nitrogen containing organic base.

Phosphodiester bond

Covalent bond joining 3’ carbon atom of one nucleotide to the 5’ carbon of another.

Polynucleotide

Larger polymer molecule made of many nucleotide monomer joined by phosphodiester bonds.

Promoter

DNA sequence at the start of a gene, to which RNA polymerase binds to start transcriptions.

Purine

Nitrogenous base consisting of a double ring structure.

Pyrimidine

Nitrogenous base with a single ring structure.

Reverse transcriptase

An enzyme originally derived from retroviruses. This enzyme catalyses the synthesis of a DNA strand using an RNA molecule as a template.

Ribonucleic acid (RNA)

Single stranded polynucleotide that exists in three forms. Each form plays a part in the synthesis of proteins within cells.

Ribosomal RNA (rRNA)

Types of RNA molecules found in both small and large subunits of ribosomes.

Ribosomes

Structures composed of two subunits, made from rRNA and proteins, which are the site of protein synthesis.

RNA polymerase

Binds to a specific binding site on the DNA at the start of the gene.

Semi-conservative replication

The replication of a DNA molecule where the two strands separate and each strand acts as a template for the synthesis of a new DNA strand according to the complementary base-pairing rule.

Template (antisense) strand

The strand of DNA that acts as the template for transcription and has a complementary base sequence to both the mRNA and the DNA coding strand.

Transcription

The process of formation of an mRNA copy of a section of the template strand of DNA that corresponds to a gene, catalysed by RNA polymerase.

Transcription factor

Protein that binds to a specific DNA sequence to alter the expression of a gene.

Transfer RNA (tRNA)

Single RNA polynucleotide chain that carries a specific activated amino acid to the ribosomes during translation to be added to the growing polypeptide chain.

Translation

The production of a polypeptide chain at a ribosome using the sequence of codons in the mRNA to direct the order amino acids are joined together.