TRANSCRIPTION

DNA replication

The process by which parent cells transmit their genetic information to daughter cells.

Central Dogma of Molecular Biology

The framework for understanding the flow of genetic information: DNA -> RNA -> Protein.

Transcription

The process by which genetic information in DNA is transcribed into messenger RNA (mRNA).

Genotype

The genetic makeup of an organism.

Phenotype

The observable characteristics of an organism, determined by its genotype.

Junk DNA

DNA segments that do not code for proteins and are not expressed.

mRNA

Messenger RNA, the RNA copy of a gene that is translated into a protein.

RNA polymerase

The enzyme that synthesizes RNA using DNA as a template.

Template Strand

The DNA strand that is used as a guide for RNA synthesis during transcription.

Coding Strand

The DNA strand that has the same sequence as the RNA transcript, except for the substitution of thymine (T) with uracil (U).

Promoter region

A DNA sequence that signals the RNA polymerase where to start transcription.

Sigma factor

A subunit of RNA polymerase that helps it bind to the promoter region of DNA.

Intrinsic termination

A method of terminating transcription that relies on the formation of a hairpin loop in the RNA.

Rho-dependent termination

A method of terminating transcription that requires the rho protein to catch up to the RNA polymerase.

Operon

A group of genes that are regulated together, including a promoter and one or more structural genes.

Lac operon

An operon that regulates the metabolism of lactose in bacteria and includes genes for beta-galactosidase.

Catabolite repression

A regulatory mechanism in which the presence of a preferred energy source (glucose) suppresses the expression of genes involved in the metabolism of other sources of energy (like lactose).

Tryptophan operon

An operon that regulates the synthesis of tryptophan and is controlled by the availability of tryptophan.

Attenuation

A regulatory mechanism in which the formation of secondary structures in mRNA can terminate transcription depending on the levels of metabolites such as tryptophan.

Pre-initiation complex

A complex formed by transcription factors and RNA polymerase at the promoter region before transcription begins.

5' cap

A modified guanine nucleotide added to the 5' end of eukaryotic mRNA that protects it from degradation.

Poly A tail

A stretch of adenine nucleotides added to the 3' end of eukaryotic mRNA that aids in export from the nucleus and stability.

Introns

Non-coding regions of a gene that are transcribed but removed during mRNA processing.

Exons

Coding regions of a gene that are expressed and remain in the mRNA after splicing.