The DNA in our chromosomes contains genes that get transcribed into RNA.
There are several different types of RNA (tRNA, mRNA, rRNA, etc.). They are composed of the same building blocks but have different functions, locations and structures.
Messenger RNA (mRNA) may be translated into a protein. The standard information flow is:
DNA→RNA→Protein
The set of genes that are 'on' at any given time is critical. Different genes need to be 'on' at different times depending on the needs and functions of any particular cell.
Transcription
The goal of transcription is to make an RNA copy of a gene.
Transcription factors bind to the starting point of genes in order to identify the spot where transcription begins.
p53, Rb, the estrogen receptor are all transcription factors that malfunction in cancers.
The process of transcription is divided into several distinct steps:
Transcription factor recognizes and binds to a gene's start site (promoter).
An RNA-making enzyme (RNA polymerase) binds to the transcription factor.
The enzyme makes an RNA copy of the gene.
The enzyme falls off and the RNA is released.
The RNA will either remain in the nucleus or it will exit into the cytosol.
Translation
The goal of translation is to make a protein using the information encoded in mRNA.
The process of translation is divided into several steps:
mRNA leaves the nucleus and is recognized and bound by ribosomal subunits in the cytosol.
The ribosome 'reads' the RNA three nucleotides (one codon) at a time.
The ribosome inserts the amino acid corresponding to the codon into the growing protein.
The ribosome encounters a stop codon and terminates protein synthesis.
The protein enters a highly regulated folding process and obtains a fully folded structure.
Genes that control the proper folding, transportation, activity and eventual destruction of proteins are often damaged or malfunctioning in cancer.
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