Glossary of Scientific Terms related to CRISPR-Cas
Allele: One of two (or more) alternative forms of a gene found at the same location on a chromosome.
Amino acid: The building block of proteins.
Cas: Abbreviation for “CRISPR Associated” used to designate proteins that accompany a CRISPR locus that together comprises a CRISPR-Cas defense mechanism. Cas9 is an example of a Cas protein.
Cas9: An RNA-guided endonuclease that complexes with a tracrRNA and a crRNA to introduce a double-strand break at a specific DNA sequence within a genome.
Chromosome: A threadlike molecule of DNA and the associated proteins that support its structure found in the nucleus of most living cells. Chromosomes carry genetic information in the form of genes. The number of chromosomes can be different in different organisms.
CRISPR: Acronym for “Clustered Regularly Interspaced Short Palindromic Repeats.” A piece of DNA comprising nucleotide sequences that are repeated and separated by sequences from invading viruses that serves as part of a naturally occurring CRISPR-Cas defense system in bacteria to fight invading viruses.
crRNA: Abbreviation for “CRISPR RNA.” A Small RNA molecule encoded by the CRISPR locus constituting part of a 3-component naturally occurring CRISPR-Cas defense system in bacteria. It complexes with the tracrRNA to direct the Cas9 protein to cut a specific DNA sequence.
DNA: Acronym for deoxyribonucleic acid. DNA encodes the heritable genetic information for an organism, (i.e., genetic instructions used in the growth, development, functioning and reproduction) of all known living organisms and many viruses. DNA typically exists in a double-stranded form of two polynucleotide DNA strands coiled around each other to form a double helix. It is organized into genes that specify the production of proteins. Assemblages of multiple genes are organized into chromosomes.
Double-Strand Break (DSB): A localized break in both strands of double-stranded DNA.
Endonuclease: A protein that breaks down a polynucleotide chain of DNA by cutting the internal bonds linking the nucleotides.
Genes: Regions of DNA that encode the physical and inherited characteristics of an organism.
Genome: The complete set of genes or genetic material present in a cell or organism.
Mutation: A change in the nucleotide sequence of an organism’s genome.
Nucleotide: The building blocks of DNA or RNA.
Phage (bacteriophage): Virus that infects bacteria.
Protein: Macromolecules consisting of one or more chains of amino acids that perform a vast array of functions within organisms. The amino acid sequence of a protein is encoded by the nucleotide sequence of a corresponding gene.
Protein synthesis: The cellular process of assembling amino acids into proteins using the nucleotide sequence of messenger RNA (mRNA, see “RNA”) as a set of instructions.
RNA: Acronym for ribonucleic acid. RNA is essential in various biological roles in coding, decoding, regulation, and expression of genes. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself. There are several forms of RNA, including messenger RNA (mRNA) which conveys the genetic information from genes (encoded by nucleotides) to proteins (encoded by amino acids).
sgRNA: Abbreviation for “Single Guide RNA”. Adaptation of the bacterial CRISPR-Cas system for genome editing purposes by combining crRNA and tracrRNA into a single guide RNA molecule.
tracrRNA: Abbreviation for “trans-activating CRISPR RNA.” Small RNA molecule constituting part of a 3-component naturally occurring CRISPR-Cas defense system in bacteria and serving as a link for associating the crRNA with the Cas9 protein.