Genotype
A genotype is the genetic makeup of an organism or the specific alleles it carries at one or more genetic locations.
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Single-nucleotide variant
A single-nucleotide variant is a difference at one DNA base position, a small change that can be harmless, useful as a marker, or important for health.
Silent mutation
A silent mutation is a DNA change that does not alter the encoded amino acid sequence, often because the genetic code has synonymous codons.
Nonsense mutation
A nonsense mutation is a DNA change that turns an amino-acid codon into a premature stop signal, often shortening the resulting protein.
Missense mutation
A missense mutation is a DNA sequence change that alters a codon so a different amino acid is placed in a protein.
Frameshift mutation
A frameshift mutation is an insertion or deletion that changes how a coding sequence is grouped into codons, often altering every downstream amino acid.
Open reading frame
An open reading frame is a stretch of DNA or RNA that can be read as codons without an internal stop signal, making it a candidate protein-coding sequence.
Aminoacyl-tRNA synthetase
Aminoacyl-tRNA synthetases are enzymes that attach the right amino acids to the right tRNAs, making accurate translation possible.
Ribosomal RNA
Ribosomal RNA, or rRNA, is the structural and catalytic RNA at the heart of ribosomes, the cellular machines that translate mRNA into protein.
Messenger RNA
Messenger RNA, or mRNA, is the RNA copy of genetic information that ribosomes read to build proteins.
Transfer RNA
Transfer RNA, or tRNA, is the adaptor molecule that matches mRNA codons with amino acids during protein synthesis.
Codon
A codon is a three-nucleotide unit in DNA or RNA that tells the translation machinery which amino acid to add, or when to stop building a protein.
Attenuation
Attenuation is a gene-regulation strategy in which transcription is stopped early, often because a growing RNA folds differently as translation responds to nutrient levels.
Rho factor
Rho factor is a bacterial protein motor that helps terminate transcription by catching RNA polymerase on certain transcripts and releasing the RNA.
Sigma factor
A sigma factor is a bacterial transcription-initiation protein that helps RNA polymerase find the right promoters and start copying DNA into RNA.
Riboswitch
A riboswitch is a structured RNA element that can bind a small molecule and change gene expression without needing a separate regulatory protein.
Trp operon
The trp operon is a bacterial gene-control system that reduces tryptophan-making enzymes when tryptophan is already plentiful.
Lac operon
The lac operon is a classic bacterial gene-control circuit that turns lactose-use genes on when lactose is available and preferred glucose fuel is scarce.
Operon
An operon is a cluster of genes controlled together by shared regulatory DNA, usually in bacteria and archaea. Operons let cells transcribe related genes as one unit and adjust gene expression in response to nutrients or other conditions.
Transcription factor
A transcription factor is a protein that helps regulate gene transcription. Many transcription factors bind specific DNA sequences at promoters, enhancers, or other regulatory elements and influence whether RNA polymerase starts or changes transcription.
Enhancer
An enhancer is a regulatory DNA element that can increase transcription of a target gene. Enhancers bind transcription factors and can act over long genomic distances, often through chromatin looping that brings them near promoters.
Promoter
A promoter is a DNA region that helps start transcription of a gene. It provides binding sites for RNA polymerase and regulatory proteins, helping cells decide where and when RNA synthesis begins.
CpG island
A CpG island is a stretch of DNA with a high frequency of cytosine-guanine CpG sites, often near gene promoters. CpG islands are important in genome annotation, transcription regulation, and DNA methylation studies.
DNA methylation
DNA methylation is an epigenetic modification in which methyl groups are added to DNA bases. In many eukaryotes, methylation at CpG sites helps regulate gene activity, genome stability, development, and cell identity.
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