Gene Expression & Recombinant DNA — Study Guide Flashcards

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DNA methylation

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Addition of methyl groups (usually to cytosines) that changes chromatin structure and typically represses gene transcription. It is an epigenetic mark that does not alter the DNA base sequence and can be heritable through cell divisions.

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Histone acetylation

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Attachment of acetyl groups to histone tails that generally loosens chromatin and increases transcriptional accessibility. This modification is reversible and is part of dynamic regulation of gene expression.

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Genetic imprinting

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Epigenetic phenomenon where only one allele of a gene is expressed depending on its parental origin. Imprinting involves DNA methylation and histone modifications that silence one parental copy.

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Transcription factor

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A protein that binds specific DNA sequences near promoters or enhancers to regulate transcription. Transcription factors can act as activators or repressors and recruit or block RNA polymerase.

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Promoter

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A DNA sequence upstream of a gene where RNA polymerase and transcription factors assemble to initiate transcription. Promoters determine the baseline level and timing of gene expression.

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Enhancer

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A regulatory DNA element that can increase transcription from a promoter, often functioning at a distance and in an orientation-independent manner. Enhancers bind activator proteins and help stabilize transcriptional complexes.

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Operon

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A group of bacterial genes transcribed together from a single promoter and regulated as a unit. Operons allow coordinated expression of functionally related proteins in prokaryotes.

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Alternative splicing

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A post-transcriptional process where different combinations of exons are joined to produce multiple mRNA isoforms from one gene. This increases protein diversity without changing the genome sequence.

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Cytoplasmic determinants

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Molecules localized in the cytoplasm of an egg that are unequally distributed during cell division and influence daughter cell fates. They are important in early developmental patterning.

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Ubiquitin

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A small protein that, when attached to target proteins, marks them for degradation by the proteasome. Ubiquitination regulates protein turnover and many cellular processes.

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Phosphorylation

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Covalent attachment of a phosphate group to proteins, often on serine, threonine, or tyrosine residues, which can alter activity, localization, or interactions. It is a reversible regulatory mechanism used in signaling pathways.

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RNA interference

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A cellular process where small RNAs guide the degradation or translational repression of complementary mRNAs. RNAi is used for gene regulation and as an antiviral defense mechanism in some organisms.

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Dicer

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An RNase enzyme that processes long double-stranded RNA into small interfering RNAs or microRNAs. These small RNAs are then loaded into effector complexes like RISC for gene silencing.

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RISC complex

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RNA-induced silencing complex that uses a guide small RNA to find complementary mRNA targets and mediate cleavage or translational repression. RISC is central to RNAi-mediated gene silencing.

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Restriction enzyme

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An endonuclease that recognizes specific short DNA sequences and cuts DNA at or near those sites. They are essential tools for making recombinant DNA by generating compatible ends for ligation.

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Ligase

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An enzyme that joins DNA fragments by forming phosphodiester bonds, sealing nicks after recombination or cloning steps. DNA ligase is used to assemble recombinant plasmids from inserts and vectors.

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cDNA

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Complementary DNA synthesized from an mRNA template using reverse transcriptase. cDNA lacks introns and is commonly used to clone eukaryotic protein-coding sequences for expression in bacteria.

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Transformation

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Uptake of free DNA or plasmids from the environment by a bacterium, which may then integrate the DNA into its genome by recombination. Transformation is a mechanism for horizontal gene transfer.

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Conjugation

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Direct transfer of DNA between bacteria via a sex pilus, typically mediated by conjugative plasmids carrying fertility genes. Conjugation can rapidly disseminate traits like antibiotic resistance.

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Transduction

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Transfer of bacterial DNA from one cell to another mediated by bacteriophages. During transduction, phages can mistakenly package host DNA and introduce it into new host cells for recombination.

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PCR

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Polymerase Chain Reaction is a method to exponentially amplify a specific DNA sequence using cycles of denaturation, annealing, and extension with a thermostable polymerase. It produces millions of copies of a target region for analysis or cloning.