Molecular Genetics

The semiconservative process by which a cell copies its entire DNA genome before cell division. DNA helicase unwinds the double helix, and DNA polymerase synthesizes new complementary strands using each original strand as a template, producing two identical DNA molecules.

The process by which RNA polymerase reads a DNA template strand and synthesizes a complementary messenger RNA (mRNA) molecule. In eukaryotes, the pre-mRNA undergoes processing including 5' capping, 3' polyadenylation, and splicing before export from the nucleus.

The process by which ribosomes decode mRNA into a polypeptide chain. Transfer RNA (tRNA) molecules carry amino acids to the ribosome, where anticodons on the tRNA base-pair with codons on the mRNA, ensuring the correct amino acid sequence is assembled.

The set of mechanisms that control when, where, and how much of a gene's product is made. Regulation can occur at multiple levels including transcriptional (promoters, enhancers, transcription factors), post-transcriptional (mRNA splicing, stability), translational, and post-translational (protein modification, degradation).

A permanent change in the nucleotide sequence of DNA. Mutations can be point mutations (substitutions, insertions, deletions), chromosomal mutations (translocations, inversions), or large-scale rearrangements. They may be silent, missense, nonsense, or frameshift depending on their effect on the protein product.

The principle articulated by Francis Crick stating that genetic information flows from DNA to RNA to protein. DNA is transcribed into mRNA, which is then translated into protein. While exceptions exist (such as reverse transcription), this framework describes the primary flow of genetic information in cells.

A set of laboratory techniques used to combine DNA from different sources into a single molecule. Restriction enzymes cut DNA at specific sequences, and DNA ligase joins fragments together, allowing genes to be cloned, expressed in new organisms, or studied in isolation.

A technique that amplifies a specific DNA segment exponentially through repeated cycles of denaturation, annealing of primers, and extension by a thermostable DNA polymerase (Taq polymerase). PCR can generate millions of copies of a target sequence from a minute starting sample.

A revolutionary genome editing technology derived from a bacterial adaptive immune system. A guide RNA directs the Cas9 nuclease to a specific genomic location where it creates a double-strand break, allowing genes to be disrupted, corrected, or replaced with unprecedented precision.

Heritable changes in gene expression that do not alter the underlying DNA sequence. Key mechanisms include DNA methylation (addition of methyl groups to cytosine), histone modification (acetylation, methylation, phosphorylation), and chromatin remodeling, all of which affect how accessible genes are to the transcription machinery.