Transcription and Translation: Comprehensive Study Notes

Central Dogma

The fundamental principle of molecular biology that describes the flow of genetic information in a cell: DNA to RNA to protein, via transcription and translation.

Transcription

The process by which genetic information from a DNA template strand is copied into an RNA molecule.

Translation

The process by which a ribosome synthesizes a polypeptide (protein) from an mRNA template, using the genetic code.

Template strand (DNA)

The DNA strand that provides the template for RNA synthesis, read in the 3' \to 5' direction.

Coding strand (DNA)

The DNA strand whose sequence is identical to the RNA transcript, except that T is replaced by U.

RNA Polymerase

The enzyme that synthesizes RNA from a DNA template during transcription.

Promoter

A DNA region that signals the transcription start point and helps recruit the transcription machinery.

TATA box

A common promoter element in eukaryotes, crucial for the formation of the transcription initiation complex.

Transcription factors

Proteins that guide RNA polymerase to the promoter and regulate its binding and initiation.

Elongation (Transcription)

The stage of transcription where RNA polymerase moves along the DNA, unwinding the helix and synthesizing RNA by adding nucleotides to the 3' end of the growing RNA molecule.

Termination (Transcription)

The end stage of transcription when terminator signals are encountered on the template strand, leading to the release of the RNA transcript and RNA polymerase.

Polyadenylation signal

A signal on the eukaryotic RNA transcript (TTATTT) that helps finalize termination.

Genetic Code

The set of rules by which information encoded in mRNA nucleotide triplets (codons) is translated into the amino acid sequence of a protein.

Codon

A three-nucleotide sequence on an mRNA molecule that specifies a particular amino acid or a stop signal during protein synthesis.

Start Codon

The mRNA codon AUG, which codes for methionine and initiates translation.

Stop Codons

Three mRNA codons (e.g., UAA, UAG, UGA) that signal the termination of translation.

tRNA (transfer RNA)

Molecules that act as interpreters during translation, carrying a specific amino acid and an anticodon that base-pairs with a complementary mRNA codon.

Anticodon

A three-nucleotide sequence on a tRNA molecule that base-pairs with a complementary mRNA codon.

Ribosome

A complex of ribosomal RNA (rRNA) and proteins that serves as the site of protein synthesis (translation).

Point Mutation

A change in a single nucleotide pair of a gene.

Missense Mutation

A type of substitution mutation that changes a codon to encode a different amino acid.

Nonsense Mutation

A type of substitution mutation that changes a codon into a stop codon, often leading to a nonfunctional protein.

Silent Mutation

A type of mutation that changes a single nucleotide, but does not change the amino acid sequence encoded by the gene, due to the degeneracy of the genetic code.