UCI BioSci Bio 93 - Lecture 15: Transcription

Vocabulary practice flashcards covering molecular biology concepts from Lecture 15: Transcription, including DNA replication limits, telomeres, the genetic code, and the stages of transcription.

Gene Expression

The process by which DNA directs protein synthesis, including two main stages: transcription and translation.

Transcription

The DNA-directed synthesis of RNA, resulting in the production of mRNA from a DNA template.

Translation

The synthesis of a polypeptide sequence specified by mRNA, occurring mainly at ribosomes.

Central Dogma

The concept that cells are governed by a cellular chain of command: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Primary Transcript

The initial RNA transcript synthesized from any gene before undergoing RNA processing.

Telomeres

Special repetitive nucleotide sequences ($\text{TTAGGG}$) at the ends of eukaryotic chromosomes that postpone the erosion of genes near DNA ends rather than preventing DNA shortening.

Telomerase

An enzyme that catalyzes the lengthening of telomeres in germ cells to prevent gametes from missing essential genes across cell divisions.

Werner's Syndrome

A premature aging disease associated with the accelerated shortening of telomeres.

End Replication Problem

The limitation of DNA polymerase where the replication machinery cannot complete the $5'$ ends of linear eukaryotic chromosomes, producing successively shorter DNA molecules with uneven ends.

Mutations

Permanent changes in the nucleotide sequence of DNA that are passed to the next generation, providing the genetic variation upon which natural selection operates.

Genotype

The genetic makeup of an organism, which is carried in its specific sequence of nucleotide bases.

Phenotype

The physical and physiological traits of an organism that emerge as a consequence of the specific proteins expressed.

Codon

A triplet of nucleotide bases in DNA or mRNA that specifies a single amino acid or a termination signal.

Reading Frame

The correct grouping of triplet nucleotides required during translation to produce the specified polypeptide accurately.

Redundancy of the Genetic Code

The characteristic of the genetic code wherein multiple codons specify the same amino acid, with $61$ coding triplets specifying $20$ different amino acids.

Non-Ambiguity of the Genetic Code

The property that no single codon ever specifies more than one distinct amino acid.

Stop Codons

The $3$ triplet sequences (UAA, UAG, and UGA) that do not code for amino acids but signal the termination of translation.

Universality of the Genetic Code

The feature that the genetic code is shared almost identically among bacteria to complex animals, allowing genes to be transcribed and translated when transferred between different species.

Coupled Transcription and Translation

A prokaryotic process where ribosomes attach to and translate mRNA while transcription is still underway, occurring because bacteria lack a nucleus.

RNA Processing

The modification of the eukaryotic primary transcript (pre-mRNA) inside the nucleus before the mature mRNA is exported to the cytoplasm.

RNA Polymerase

An enzyme that pries apart the two DNA strands and joins complementary RNA nucleotides during transcription.

Promoter

The specific DNA sequence where RNA polymerase binds to initiate RNA synthesis.

Transcription Unit

The stretch of DNA downstream of the promoter that is transcribed into an RNA molecule.

Transcription Factors

Proteins in eukaryotes that mediate the binding of RNA polymerase and the initiation of transcription.

TATA Box

A crucial eukaryotic promoter DNA sequence that participates in forming the transcription initiation complex.

Transcription Initiation Complex

The completed assembly comprising transcription factors and RNA polymerase II bound to the promoter on DNA.

Template Strand

The DNA strand that provides the template for ordering complementary RNA nucleotides, read by RNA polymerase in the $3'$ to $5'$ direction.

Coding Strand

The nontemplate strand of DNA whose sequence matches the transcribed mRNA molecule, with thymine in place of uracil.

Elongation (Transcription)

The stage of transcription where RNA polymerase moves downstream, untwisting $10\text{ to }20$ DNA bases at a time and synthesizing RNA at a rate of $40\text{ nucleotides per second}$ in eukaryotes.

Termination (Transcription in Eukaryotes)

The stage of transcription where RNA polymerase continues transcribing after the pre-mRNA is cleaved from the growing chain until it eventually detaches from the DNA.