Transcription, Translation, and Cell Division

Vocabulary flashcards generated from lecture notes covering protein synthesis (transcription and translation), pre-mRNA splicing, ribosome structure, and the steps of the cell cycle including mitosis and apoptosis.

Gene

A segment of DNA that acts as a recipe for making a specific protein.

Promoter region

A region on DNA containing a start signal where RNA polymerase binds to begin transcription.

Transcription

The process of making a single-stranded messenger RNA copy from a gene on a DNA template strand.

RNA polymerase

An enzyme that unwinds DNA, reads base pairs on the template strand, and synthesizes complementary RNA nucleotides.

Messenger RNA (mRNA)

A single-stranded RNA copy of a gene that carries genetic instructions from the nucleus to the cytosol for protein synthesis.

Transfer RNA (tRNA)

A type of RNA that brings specific individual amino acids to the ribosome during translation based on complementary codon matching.

Ribosomal RNA (rRNA)

A structural component of the ribosome.

Initiation (Transcription)

The first event of transcription in which RNA polymerase unwinds DNA and binds to the promoter region.

Elongation (Transcription)

The event of transcription where RNA polymerase moves along the DNA template strand, adding complementary base pairs to the growing mRNA strand.

Termination sequence

A specific sequence of nucleotides on DNA that causes a hairpin loop to form in mRNA, triggering RNA polymerase and mRNA to release from DNA.

Template strand

The specific single strand of DNA that is read and copied by RNA polymerase during transcription.

Coding strand

The strand of DNA that is ignored and not copied during transcription.

Pre-mRNA

The initial single-stranded RNA transcript formed in the nucleus before undergoing modifications such as splicing.

Splicing

The modification process carried out by a spliceosome where non-coding introns are removed and exons are joined together to form mature mRNA.

Exons

The coding regions of pre-mRNA that are kept and joined together to create mature mRNA.

Introns

Non-coding intermediate sequences in pre-mRNA that are removed during splicing, degraded, and recycled.

Five prime cap and poly A tail

Protective modifications added to the ends of pre-mRNA to prevent degradation by enzymes in the cytosol.

Translation

The process occurring at a ribosome in the cytoplasm where the mRNA sequence is converted into a chain of amino acids to make a protein.

Codon

A sequence of three nitrogenous base pairs on mRNA that codes for a specific amino acid or stop signal.

Start codon

The specific mRNA codon sequence AUG that codes for methionine and initiates translation.

Anticodon

A sequence of three complementary base pairs located on a tRNA molecule that aligns with a codon on mRNA.

A site

The arrival site on the large subunit of a ribosome where a new tRNA carrying an amino acid first enters.

P site

The site on the ribosome where peptide bonds are formed between amino acids and where the initial tRNA enters during initiation.

E site

The exit site on the ribosome where a tRNA without an amino acid releases and leaves.

Somatic cell division

Body cell division, known as mitosis, where one cell produces two identical daughter cells for growth and repair.

Interphase

The longest phase of the cell cycle, taking approximately $23\,\text{hours}$, during which DNA, organelles, and replication machinery are duplicated.

G1 phase

The first growth phase of interphase involving cellular growth, production of new organelles, and preparation for DNA replication.

S phase

The synthesis phase of interphase in which all genetic material in the nucleus is replicated.

G2 phase

The second gap phase of interphase where centriole replication is completed and enzymes for cell division are prepared.

M phase (Mitotic phase)

The phase of the cell cycle lasting about $1\,\text{hour}$ where physical division of nuclear material and cytoplasm occurs.

PMAT

A mnemonic representing the four sequential steps of mitosis: Prophase, Metaphase, Anaphase, and Telophase.

Sister chromatids

Two identical copies of a replicated chromosome held together at the centromere.

Prophase

The first step of mitosis where chromatin supercoils into visible chromosomes, the nuclear envelope breaks down, and spindle microtubules grow.

Metaphase

The second step of mitosis where sister chromatids align along the central equatorial plate and microtubules attach to centromeres.

Anaphase

The third step of mitosis where sister chromatids are pulled apart to opposite poles and a cleavage furrow begins to form.

Telophase

The fourth step of mitosis where chromosomes reach opposite poles, the cleavage furrow deepens, and organelles divide between developing cells.

Cytokinesis

The final physical division of the cell membrane that pinches the cell into two separate, identical daughter cells.

Apoptosis

Programmed cell death, an orderly process initiated by chemical ligand signals to destroy old, damaged, or infected cells.