Chapter 14 - Protein Synthesis

These flashcards cover key terms and concepts related to protein synthesis as discussed in the lecture.

Transcription

copying a segment of DNA into messenger RNA (mRNA).

Translation

codons in mRNA is converted into the corresponding sequence of amino acids to form a protein.

Pre-mRNA

The initial RNA transcript that is processed to form mature messenger RNA (mRNA).

Spliceosome

A complex of proteins and RNA that removes introns from pre-mRNA and splices exons together.

Introns

Non-coding segments of RNA that are removed during RNA processing.

Exons

Coding segments of RNA that are spliced together to form mature mRNA.

tRNA (transfer RNA)

Molecule that carries amino acids to the ribosome and matches them to the mRNA codons.

Aminoacyl-tRNA synthetase

An enzyme that attaches the correct amino acid to its corresponding tRNA.

Poly-A tail

A stretch of adenine nucleotides added to the 3’ end of mRNA to enhance stability and facilitate export from the nucleus.

Signal peptide

A short peptide that directs the transport of a protein to its destination in the cell.

gene expression (proteins) in bacteria, eukarya, and archaea

• Bacteria: simultaneously transcribes and translates the same gene

• Eukarya: transcription and translation are separated by nuclear envelope

• Archaea: transcription and translation are likely coupled like bacteria

Mutagen

An agent that increases the likelihood of mutations in DNA.

spontaneous mutation

can occur during DNA replication

often repairs itself

Point mutation

A change in a single nucleotide in the DNA sequence. no effect as amino acid remains the same

Missense mutation

A type of point mutation that results in a change in one amino acid in the protein, but still functional

Nonsense mutation

A type of point mutation that creates a premature stop codon in the protein sequence… no protein

base pair insertion/deletion (Frameshift) mutation

A mutation caused by insertions or deletions of nucleotide that alters the reading frame of the genetic message.

Polyribosome

A complex of multiple ribosomes translating a single mRNA strand simultaneously.

Chaperon proteins

Proteins that assist in the proper folding of other proteins.

Release factor

A protein that recognizes the stop codon during translation and triggers the release of the newly synthesized polypeptide.

Ribosome

A molecular machine that facilitates the translation of mRNA into protein.

mutagen example - osteogenesis imperfecta

a genetic disorder caused by mutations in collagen genes (poor collagen), leading to brittle bones.

post-translating

Translation is not always sufficient to make functional protein

• polypeptide chains are modifies after translation (chaperon proteins are used)

• completed proteins are targeted to specific sites in the cell (and sometimes out)

free vs bound ribosomes

polypeptide synthesis begins in cytosol, if they are meant to be bound they are marked with a signal peptide

signal-recognition particles (SRP) binds to signal peptide and delivers it to the ER