Gene Expression
This molecule forms the essential information bridge between DNA and proteins.
What is mRNA?
These three-nucleotide “words” of mRNA specify amino acids during translation.
What are codons?
This DNA segment acts as the “on/off switch” for bacterial operons.
What is the operator?
This concept explains how cells with identical genomes express different subsets of genes.
What is differential gene expression?
This 20-amino-acid sequence directs polypeptides to the ER for secretion or membrane insertion.
What is the signal peptide?
This eukaryotic DNA sequence, rich in adenines and thymines, is crucial for formation of the transcription initiation complex.
What is the TATA box?
These noncoding segments of pre-mRNA must be removed before translation.
What are introns?
This specific class of proteins must bind to a eukaryotic promoter before RNA polymerase II can recognize the start point of transcription.
What are general transcription factors?
This protein group links activators at enhancers to general transcription factors at the promoter.
What are mediator proteins?
This phenomenon at the third position of a codon allows some tRNAs to recognize multiple codons.
What is wobble?
These two modifications at the ends of a pre-mRNA transcript increase stability and facilitate export from the nucleus.
What are the 5′ cap and poly-A tail?
These RNA–protein complexes carry out intron removal and exon ligation.
What are spliceosomes?
Groupings of distal control elements that activate transcription when bound by specific proteins.
What are enhancers?
This specific chemical modification of histones condenses chromatin and decreases transcription, despite not altering DNA sequence.
What is histone methylation?
This irreversible developmental step ensures a cell will follow a specific fate even if transplanted to a different location in the embryo.
What is determination?
Unlike DNA polymerase, RNA polymerase does not require this molecule to begin synthesis.
What is a RNA primer?
This process allows a single gene to produce multiple polypeptides depending on which exons are retained.
What is alternative RNA splicing?
These small single-stranded RNAs degrade target mRNAs or block translation by complementary base pairing.
What are microRNAs (miRNAs)?
Attaching this small protein tags cellular proteins for destruction by a proteasome.
What is ubiquitin?
Translation proceeds along the mRNA in this direction, which corresponds to synthesis of the polypeptide from the N-terminus toward the C-terminus.
What is 5′ → 3′ on the mRNA?
These enzymes attach the correct amino acid to its corresponding tRNA.
What are aminoacyl-tRNA synthetases?
These structures, consisting of multiple ribosomes translating a single mRNA simultaneously, greatly increase protein production.
What are polyribosomes (or polysomes)?
siRNAs mediate this process, used widely in labs to experimentally silence genes.
What is RNA interference (RNAi)?
Nucleotide sequences in this region influence how long an mRNA persists before degradation.
What is the 3′ UTR (untranslated region)?
This phenomenon explains how maternal or paternal alleles of specific genes may be selectively expressed due to methylation patterns established early in development.
What is genomic imprinting (an epigenetic phenomenon)?