Glossary
Alternative Splicing
A process that allows different combinations of exons from a single gene to be joined together, leading to the production of multiple distinct mRNA molecules and protein variants.
Example:
Through alternative splicing, a single gene can produce different protein isoforms, allowing for greater protein diversity from a limited number of genes.
Central Dogma
The fundamental principle of molecular biology stating that genetic information flows from DNA to RNA to protein.
Example:
The Central Dogma explains how the instructions in your genes are ultimately used to build all the proteins in your body.
Coding Strand
The DNA strand that has the same sequence as the mRNA transcript (with thymine replaced by uracil), but is not directly used as a template during transcription.
Example:
The coding strand of DNA for a gene will look almost identical to the mRNA produced, except for the T's being U's in the RNA.
Exons
Coding regions within a eukaryotic gene that are transcribed into RNA and are retained and joined together to form the mature mRNA molecule.
Example:
The exons contain the actual genetic instructions that will be translated into the amino acid sequence of a protein.
GTP Cap
A modified guanine nucleotide added to the 5' end of eukaryotic mRNA transcripts, which protects the mRNA from degradation and helps ribosomes recognize it for translation.
Example:
The GTP Cap acts like a 'start' signal and protective helmet for the mRNA, ensuring it's properly recognized by the ribosome.
Introns
Non-coding regions within a eukaryotic gene that are transcribed into RNA but are subsequently removed from the primary transcript during splicing.
Example:
During mRNA processing, the introns are cut out, leaving only the coding sequences to be translated.
Poly-A Tail
A string of adenine nucleotides added to the 3' end of eukaryotic mRNA transcripts, which protects the mRNA from degradation and aids in nuclear export.
Example:
Without a Poly-A Tail, an mRNA molecule would quickly be broken down by enzymes in the cytoplasm, preventing efficient protein synthesis.
RNA
A nucleic acid polymer that plays crucial roles in gene expression, carrying genetic information, and catalyzing biochemical reactions.
Example:
Unlike DNA, RNA often exists as a single strand and contains uracil instead of thymine.
RNA Polymerase
An enzyme that catalyzes the synthesis of an RNA strand from a DNA template during transcription.
Example:
To initiate gene expression, RNA Polymerase binds to the promoter region of a gene, unwinding the DNA helix.
Splicing
The process in eukaryotic cells where non-coding regions (introns) are removed from the primary RNA transcript, and coding regions (exons) are joined together.
Example:
After transcription, the pre-mRNA undergoes splicing to remove unnecessary sequences before it can be translated into a protein.
Template Strand
The DNA strand that serves as the guide for RNA polymerase during transcription, providing the sequence from which the RNA molecule is synthesized.
Example:
If the template strand of DNA is 3'-TAC-5', the RNA polymerase will synthesize an mRNA codon of 5'-AUG-3'.
Transcription
The process by which genetic information from a DNA template is copied into a complementary RNA molecule.
Example:
Before a protein can be made, the gene's DNA sequence must undergo transcription to produce an mRNA copy.
Translation
The process by which the genetic information carried by mRNA is decoded at the ribosome to synthesize a specific protein.
Example:
Once the mRNA reaches the ribosome, translation begins, converting the nucleotide sequence into an amino acid sequence.
mRNA
Messenger RNA carries genetic information from DNA in the nucleus to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis.
Example:
After transcription, the mRNA molecule leaves the nucleus to deliver the genetic code for a specific protein to the ribosome.
rRNA
Ribosomal RNA is a major structural and catalytic component of ribosomes, facilitating the binding of mRNA and tRNA and catalyzing peptide bond formation.
Example:
The ribosome, where proteins are made, is largely composed of rRNA, which helps organize the process.
tRNA
Transfer RNA molecules are responsible for bringing specific amino acids to the ribosome during translation, matching them to the codons on the mRNA.
Example:
During protein synthesis, each tRNA molecule acts like a delivery truck, ensuring the correct amino acid arrives at the growing polypeptide chain.