Lecture 4 Flashcards
Central Dogma of Molecular Biology
The principle of directional information flow from DNA to RNA to protein
Genetic Code
A triplet code in which combinations of three bases specify amino acids, degenerate and non-overlapping
Frameshift Mutations
Insertion or deletion of a nucleotide causing a shift in the reading frame
Primary Transcript
A newly produced RNA molecule
RNA Processing
Chemical modifications made to the primary transcript, including the removal of sequences and addition of 5’ caps/3’ tails
Poly(A) Tail
A long stretch of adenines (50 to 250 nucleotides) added to the 3’ end of an mRNA transcript, protects the mRNA from nucleases and is required for export of the transcript to the cytoplasm
5’ Cap
A guanosine that is methylated at position 7 of the purine ring, protects the mRNA from nucleases and plays a role in positioning the mRNA on the ribosome
RNA Splicing
The process of removing introns and joining the exons, splicing errors commonly cause inherited human diseases
Spliceosome
Large molecular complex consisting of 5 different RNA molecules and many proteins, catalyzes the removal of introns
snRNPs
Small nuclear ribonucleoprotein complexes, help spliceosomes assemble, contain 1 or 2 snRNA molecules
Ribozymes
RNA molecules that function as catalysts
Missense Mutation
A codon mutation which alters only a single amino acid
Silent Mutation
A codon mutation which does not alter the amino acid, but can still have an effect on splicing or ribosome stalling
Nonsense Mutation
A codon mutation which converts an amino acid-coding codon into a stop codon, leading to incomplete, nonfunctional polypeptides
Nonstop Decay
When there is no stop codon RNA degrading enzymes bind the stalled ribosome to degrade the defective mRNA
Nonsense Mediated Decay
mRNA molecules with premature stop codons will be degraded as long as premature stop is not in the final exon
Centrifuge
A piece of equipment that consists of a rotor that can be be spun rapidly in a circular motion by an electric motor
Sedimentation Coefficient
Measure of how rapidly a particle sediments when subjected to centrifugation, measured in Svedbergs
Subcellular Fractionation
Using centrifugation to isolate and purify organelles and macromolecules based on their sedimentation rates and density
