RNA and the genetic code

central dogma

RNA-DNA-protein

initiation

AUG, methionine

termination

UAA, UGA, UAG

point mutations

genetic mutation where a single nucleotide base is changed, inserted, or deleted from an RNA or DNA sequence

silent mutations

no effect on protein synthesis

nonsense mutations

truncation, produces a premature stop codon

missense mutations

produces a codon that codes for a different amino acid

frameshift mutation

result from nucleotide addition or deletion, change the reading frame of subsequent codons

RNA vs DNA

ribose sugar instead of deoxyribose, uracil for thymine, single stranded instead of double stranded

messenger RNA

carries the message from DNA in the nucleus via transcription of the gene into the cytoplasm for translation

transfer RNA

brings in amino acids, recognizes the codon on the mRNA using its anticodon

ribosomal RNA

makes up much of the ribosome, enzymatically active

transcription

occurs in the nucleus

posttranscriptional modifications

7-methylguanylate triphosphate cap added to 5’ end, poly-a tail added to 3’ end, splicing done by spliceosomes to remove introns and ligate exons

alternative splicing

combines different exons to acquire different gene products

translation

occurs at the ribosome, three stages; initiation, elongation, termination

posttranslational modifications

folding by chaperones, formation of quaternary structures, cleavage of proteins or signal sequences, covalent addition of other biomolecules

jacob-monod model

operons are inducible or repressible clusters of genes transcribed as a single mRNA

transcription factors

search for promoter and enhancer regions in the DNA

promoters

within 25 base pairs of the transcription start site

enhancers

are more than 25 base pairs away from the transcription start site

osmotic pressure

a colligative property, is the pressure applied to a pure solvent preventing osmosis and is related to the concentration of the solution

pinocytosis

the ingestion of liquid into the cell from vesicles formed from the cell membrane

phagocytosis

the ingestion of solid material into the cell from vesicles