Central Dogma of Molecular Biology
DNA > transcription > RNA > translation > Protein
explanation of the flow of genetic information
RNA Polymerase
makes mRNA from DNA
mRNA
messenger RNA, Hold copy of DNA in RNA form for sequencing outside of the nucleus
mRNA editing steps
mRNA has to parts, exons and introns
in nucleus, SPLICOSOME COMPLEX makes cuts in mRNA
introns are removed and exons are kept, mRNA is now “mature”
a “poly-a tail” is added to the 3’ end and a GTP5 cap is added on the 5’ end
poly-a tail function
attached to the 3’ end of mRNA to slow down the destruction of mRNA in the cytoplasm
GTP5 cap funtion
guides mRNA to destination and helps it to leave the nucleus
ribosome function
reads mRNA 5’>3’ in codons (nucleotide triplets)
uses EPA complex (arrival, processing, exit)
Start/Stop codons
Start: AUG (makes amino acid)
Stop: UAA, UAG, UGA (no amino acid)
tRNA
transfer RNA, contain amino acid and anti-codon (matches with mRNA) and helps to build poly-peptide chain. made in nucleolus
Mutation
any change in genes, not always bad
mutation at DNA level: significant impact
mutation at RNA level: minor impact but more likely because of lack of “proofreading”
mutation to somate cells isnt passed on, mutation to germ cells is passed to offspring
causes of mutation
induced (outside factor) or spontaneous (copying error)
induced mutation example
radiation, chemicals, infectious agents
spontaneous mutation examples
DNA copying, alternative splicing
types of mutations
silent, missense, frame shift, nonsense (from least to most impactful)
silent mutation
nucleotide is changed but amino acid product isnt affected
missense mutation
one amino acid in change but the rest remain the same
frame shift mutation
insertion or deletion of nucleotide that shifts the “reading frame” of the ribosome.
nonsense mutation
missense or frame shift mutation that results in a premature stop codon