transcription and translation

mRNA

specifies the amino acid sequence of a protein

tRNA

binds to specific amino acid and serves as adapter molecule when amino acids are incorporated into growing polypeptide chain

rRNA

has both structural and catalytic (ribozyme) roles in ribosome

Replication

 DNA multiplies

Transcription

• DNA —> mRNA; Info from DNA is copied as RNA

Translation

 mRNA —> Protein; Polypeptides are synthesized as protein

DNA Polymerase

 enzyme that helps with DNA replication

RNA Polymerase

enzyme that helps with DNA transcription

Ribosome

organelle that serves as the site of protein synthesis

DNA

stores genetic information

RNA

 template of protein synthesis

Prokaryotes

• 70s ribosome

• Transcription in cytoplasm

• Polycistronic RNA

• RNA goes straight to translation

Eukaryotes

• 80s ribosome

• Transcription in nucleus

• Monocistronic RNA

• pre-mRNA must be edited before translation 

  • Introns (filler) and exons (actual code)

    • Introns are removed while exons are expressed

  • 5’ cap, splicing, poly-A tail

Coding strand

• 5’ to 3’

• Looks like mRNA code except Ts instead of Us

Template strand

• 3’ to 5’

• Serves as the template for RNA synthesis

Types of Mutations

• Base pair substitutions

• Insertion/Deletion

• Nucleotide analogs

• Nucleotide-altering chemicals

• Frameshift Mutagens

Effects of Mutations

• Silent Mutations: no effect

• Missense Mutations: shifts amino acid sequence

• Nonsense Mutations: end protein sequences early