Chapter 14: From DNA to Protein Flashcards
transcription
copies information from a DNA sequence (a gene) to a complementary DNA sequence
translation
converts RNA sequence to amino acid sequence of a polypeptide
Messenger RNA
mRNA, carries copy of DNA sequence to site of protein synthesis at the ribosome
Transfer RNA
tRNA, carries amino acid for polypeptide assembly
Ribosomal RNA
rRNA, catalyzes peptide bonds and provides structure
messenger hypothesis
mRNA forms as a complementary copy of one DNA strand in a gene
RNA polymerases
catalyze the synthesis of RNA (does not need primers)
3 stages of transcription
Initiation
Elongation
Termination
promoter
a special sequence of DNA, that tells RNA polymerase where to start and which strand of DNA to transcribe
Elongation
RNA polymerase unwinds DNA about 10 base pairs at a time reads template in 3’ to 5’ direction
Termination
specified by DNA base sequence
genetic code
specifies which amino acid will be used to build a protein
codon
a sequence of 3 bases, which each code for an amino acid
Start codon
AUG– Invitation signal for translation
Stop codons
UAA, UAG, UGA– stop translation and polypeptide is released
ribosome
the workbench– holds mRNA and charged tRNAs in correct positions to assemble polypeptide chain
3 steps of translation
initiation
elongation
termination
translation initiation
a charged tRNA and small ribosomal subunit both bound to mRNA, large subunits join’s the complex; the charged tRNA us now in the P site of the large subunit
translation elongation
the second charged tRNA enters the A site.
Large subunit catalyzes 2 reactions:
- it breaks bind between tRNA in P site and its amino acid
- peptide bond forms between that amino acid and amino acid on tRNA in the A site
translation termination
translation ends when a stop codon enters the A site
protein modifications
proteolysis by proteases, Glycosylation– adding sugars to form glycoprotein. Phosphorilation– adding phosphate groups by kinases
