DNA Transcription Protein Translation DNA Transcription l l

DNA Transcription & Protein Translation

DNA Transcription l l DNA must be copied to messenger RNA (m. RNA) in the nucleus m. RNA travels from nucleus to the ribosomes in cytoplasm Every set of three bases on m. RNA is called a codon Remember RNA has uracil (U) instead of thymine (T), it has one strand it contains the sugar ribose, not deoxyribose!

Transcription – Step I A C G T A T G C A T A G C A T DNA Strands

Transcription – Step II A C G T A T C G T A U G C A U A G C A U One side of the DNA is Matched Up with a Complementary m. RNA strand

Transcription – Step III A C G U A U G C A U A G C A U m. RNA leaves nucleus and goes to ribosomes A new complementary RNA strand is made for the other side of the DNA

Transcription Reminders l l The template strand is the DNA strand being copied The r. RNA strand is the same as the DNA strand except Us have replaced Ts

Protein Translation l l l Modified genetic code is “translated” into proteins t. RNA matches the codons (set of 3 bases on the m. RNA) with its own set of three bases (anticodon) Each piece of t. RNA brings in an amino acid – 20 amino acids

t. RNA in cytoplasm has a codon attached to an amino acid

t. RNA structure l l l 3 -base code (triplet) is an “anticodon” Protein molecule Attached amino acid that is carried from cytoplasm to ribosomes

Protein Synthesis l l Start: Ribosome binds to m. RNA at start codon (AUG) Elongation: – – – l t. RNA complexes bind to m. RNA codon by forming complementary base pairs with the t. RNA anticodon The ribosome moves from codon to codon along the m. RNA. Amino acids are added one by one Release: release factor binds to the stop codon