Transcription
Process of copying a gene into RNA form. Similar to DNA replication, except it’s only 1 strand 
- DNA strand is template for RNA
- Transcription occurs in the nucleus
- Base pairing rules of RNA
Steps
- RNA polymerase binds to promoter in DNA. Unwinds small portion of DNA = “transcription bubble”
- RNA polymerase “reads” DNA strand. Assembles RNA strand with complementary nucleotides. Once strand is read, DNA winds back up.
- RNA polymerase reaches terminator in transcription bubble. Releases from DNA strand. New RNA strand is released.
Product = different types of RNA
- rRNA - Part of ribosomes
- tRNA - Brings amino acids to ribsomomes
- mRNA - Tells ribosomes what protein to make

Post-transcriptional modifications: finishing touches to new RNA
Introns
- Segments of genes that don’t code for proteins
- These aren’t needed to make proteins so they’re removed from new RNA
Exons
- Encode for proteins ; kept
Alternative splicing
- Using one copy of RNA (blueprint) to make several different types of proteins
- Used for efficiency


Translation
Using mRNA to build proteins from amino acids
- Occurs in the cytoplasm
- Amino acids, ribosomes, and RNAs used during translation
- Transcription made 3 types of RNA (rRNA, tRNA, mRNA)
- RNAs exit nucleus into cytoplasm
Steps
Initiation
- mRNA binds with ribosome. Tells ribosome what protein to make. Initiator tRNA brings the first amino acid to start the process - called start codon
Elongation
- tRNA brings the amino acids to ribosomes to build the protein. Amino acids are assembled in a specific order for a specific protein.
Termination
- Last amino acid added to protein chain - called stop codon. Newly made protein is released by the ribosome.
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