Transcription

Central Dogma What is a Dogma? Process of DNA RNA protein a principle laid down by an authority as incontrovertibly true Process of DNA RNA protein

RNA Structure & Function Single-strand found in both nucleus & cytoplasm Composed of nucleotides Each nucleotide has 3 parts Phosphate 5-C sugar--Ribose 4 possible nitrogen bases Adenine and guanine Cytosine and uracil (uracil replaces thymine) Gene Expression Segment of DNA  codes for a polypeptide

Types of RNA (Overview) mRNA- carries genetic information from the DNA out to ribosomes rRNA- composes ribosomes, site of protein assembly tRNA- brings in amino acids to the ribosomes

Learning Check! What are the similarities between RNA and DNA? What are the differences between RNA and DNA?

Transcription Transcription Makes RNA from a DNA template 3 phases-initiation, elongation, termination

Transcription Initiation RNA polymerase binds to a promoter region RNA Polymerase unwinds DNA

Transcription Elongation RNA polymerase adds complementary RNA nucleotides

Transcription Termination RNA Polymerase reaches termination sequence DNA rewound Methyl Cap & poly-A tail added (makes it more stable)

Processing Occurs in the nucleus Both prokaryotic and eukaryotic cells undergo this process Primary mRNA  mature mRNA

Processing Step 1: Primary mRNA contains bases complementary to both intron and exon segments of DNA

Processing Step 2: Intron sequences are removed,

Processing Step 3: Ribozyme (RNA enzyme) splices exon segments together https://www.youtube. com/watch?v=YgmoHt LGb5c https://www.youtube.com /watch?v=o0BQJbLNYSg

Learning Check! Explain how RNA is modified before leaving the nucleus. What happens during transcription? What does RNA polymerase do (several jobs)?