1. 8.4 Transcription KEY CONCEPT – DNA directs the synthesis of proteins through three steps (Replication, Transcription, & Translation) Transcription is step 2 of Protein Synthesis and converts a gene into a single-stranded RNA molecule.

2. 8.4 Transcription DNA directs the synthesis of proteins through three steps (Replication, Transcription, & Translation) What was step ONE of protein synthesis?

3. 8.4 Transcription Yuuuuuhhhp,… Replication of new copies of DNA for new daughter cells.

4. 8.4 Transcription RNA carries DNA’s instructions. RNA copies the DNA’s info (in a gene) from the nucleus and takes it to the cytoplasm. The central dogma states that information flows in one direction from DNA to RNA to proteins.

5. 8.4 Transcription The central dogma includes three processes. RNA is a link between DNA and proteins. replication transcription translation – Replication – Transcription – Translation

6. 8.4 Transcription RNA differs from DNA in three major ways. –RNA has a ribose sugar (DNA has a deoxy ribose sugar.) –RNA has uracil (U), (DNA has thymine - T, instead.) –RNA is a single-stranded structure, (DNA is ?). RNA

7. 8.4 Transcription Transcription is catalyzed (started) by RNA polymerase. –RNA polymerase and other proteins form a transcription complex. Step 1. The transcription complex recognizes the start of a gene and unwinds a segment of it. start site nucleotides transcription complex

8. 8.4 Transcription –RNA polymerase bonds the nucleotides together. –The DNA helix winds again as the gene is transcribed. Step 2. Nucleotides pair with one strand of the DNA. DNA RNA polymerase moves along the DNA

9. 8.4 Transcription 3. The RNA strand detaches from the DNA once the gene is transcribed. RNA

10. 8.4 Transcription Transcription makes three types of RNA. –Messenger RNA (mRNA) carries the message that will be translated to form a protein. –Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made. –Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome (to assemble a protein).

11. 8.4 Transcription TESTIFY! What mRNA strand will be transcribed from the following DNA sequence (gene)? Gene (DNA) Sequence: A T T A G A T T A C A A T T T G A T T A C C A

12. 8.4 Transcription An-swer: Gene: A T T A G A T T A C A A T T T G A T T A C C A (only 1 of the 2 DNA strands Is copied) mRNA: U A A U C U A A U G U U A A A C U A A U G G U

13. 8.4 Transcription Summary: The transcription process is similar to replication. Transcription and replication both involve complex enzymes and complementary base pairing. The two processes have different end results. –Replication copies all the DNA; transcription copies a gene. –Replication makes one copy; transcription can make many copies. growing RNA strands DNA one gene

14. 8.4 Transcription How is DNA used by your cells? DNA stores an organism’s genetic information in sections called “genes”, the info to make one protein, in a three step process: Replication, Transcription, and Translation. There are two categories of proteins: 1)enzymes (proteins that catalyze reactions) 2)structural proteins that form parts – structures – of your cells and body.