8.4 Transcription KEY CONCEPT Transcription converts a gene into a single-stranded RNA molecule. NEW VOCABULARY (Def. on next 2 slides) Central Dogma RNA Transcription RNA Polymerase Messenger RNA (mRNA) Ribosomal RNA (rDNA) Transfer RNA (tRNA) MAIN IDEAS

8.4 Transcription Central Dogma A theory that states, in cells, information flows in one direction: from DNA RNA proteins. RNA Nucleic acid molecule that allows for the transmission of genetic information and protein synthesis. You can think of RNA as a temporary copy of DNA that is used, then destroyed. Transcription The process of copying a sequence of DNA to produce a complementary strand of messenger RNA. NEW VOCABULARY

8.4 Transcription VOCABULARY CONTINUED… RNA Polymerase Enzyme that catalyzes the synthesis of a complementary strand of RNA from a DNA template. Enzymes that bond nucleotides together in a chain to make a new RNA molecule. Messenger RNA (mRNA) Form of RNA that carries genetic information from the nucleus to the cytoplasm, where it serves as a template for protein synthesis. Ribosomal RNA (rRNA) RNA that is in the ribosome & guides the translation of mRNA into a protein. Forms part of the ribosomes = cell’s protein factories. Transfer RNA (tRNA) Form of the RNA that brings amino acids to ribosomes during protein synthesis.

8.4 Transcription Main Idea #1: RNA carries DNA’s instructions. The central dogma states that information flows in one direction from DNA to RNA to proteins.

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

8.4 Transcription RNA differs from DNA in three major ways. –RNA has a ribose sugar NOT a deoxyribose sugar. –Because it has one more oxygen atom. –RNA has the base uracil instead of the base thymine. –RNA is a single-stranded structure. –Remember DNA is a double stranded structure.

8.4 Transcription Transcription is catalyzed by RNA polymerase. RNA polymerase and other proteins form a transcription complex. The transcription complex recognizes the start of a gene and unwinds a segment of it. start site nucleotides transcription complex Transcription copies DNA to make a strand of RNA. Main Idea #2: Transcription makes three types of RNA.

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

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

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.

8.4 Transcription Main Idea #3 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