RNA 12.3

What is RNA?  Macromolecule made of nucleotides from DNA  Used to build proteins.

RNA is different from DNA 1.Single stranded 2.Uracil replaces Thymine 3.Ribose instead of deoxyribose 4.Can leave the nucleus

3 types of RNA 1.) mRNA  m=messenger  Long, stringy (like a snake)  Function - Carries the instructions from the nucleus to the cytoplasm to initiate translation  Codons = sequences of 3 bases  Made during transcription

2.) tRNA  t= transfer  Shaped like a “hair pin” or a T  Responsible for bringing the amino acids for translation  Contains “anti-codons” that match up with mRNA temporarily

3.) rRNA  rRNA = ribosomal  Structurally part of the ribosome organelle  Site of translation  Globular shaped

 RNA is made through “Transcription”  RNA is made in the nucleus like DNA replication

Review the steps  Transcription Unzip one gene in DNA Match up bases to one side of a gene in DNA mRNA detaches from the DNA mRNA moves out of the nucleus and into the cytoplasm

Steps in transcription  Making of RNA from DNA in the nucleus 1. Initiation at the promoter site by RNA polymerase opens up the DNA molecule 2. Elongation adds new RNA bases, including Uracil, down the exposed DNA bases 3. Termination occurs when RNA polymerase hits the “stop” signal and detaches the new single strand of RNA

In RNA: A binds with U C binds with G DNA strand: GAG AAC TAG TAC RNA: CUC UUG AUC AUG

 Animation 1 Animation 1  nimat/molgenetics/transcription.swf  Animation 2 Animation 2  web/models/eukTranscription.swf