RNA: Structure & Function Section 12-3 pp

What is RNA?  RNA is a nucleic acid called Ribonucleic Acid  Helps the cell use the information in the DNA to make proteins.  There are 3 types of RNA  Each type has a specific shape  The shape of each helps it do its specific job

The Structure of RNA (Similar to DNA with several key differences)  Made of nucleotides similar to DNA (phosphate, sugar, nitrogen base)  The sugar in RNA is called Ribose  Contains the nitrogen base Uracil instead of Thymine.  Uracil binds to Adenine  RNA is a single strand

Messenger RNA (mRNA)  mRNA- carries message from DNA (nucleus) to the ribosomes (cytosol)  Long, straight strand – shape helps the cell read the code (bases) easily

Transfer RNA (tRNA)  tRNA- carries amino acids to the ribosome and helps assemble them in the correct order  Cloverleaf shape – helps it attach to both the amino acid and the ribosome

Ribosomal RNA (rRNA)  rRNA- structural component of the ribosomes  Single strand in a globular shape

How do we get RNA from the DNA message? The word “transcribe” means to copy Transcription “copies” the DNA message onto a piece of RNA DNA stays in the nucleus, where it is protected, RNA travels outside the nucleus

Transcription is… The process of making RNA from DNA All 3 types of RNA are made through transcription. Location: Takes place in the nucleus of a cell

Transcription Animations DsntUhttp:// DsntU c3yU&feature=relatedhttp:// c3yU&feature=related t/molgenetics/transcription.swfwww.stolaf.edu/people/giannini/flashanima t/molgenetics/transcription.swf

Transcription Steps Step 1: RNA polymerase binds to the promoter. - Promoter - DNA sequence that signals start of transcription. Step 2: RNA polymerase breaks the hydrogen bonds, and separates the DNA strands. Step 3: RNA polymerase builds a new RNA strand onto one DNA strand. - Uses the same base-pairing rules, but A bonds with U instead of T!

Transcription Steps Step 4: RNA polymerase reaches the termination sequence. - Termination sequence – DNA sequence that signals the end of transcription. - RNA polymerase and the new RNA strand are released from the DNA and the DNA recoils. Step 5: The RNA strand moves out of the nucleus through a nuclear pore into the cytosol.

Transcription Animation

Let’s Transcribe some DNA…  DNA strand: A A T C C G T A T T  RNA strand: U U A G G C A U A A one more time…..  DNA strand: T A G C C T T G A T  RNA strand: A U C G G A A C U A And what are those base pairing rules we follow for transcription?