1. Structure and Function of RNA

2. RNA- ribonucleic acid  RNA is a single strand  RNA is made up of smaller subunits called nucleotides  Nucleotides consist of: Sugar-ribose phosphate group nitrogen base-4 types Adenine-A Uracil- U Guanine- G Cytosine- C

3. Adenine(A) pairs with Uracil(U)and Cytosine(C) pairs with Guanine(G) There are 3 kinds of RNA 1. messenger(m) RNA- carries nucleotide sequence from nucleus to ribosome 2. transfer(t) RNA-picks up amino acids in cytoplasm and carries them to ribosome 3. ribosomal(r) RNA- found in ribosome, joins mRNA and tRNA

5. Transcription  The process that makes messenger RNA from DNA.  Occurs in the nucleus.  DNA unzips into 2 separate strands.  Free floating RNA nucleotides in the nucleus pair up with these DNA nucleotides Cytosine(C) pairs with Guanine(G) Uracil(U) pairs with Adenine(A)

6.  After all the pairing is done, a single strand of RNA has been produced.  It is complimentary to one side of the DNA molecule.  Genetic code from DNA is transferred to mRNA.  A codon is a set of 3 nitrogen bases on mRNA.

7. RNA DNA RNA polymerase Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Go to Section:

8. Translation  Conversion of mRNA into amino acid sequence that makes up a protein.  The mRNA leaves the nucleus and enters the cytoplasm and attaches to a ribosome.  The mRNA is read by ribosomes 3 nucleotides (codon- A G C) at a time.

9. tRNA (anticodon) brings the appropriate amino acids to the ribosome.  They are assembled in a long chain called a protein.

11. Messenger RNA Messenger RNA is transcribed in the nucleus. Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. mRNA Start codon Ribosome Methionine Phenylalanine tRNA Lysine Nucleus Figure 12–18 Translation Section 12-3 mRNA Go to Section:

12. The Polypeptide “Assembly Line” The ribosome joins the two amino acids— methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. mRNA Ribosome Translation direction Lysine tRNA Ribosome Growing polypeptide chain mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Figure 12–18 Translation (continued) Section 12-3 Go to Section:

13. Practice DNA codemRNA code ACGTAGACGTAG UCGAUAUCGAUA UGCUGC AUCAUC AGCAGC UAUUAU

14. Section 12-3 Go to Section:

15. DNAmRNAtRNAAmino Acid CAT GUC AAU AUG ACG TAT GAU