What have we learned?

1. What have we learned? RNA • Which nucleic acid is like a blueprint? • Which nucleic acid is like a master plan? • The process of making two new strands of DNA is called ________. It takes place in the _____. • The process of making an mRNA strand is called______. It takes place in the _____. • What is the principal enzyme used during each process? DNA DNA replication nucleus transcription nucleus DNA polymerase is used in replication to link nucleotides. RNA polymerase is used in transcription to link nucleotides.

2. Translation • Assembling a protein using the instructions carried by mRNA • Where? Ribosomes! Nucleus Messenger RNA is transcribed in the nucleus. mRNA

3. Proteins • Proteins are chains ofamino acids(AA) • Proteins are also calledpolypeptide chains • There are 20 amino acids. Examples: • Methionine (Met) • Serine (Ser) • Valine (Val) • Alanine (Ala) • Different proteins have different AA sequences: Met – Val – Ala – Cys – Val - Ser

4. The Genetic Code • Codon= three consecutive nucleotides on mRNA • Each codon specifies an AA: • AUG -> Methionine (Met) • UCA -> Serine (Ser) • The sequence of codons on mRNA determine the sequence of AA’s in the protein

5. The Genetic Code mRNA: UCGCACGGU UCG-CAC-GGU Ser – His - Gly

6. Types of RNA • mRNA– messenger RNA • Carries instructions from nucleus to ribosome for protein synthesis • rRNA– ribosomal RNA • What ribosomes are made of (made in the nucleolus) • tRNA– transfer RNA • Carry AA’s from the cytoplasm to ribosome as proteins are assembled

7. tRNA • Carries an AA on one end • Has ananticodonon the other end • Anticodon is complementary to the codon on mRNA • What is the anticodon for UCG? • What is the anticodon for CAC? • What is the anticodon for GGU?

8. What did you just write down? translation • The process of making a protein from the codes on mRNA is called_________. • How many RNA base pairs (nucleotides) make an amino acid? • What are three base pairs (nucleotides) on the mRNA strand called? • What are the three base pairs (nucleotides) on the tRNA called? • tRNA carries __________ to the ______ • Proteins are made up of a chain of ______ three codon anticodon amino acids (aa) ribosome aa

9. Nucleus Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA 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. Methionine Ribosome Start codon mRNA Translation

10. 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. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Ribosome Translation direction