1. Review of Protein Functions

2. Protein Synthesis  Protein synthesis is divided into two phases: TRANSCRIPTION and TRANSLATION  Transcription A.RNA polymerase unzips DNA (NOT making more DNA, just reading it) B.Free RNA nucleotides are base-paired with the exposed DNA nucleotides and assembled into a messenger RNA (mRNA) molecule by RNA polymerase.

3.  The mRNA molecule leaves the nucleus and moves to a ribosome in the cytoplasm  Draw Fig 12-14, pg 301 RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only)

5. II. Translation (4 Stages) A.Amino Acid Activation Stage 1.The amino acids are attached to their appropriate tRNA molecules. 2.Specific enzymes bind each tRNA with only one specific amino acid. 3.This process begins during transcription. 4.A molecule of ATP transfers its high energy bond to the activated tRNA.

6. B.Initiation Stage 1.The ribosome moves along the mRNA molecule, but nothing happens until the codon (AUG) is read. 2.AUG is known as the “Start Codon” and it codes for the amino acid f-methionine. 3.When this codon is reached, the elongation stage begins.

7. C. Elongation Stage (3 Steps) 1. New incoming tRNA matches its anti-codon with the mRNA codon. a. At the start, step 1 is repeated one time mRNA tRNA amino acid Ribosome b. Notice how the tRNA anti-codon pairs with the mRNA codon.

8. 2. The amino acid on the first tRNA is transferred to the amino acid on newly arrived tRNA.

9. 3. The empty tRNA leaves. a. Now another tRNA positions itself beside the 2 nd tRNA and amino acids are transferred from the 2 nd tRNA to the 3 rd tRNA

10. b. The ribosome continues along the mRNA molecule and steps 1,2 and 3 are repeated over and over again. What do we call this string of amino acids?

11. D. Termination phase 1.Elongation continues until a stop codon is reached. a.An mRNA codon (UGA, UAG, UAA) for which there is no matching tRNA anticodon (ACU, AUC, AUU) 2.The amino acid chain (protein) is released and the process is complete.

14. Short Quiz 1.What brought each amino acid to the growing protein? The tRNA molecule 2.What determined which tRNA and amino acid would be place in order in the ribosome? The mRNA molecule 3.What determined the mRNA code? The DNA molecule

15. III.DNA and Genes A.What is a gene? A segment of DNA that codes for a protein B. What does a gene start with? An initiation codon (AUG) C.What does a gene end with? A stop codon (UAG, UAA or UGA) D.How many genes are in a DNA molecule? Depends on species, but can be thousands. E.The Central Dogma  DNA is transcribed into RNA, which is then translated into a protein that is expressed as a trait

16. IV.Mutations A.A mutation is any change in an organisms’ DNA B.Point mutations are a change in one or more nucleotides 1.Substitution – replacement of one nucleotide and its complementary partner with another pair of nucleotides

17. 2.Frameshift – addition or deletion of a nucleotide shifts the codons, changing every amino acid that follows the point of mutation Insertion Deletion

19. C.Chromosomal mutations involve a change in the number or structure of chromosome 4 Types: 1.Deletion – loss of all or section of chromosome 2.Duplication – produces extra copies of sections 3.Inversion – reverse the direction of sections 4.Translocation – section breaks off and attaches to another chromosome

20. Deletion Duplication Inversion Translocation DRAW Chromosomal Mutations Figure 12-21, pg 308

21. Chromosome Mutation Movie

22. D.Significance of mutations 1.Most mutations are neutral, but some can result in a beneficial or harmful trait 2.Associated with many types of cancer 3.Source of genetic variability in species