1. Chapter 11.4 One gene=one polypeptide Overview of Protein Synthesis

2. 11.4 One Gene One Polypeptide Each gene codes for a polypeptide (protein). Each gene codes for a polypeptide (protein). A polypeptide is made up of amino acids (monomer) A polypeptide is made up of amino acids (monomer) Proteins can have 1,2,3,or 4 polypeptides, Proteins can have 1,2,3,or 4 polypeptides, Human traits can have more than 1 gene. Human traits can have more than 1 gene. Examples- Examples- 4 genes for eye color. 4 genes for eye color. 3 genes for height. 3 genes for height.

3. The genetic code is universal. What does this mean? What does this mean? It arose very early in the history of life and has been passed on to all living organisms on Earth. It arose very early in the history of life and has been passed on to all living organisms on Earth. All organisms have the same nucleotides- A,C,T,G All organisms have the same nucleotides- A,C,T,G We share 31% of a yeast’s genes, 40% of a worm’s genes, 50% of a fly’s genes. We share 31% of a yeast’s genes, 40% of a worm’s genes, 50% of a fly’s genes.

4. Overview: Information Flows from DNA to RNA to Protein RNA- Ribonucleic Acid- Nucleic Acid- 1, single, twisted strand (chain) of nucleotides. Nucleic Acid- 1, single, twisted strand (chain) of nucleotides. Nucleotide- 3 parts Nucleotide- 3 parts Sugar- ribose Sugar- ribose Phosphate group Phosphate group Nitrogen bases Nitrogen bases Adenine, Guanine, Cytosine, and Uracil- (instead of thymine). Adenine, Guanine, Cytosine, and Uracil- (instead of thymine).

5. Overview of Protein Synthesis- 2 main parts 1.Transcription -nucleus 1.Transcription -nucleus a sequence of DNA nucleotides (a gene) is converted to a single-stranded RNA molecule (mRNA) a sequence of DNA nucleotides (a gene) is converted to a single-stranded RNA molecule (mRNA) mRNA leaves the nucleus to go to the ribosomes. DNA remains in the nucleus. mRNA leaves the nucleus to go to the ribosomes. DNA remains in the nucleus. 2.Translation –ribosomes 2.Translation –ribosomes mRNA is translated into amino acids that combine to form a polypeptide (protein) mRNA is translated into amino acids that combine to form a polypeptide (protein) Codons- three-base nucleotides “words” that code for one amino acid. Codons- three-base nucleotides “words” that code for one amino acid.

6. The Triplet Code There are 20 amino acids. There are 20 amino acids. The A,C,T,G must combine in groups of three to have enough amino acid codes. The A,C,T,G must combine in groups of three to have enough amino acid codes. 4 3 = 64 triplet codes 4 3 = 64 triplet codes 61 of them code for amino acids 61 of them code for amino acids Each codon represents an amino acid. Each codon represents an amino acid. Some amino acids have more than 1 codon- Some amino acids have more than 1 codon- Ex. Leucine can result from CUU, CUC, CUA, CUG. Ex. Leucine can result from CUU, CUC, CUA, CUG. Each codon is specific- CUU is always leucine and not a different amino acid. Each codon is specific- CUU is always leucine and not a different amino acid. 3 “stop” codons which do not code for an amino 3 “stop” codons which do not code for an amino acid. They stop the gene sequence= stops assembling the protein acid. They stop the gene sequence= stops assembling the protein 1 Start codon- AUG= methionine. 1 Start codon- AUG= methionine.