1 How Proteins Are Made Chapter 10 It has been discovered that each species of organism does NOT have its own unique genetic code for the synthesis of proteins

2 From Genes to Proteins RNA (ribonucleic acid) –Three major differences between DNA and RNA –1. Single stranded –2. Different Sugar – RIBOSE –3. Contains the Nitrogen base (uracil instead of thymine)

3 RNA Nucleotides Sugar – ribose Phosphate Nitrogen base a. Adenine b. URACIL c. Guanine d. Cytosine

4 RNA is chemically similar to DNA except that its sugars have an additional oxygen, and the base thymine is replaced by a structurally similar base called URACIL Remember DNA can NOT leave the nucleus and proteins are made outside of the nucleus at ribosomes

5 Three types of RNA 1. mRNA (messenger RNA- codon) 2. tRNA (transfer RNA –anticodon) 3. rRNA ( ribosomal RNA) Note: RNA polymerase-is the enzyme responsible for making RNA

6 Stages of gene expression 1 st stage – transcription 2 nd stage- translation Cells must control gene expression so that their genes will be expressed or TRNASCRIBED only when the proteins are needed. The portions of DNA molecules that actually code for the production of proteins are called - exons

7 gene expression Introns- interrupters / long segments of nucleotides that have no coding information Many biologists believe that having genes of eukaryotic cells interrupted by introns provides evolutionary flexibility

8 mRNA/Messenger RNA mRNA- is made or produced in the nucleus by a process called transcription The genetic information for making proteins is rewritten as a molecules of messenger RNA During transcription, RNA is produced Transcription is the process by which genetic information encoded in DNA is transferred to a RNA molecule mRNA carries the instructions for making a protein from a gene in DNA to a ribosome in the cytoplasm. (goes from nucleus to cytoplasm)

9 Each nucleotide triplet in mRNA that specifies a particular amino acid is called a codon Remember: messenger RNA- is the form of ribonucleic acid that carries the genetic information from the DNA to the ribosomes Be able to read the codons in mRNA found on page 211. Ex. CUCAAGUGCUUC codes for which amino acids CUC – Leu; AAG-Lys; UGC- CYS; UUC-Phe

10 tRNA/transfer RNA Translation- When Transfer RNA carries a specific ammino acid from the cytoplasm to the complementary mRNA strand on a ribosome. Transfer RNA carries an amino acid to its correct codon In order for translation to occur, mRNA must migrate to the ribosomes

11 Transfer RNA Nucleotide sequences of tRNA that are complementary to codons on mRNA are called anticodons mRNA=CUC AAG UGC UUC tRNA=GAG UUG ACG AAG tRNA=GAG UUG ACG AAG The information contained in a molecule of messenger RNA is used to make proteins during the process of Translation

12 During translation, the amino acid detaches from the transfer RNA molecule and attaches to the end of a growing protein chain when the transfer RNA anticodon bonds to the messenger RNA codon at the ribosome

13 rRNA/ribosomal RNA The function of rRNA is to form ribosomes A ribosome has three binding sites used during translation

14 Be able to interpret the chart on page 211 Be able to form the DNA sequence from mRNA Be able to form the mRNA sequence from DNA and tRNA Given a list of amino acids be able to the correct DNA sequence code. Be able to form tRNA from a mRNA sequence.