Transcription & Translation

Objectives: Relate the concept of the gene to the sequences of nucleotides in DNA Sequence the steps involved in protein synthesis

REMEMBER! A key role of DNA is to make proteins Proteins are assembled by the ribosomes Code of instructions is held in the DNA Code needs to get to the ribosomes, but the DNA cannot leave the nucleus

Genes to Protein The sequence of nucleotides in DNA contain information The information is put to work to make proteins Proteins are key structures and regulators of cell functions ex) walls of blood vessels, filaments in muscle tissue, transport proteins in membranes Enzymes control all chemical reactions of an organism By encoding the instructions for making proteins, DNA controls the cells Proteins are polymers of amino acids

RNA RNA, like DNA, is a nucleic acid. It differs from DNA is 3 ways: RNADNA Double stranded Sugar- deoxyribose Nitrogen Bases: Thymine, guanine, cytosine, and adenine Base Pairing: Adenine - Thymine Cytosine - Guanine Single stranded Sugar- ribose Nitrogen Bases: Uracil, guanine, cytosine, and adenine Base Pairing: Adenine - Uracil Cytosine - Guanine

RNA- role in the cell Job of DNA can be compared to a car assembly line DNA provides the workers with the instructions for making the proteins. The workers build the proteins. Other works bring parts, the amino acids, over to the assembly line.The workers for the assembly line are RNA molecules. They take from the DNA the instructions on how a protein is assembled. They assemble the protein amino acid by connecting amino acid to amino acid

3 types of RNA Type of RNAAbbreviationFunction Messenger RNAmRNABrings message from DNA to cytoplasm and then to ribosomes Ribosomal RNArRNAClamp onto mRNA and use its information to assemble the amino acids in the correct order Transfer RNAtRNATransports amino acids to the ribosomes to be assembled into a protein

Transcription ●How does the information in DNA, which is found in the nucleus (and can not leave the nucleus), move to the ribosomes in the cytoplasm ●Messenger RNA carries the information through the nuclear envelope (the membrane surrounding the nucleus) to the ribosomes ○For manufacturing proteins ●In the nucleus, enzymes make an RNA copy of the portion of the DNA strand in a process called transcription

Transcription Use DNA molecule as a template to make an RNA molecule Thymine is replaced with Uracil

Translation Converts information in a sequence of nitrogen bases in mRNA into a sequence of amino acids that make up a protein Takes place in the ribosomes in the cytoplasm mRNA leaves the nucleus, travels to the cytoplasm, and then becomes attached to the ribosomes

Translation tRNA is responsible for attaching to only one type of amino acid Correct translation of the mRNA molecule relies on the joining of each mRNA codon with the correct tRNA molecule Codon- sequence of 3 nucleotides Anticodon- sequence of 3 nucleotides that are complementary to the codon

Translation 1.Starting end of mRNA becomes attached to the ribosome. Then, tRNA molecules, each carrying a specific amino acid, approach the ribosome 1.Usually the first codon on mRNA is AUG, which signals the start of protein synthesis. When this signal is given, the ribosome slides along the mRNA molecule to the next codon

Translation 3. A new tRNA molecule carrying another amino acid pairs with the second mRNA codon 4.When the first and second amino acids are in place, an enzyme joins them forming a peptide bond 5. As the process continues, a chain of amino acids is formed until the ribosome reaches a stop codon