* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 3 - Cell Protein Production
Histone acetylation and deacetylation wikipedia , lookup
Protein moonlighting wikipedia , lookup
Promoter (genetics) wikipedia , lookup
RNA interference wikipedia , lookup
Western blot wikipedia , lookup
Gene regulatory network wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Non-coding DNA wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Bottromycin wikipedia , lookup
Molecular evolution wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Protein adsorption wikipedia , lookup
Polyadenylation wikipedia , lookup
Protein (nutrient) wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Proteolysis wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Protein structure prediction wikipedia , lookup
List of types of proteins wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Point mutation wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Non-coding RNA wikipedia , lookup
Biochemistry wikipedia , lookup
Transfer RNA wikipedia , lookup
Gene expression wikipedia , lookup
Expanded genetic code wikipedia , lookup
Genetic code wikipedia , lookup
Cell Protein Production Chapter 3 © 2010 McGraw-Hill Australia To learn about the stages of protein synthesis click on the stage names in blue. Transcription Protein Formation Summary Translation © 2010 McGraw-Hill Australia Transcription • Transcription is the process by which the mRNA is formed using the code in a DNA molecule • The genetic instructions are copied (or transcribed) from the DNA to the mRNA molecule • The enzyme RNA polymerase begins the process of making mRNA © 2010 McGraw-Hill Australia Transcription (cont.) • RNA polymerase makes the double-stranded DNA molecule come apart, usually about 17 base pairs at a time • RNA polymerase then transcribes (copies) the bases on one strand of the DNA to make a complementary molecule of mRNA © 2010 McGraw-Hill Australia Transcription (cont.) • RNA molecules have the base uracil (U) instead of thymine • At the end of the gene there is a sequence of bases that tells the RNA poly-merase to stop copying and as a consequence the mRNA molecule is released © 2010 McGraw-Hill Australia Transcription (cont.) • The strand that is copied is called the template strand because it is the template from which the mRNA is made. The other strand is known as the coding strand • Not all of the bases in the DNA molecule are code for an amino acid. The noncoding sequences are called introns © 2010 McGraw-Hill Australia Transcription (cont.) • The base sequences that code for amino acids are called exons • The functional mRNA will leave the nucleus and direct protein synthesis in the cytoplasm Return © 2010 McGraw-Hill Australia Translation • Translation is the production of a protein using the information that is coded in the mRNA molecule • In the cytoplasm a ribosome attaches to one end of the mRNA molecule. using a sequence that is the binding site for the ribosome © 2010 McGraw-Hill Australia Translation (cont.) • The ribosome then moves along the mRNA three bases at a time, reading the bases as it goes • When the ribosome reaches the start codon (AUG) it starts making the protein Return © 2010 McGraw-Hill Australia Protein Formation • Transfer RNA (tRNA) bring the individual amino acids to the ribosome to be joined together as proteins • Each tRNA molecule has a section that binds to its corresponding amino acid © 2010 McGraw-Hill Australia Protein Formation (cont.) • The loop of the tRNA has three nitrogen bases that form an anticodon. These three bases bind with the complementary bases of a codon on the mRNA molecule • The anticodon determines the type of amino acid carried by the tRNA © 2010 McGraw-Hill Australia Protein Formation (cont.) • As the ribosome reads the codons on the mRNA, tRNA molecules with the matching anticodon are brought in • The amino acids carried by the tRNA are joined together so the protein is assembled with the amino acids in the correct sequence © 2010 McGraw-Hill Australia Protein Formation (cont.) • Once the tRNA has delivered its amino acid it detaches from the ribosome and can pick up another amino acid from the cytoplasm • One mRNA often has 10 or 20 ribosomes reading its code at the same time • This means that a cell could produce over 150 000 protein molecules per second Return © 2010 McGraw-Hill Australia Summary • Each gene in the DNA in the cell nucleus carries the code for making a protein from amino acids Transcription • The two strands of the DNA in a gene separate • mRNA forms with bases that are complementary to those on the template strand of the DNA • The mRNA molecule that is formed undergoes modification – the introns are removed leaving just the exons • mRNA travels from the nucleus to the cytoplasm Translation • mRNA attaches to a ribosome • The ribosome moves along the mRNA reading the code. At the start codon it begins making the protein • For each codon on the mRNA, a tRNA with a matching anticodon brings the correct amino acid • The amino acids are bonded together to form the protein © 2010 McGraw-Hill Australia