DNA & Protein Synthesis The source and the process!
Agenda I. DNA and Genes II. Protein Synthesis III. The Genetic Code
I. DNA & Genes: The beauty of DNA Remember: DNA is a macromolecule that stores information what IS that information? Instructions for building all structures for all living things where in the molecule is it stored? the information is IN the sequence of base pairs Why are we different from a fly or a flower or bacteria?
I. DNA & Genes: What is a gene? A specific sequence of DNA that codes for a specific protein Alternate versions of a gene for the same trait are called alleles ex: trait is eye color; alleles are green or blue ex: trait is blood type; alleles are A, B or O
I. DNA & Genes: Not all DNA codes for protein Introns There are non-coding regions occur both between and within genes called introns In humans, genes make up only 5% of all DNA (!!)
I. DNA & Genes: The Human Genome Project Chromosome Genes Total base pairs Sequenced base pairs Cumulative (%) 1 2,000 247,199,719 224,999,719 7.9 2 1,300 242,751,149 237,712,649 16.2 3 1,000 199,446,827 194,704,827 23.0 4 1,000 191,263,063 187,297,063 29.6 5 900 180,837,866 177,702,766 35.8 6 1,000 170,896,993 167,273,993 41.6 7 900 158,821,424 154,952,424 47.1 8 700 146,274,826 142,612,826 52.0 9 800 140,442,298 120,312,298 56.3 10 700 135,374,737 131,624,737 60.9 11 1,300 134,452,384 131,130,853 65.4 12 1,100 132,289,534 130,303,534 70.0 13 300 114,127,980 95,559,980 73.4 14 800 106,360,585 88,290,585 76.4 15 600 100,338,915 81,341,915 79.3 16 800 88,822,254 78,884,754 82.0 17 1,200 78,654,742 77,800,220 84.8 18 200 76,117,153 74,656,155 87.4 19 1,500 63,806,651 55,785,651 89.3 20 500 62,435,965 59,505,254 91.4 21 200 46,944,323 34,171,998 92.6 22 500 49,528,953 34,893,953 93.8 X (sex chromosome) 800 154,913,754 151,058,754 99.1 Y (sex chromosome) 50 57,741,652 25,121,652 100.0 Total 20,000 to 25,000 3,079,843,747 2,857,698,560 100.0 The Human Genome Project (HGP) was the international, collaborative research program whose goal was the complete mapping and understanding of all the genes of human beings. All our genes together are known as our "genome." Upon publication of the majority of the genome in February 2001, Francis Collins, the director of NHGRI, noted that the genome could be thought of in terms of a book with multiple uses: "It's a history book - a narrative of the journey of our species through time. It's a shop manual, with an incredibly detailed blueprint for building every human cell. And it's a transformative textbook of medicine, with insights that will give health care providers immense new powers to treat, prevent and cure disease."
I. DNA & Genes: How does DNA determine the way living things look? Inherited DNA specifies traits by directing synthesis of proteins these proteins then form or direct the formation of structures which then relate to an organisms physical appearance In other words: proteins are the link between our genetic make up (genotype) and our physical appearance (phenotype)
II. Protein Synthesis: DNA directed protein synthesis Transcription making RNA from DNA takes place in the nucleus Translation making protein from RNA takes place outside of the nucleus on ribosomes these may be in the cytoplasm freely, or attached to the cells endoplasmic reticulum
II. Protein Synthesis: Transcription the details Initiation an enzyme (RNA polymerase) attaches to the promoter, a start here site on DNA indicating the start of a gene Elongation RNA polymerase builds a copy of the gene (the transcript) which gets longer and longer this gene copy is called messenger RNA or just mrna Termination enzyme reaches the terminator ( stop here ) at the end of a gene and detaches from the DNA the mrna is a free-floating single stranded copy of a gene Capping & editing (mrna processing) ends of mrna are protected (cap and tail) & non-coding parts are removed (splicing) now the mrna can leave the nucleus
II. Protein Synthesis: Transcription of a gene
II. Protein Synthesis: The Basics Transcription making RNA from DNA takes place in the nucleus Translation making protein from RNA takes place outside of the nucleus on ribosomes these may be in the cytoplasm freely, or attached to the cells endoplasmic reticulum
II. Protein Synthesis: Translation the basics 1. mrna and trna come together at the ribosome = initiation 2. trna brings the an amino acid based on the mrna codon (the 3 mrna bases that code for a specific amino acid) = elongation 3. The amino acids attach together to form a protein, and according to the directions will be released = termination
II. Protein Synthesis: Translation the details Step 1: Initiation 1 st - the small ribosomal unit binds to the mrna 2 nd - a special trna recognizes start codon on mrna & binds to it with amino acid 3rd the large ribosomal unit binds to the group, forming the initiation complex
II. Protein Synthesis: Translation the details Step 2: Elongation the next codon specifies which amino acid-carrying trna (if it is carrying a trna it is called charged ) will bind to it ribosome facilitates the binding between the amino acids, the shifting of the mrna and release of the discharged trna.
II. Protein Synthesis: Translation the details Step 3: Termination 1 st the ribosome complex reaches a stop codon & a release factor binds to the stop codon 2 nd this releases the polypeptide and the trna 3 rd all units dissociate for reuse, including the mrna
II. Protein Synthesis: What happens next (to the polypeptide)? The finished polypeptide chain is modified = posttranslational modification 1. the chain of polypeptides = Primary Protein Structure 2. the chain then forms folds and helices = Secondary Protein Structure 3. then the folds & helices fold on and around each other = Tertiary Protein Structure 4. multiple tertiary proteins can join = Quaternary Protein Structure
III. The genetic code The link between the codons in RNA & the amino acids of proteins Redundancy without ambiguity This language is shared by all living things bacteria can transcribe human DNA & human cells can translate bacterial mrna
A Quick Big Picture Review