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DNA Replication & Protein Synthesis • The student will investigate and understand common mechanisms of inheritance and protein synthesis. • Key concepts include: – f) the structure, function, and replication of nucleic acids (DNA and RNA); and – g) events involved in the construction of proteins. • • The student will investigate and understand common mechanisms of inheritance and protein synthesis. Key concepts include: – h) use, limitations, and misuse of genetic information; and – i) exploration of the impact of DNA technologies. History • Before the 1940’s scientists didn’t know what material caused inheritance. • They suspected it was either DNA or proteins. History • A series of experiments proved that DNA was the genetic material responsible for inheritance. History • In 1952, Alfred Hershey and Martha Chase did an experiment using a virus that infects E. coli bacteria. • The experiment proved that DNA and not protein is the factor that influences inheritance. History • Erwin Chargaff discovered the base pairing rules and ratios for different species. • Adenine pairs with Thymine • Cytosine pairs with Guanine. History • Rosalind Franklin & Maurice Wilkins had taken the 1st pictures of DNA using X-ray crystallization This proved that DNA had a helical shape. History • The Nobel Prize in Medicine 1962 Francis Harry Compton Crick James Dewey Watson Rosalind Franklin (Died of cancer 1958) Maurice Hugh Frederick Wilkins Watson Crick Wilkins has become a historical footnote and Watson & Crick are remembered as the Fathers of DNA DNA Phosphate Group O O=P-O O Nitrogenous base (A, T, G, C) 5 CH2 O N C4 Sugar C1 (deoxyribose) C3 C2 Nitrogen Bases • 2 types of Nitrogen Bases – Purines PGA • Double ring –G & A – Pyrimidines • Single ring –C & U & T CUT PY DNA - double helix 5 T O A 3 3 P 5 O 5 O C G 1 P 3 2 4 4 2 3 P 1 5 O T 3 P 3 A O P 5 O 5 P DNA • The genetic code is a sequence of DNA nucleotides in the nucleus of cells. DNA • DNA is a doublestranded molecule. • The strands are connected by complementary nucleotide pairs (A-T & C-G) like rungs on a ladder. • The ladder twists to form a double helix. DNA • During S stage in interphase, DNA replicates itself. • DNA replication is a semiconservative process. DNA • Semi-conservative means that you conserve part of the original structure in the new one. • You end up with 2 identical strands of DNA. DNA • Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc.) • A gene is a stretch of DNA. DNA • A mistake in DNA replication is called a mutation. • Many enzymes are involved in finding and repairing mistakes. Mutations • What causes mutations? – Can occur spontaneously – Can be caused by a mutagen • Mutagen: An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism. Mutations • Some mutations can: • Have little to no effect • Be beneficial (produce organisms that are better suited to their environments) • Be deleterious (harmful) Mutations • Types of mutations – Point Mutations or Substitutions: causes the replacement of a single base nucleotide with another nucleotide • Missense- code for a different amino acid • Nonsense- code for a stop, which can shorten the protein • Silent- code for the same amino acid (AA) Mutations • Example: Sickle Cell Anemia Mutations • Types of mutations – Frame Shift Mutations: the number of nucleotides inserted or deleted is not a multiple of three, so that every codon beyond the point of insertion or deletion is read incorrectly during translation. • Ex.: Crohn’s disease Insertion Deletion Mutations • Types of mutations – Chromosomal Inversions: an entire section of DNA is reversed. – Ex.: hemophilia, a bleeding disorder DNA Repair • A complex system of enzymes, active in the G2 stage of interphase, serves as a back up to repair damaged DNA before it is dispersed into new cells during mitosis. RNA Phosphate Group O O=P-O O Nitrogenous base (A, U , G, C ) 5 CH2 O N Sugar (ribose) C4 C3 C1 C2 RNA • Function: obtain information from DNA & synthesizes proteins 3 differences from DNA 1. Single strand instead of double strand 2. Ribose instead of deoxyribose 3. Uracil instead of thymine 3 types of RNA 1. Messenger RNA (mRNA)copies information from DNA for protein synthesis Codon- 3 base pairs that code for a single amino acid. codon 3 types of RNA 2. Transfer RNA (tRNA)collects amino acids for protein synthesis Anticodon-a sequence of 3 bases that are complementary base pairs to a codon in the mRNA 3 types of RNA 3. Ribosomal RNA (rRNA)combines with proteins to form ribosomes Amino Acids • Amino acids- the building blocks of protein • At least one kind of tRNA is present for each of the 20 amino acids used in protein synthesis. Transcription - mRNA is made from DNA & goes to the ribosome Translation - Proteins are made from the message on the mRNA Transcription • In order for cells to make proteins, the DNA code must be transcribed (copied) to mRNA. • The mRNA carries the code from the nucleus to the ribosomes. Translation • At the ribosome, amino acids (AA) are linked together to form specific proteins. • The amino acid sequence is directed by the mRNA molecule. Amino acids ribosome Make A Protein • DNA sequence ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC CAU AUC Make mRNA • mRNA sequence UAC UUU UUG UUC CAU AUC • tRNA sequence AUG AAA AAC AAG GUA UAG Make mRNA • tRNA sequence AUG AAA AAC AAG GUA UAG • Amino Acid sequence met lys asn lys val stop Human Genome Project • The Human Genome Project is a collaborative effort of scientists around the world to map the entire gene sequence of organisms. • This information will be useful in detection, prevention, and treatment of many genetic diseases. DNA Technologies • DNA technologies allow scientists to identify, study, and modify genes. • Forensic identification is an example of the application of DNA technology. Gene Therapy • Gene therapy is a technique for correcting defective genes responsible for disease development. • Possible cures for: – diabetes – cardiovascular disease – cystic fibrosis – Alzheimer's – Parkinson’s – and many other diseases is possible. Genetic Engineering • • The human manipulation of the genetic material of a cell. Recombinant DNA- Genetically engineered DNA prepared by splicing genes from one species into the cells of a different species. Such DNA becomes part of the host's genetic makeup and is replicated. Genetic Engineering • Genetic engineering techniques are used in a variety of industries, in agriculture, in basic research, and in medicine. This genetically engineered cow resists infections of the udders and can help to increase dairy production. Genetic Engineering • There is great potential for the development of useful products through genetic engineering • EX., human growth hormone, insulin, and pestand disease-resistant fruits and vegetables Seedless watermelons are genetically engineered Genetic Engineering • We can now grow new body parts and soon donating blood will be a thing of the past, but will we go too far? Photo of a mouse growing a "human ear"