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1 DNA • DNA is often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell. 2 Watson & Crick’s Model 3 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 Why do we study DNA? We study DNA for many reasons, e.g., • its central importance to all life on Earth, • medical benefits such as cures for diseases, • better food crops. 9 Chromosomes and DNA • Our genes are on our chromosomes. • Chromosomes are made up of a chemical called DNA. 10 The Shape of the Molecule • DNA is a very long polymer. • The basic shape is like a twisted ladder or zipper. • This is called a double helix. 11 The Double Helix Molecule • The DNA double helix has two strands twisted together. 12 One Strand of DNA • The backbone or sides of the ladder of the molecule are alternating phosphates and deoxyribose sugar • The teeth or rungs of the ladder are nitrogenous bases. phosphate deoxyribose bases 13 Nucleotides One deoxyribose together with its phosphate and nitrogen base make a nucleotide. O O -P O Nitrogenous base O O Phosphate C C O C Deoxyribose 14 Nucleotides O O -P O O O O -P O One deoxyribose together with its phosphate and base make a nucleotide. O O O -P O Nitrogenous base O O Phosphate C C O C Deoxyribose 15 One Strand of DNA nucleotide • One strand of DNA is a polymer of nucleotides. • One strand of DNA has many millions of nucleotides. 16 Four nitrogenous bases DNA has four different bases: • Cytosine C • Thymine T • Adenine A • Guanine G 17 Two Stranded DNA • Remember, DNA has two strands that fit together something like a zipper. • The teeth are the nitrogenous bases but why do they stick together? 18 C N N C N N C C C O • The bases attract each other because of hydrogen bonds. • Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. • The bonds between cytosine and guanine are shown here with dotted lines N Hydrogen Bonds N C N C C O 19 C N Hydrogen Bonds, cont. • When making hydrogen bonds, cytosine always pairs up with guanine • Adenine always pairs up with thymine • Adenine is bonded to thymine here O N O C C C C N C 20 Chargaff’s Rule: Base Pairing Rule • Adenine and Thymine always join together A T • Cytosine and Guanine always join together C G 21 DNA by the Numbers • Each cell has about 2 m of DNA. • The average human has 75 trillion cells. • The average human has enough DNA to go from the earth to the sun more than 400 times. • DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun. 22 What have we learned about DNA so far? • 1. DNA is made of units called _________. • 2. A sugar and a _______ make up the sides of the DNA ladder? • 3. DNA is found in the ____ of a eukaryotic cell. • 4. If a one strand of DNA is: ATCCGTAAG. What is the complementary strand? • 5. What three scientists won the Nobel prize in medicine for their discovery of DNA’s structure? • 6. What is the process where viruses reproduce called? What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a _______ make up the sides of the DNA ladder? What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a __phosphate_ make up the sides of the DNA ladder? • 3. DNA is found in the ____ of a eukaryotic cell. What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a __phosphate_ make up the sides of the DNA ladder? • 3. DNA is found in the _nucleus_ of a eukaryotic cell. • 4. If a one strand of DNA is: ATCCGTAAG. What is the complementary strand? What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a __phosphate_ make up the sides of the DNA ladder? • 3. DNA is found in the _nucleus_ of a eukaryotic cell. • 4. If a one strand of DNA is: ATCCGTAAG. What is the complementary strand? TAGGCATTC • 5. What three scientists won the Nobel prize in medicine for their discovery of DNA’s structure? What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a __phosphate_ make up the sides of the DNA ladder? • 3. DNA is found in the _nucleus_ of a eukaryotic cell. • 4. If a one strand of DNA is: ATCCGTAAG. What is the complementary strand? TAGGCATTC • 5. What three scientists won the Nobel prize in medicine for their discovery of DNA’s structure? Watson, Crick and Wilkins • 6. What is the process where viruses reproduce called? What have we learned about DNA so far? • 1. DNA is made of units called __nucleotides__. • 2. A sugar and a __phosphate_ make up the sides of the DNA ladder? • 3. DNA is found in the _nucleus_ of a eukaryotic cell. • 4. If a one strand of DNA is: ATCCGTAAG. What is the complementary strand? TAGGCATTC • 5. What three scientists won the Nobel prize in medicine for their discovery of DNA’s structure? Watson, Crick and Wilkins • 6. What is the process where viruses reproduce called? The Lytic Cycle 30 RNA & Protein Synthesis © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved Chromosome Structure of Eukaryotes Nucleosome Chromosome DNA double helix Coils Supercoils Histones Nucleosomes pack together to form thick coiled fibers. When cell is NOT dividing, these fibers are spread out in nucleus as CHROMATIN (Allows reading of code) ___________. Image from: http://evolution.berkeley.edu/evosite/evo101/images/dna_bases.gif HOW IS DNA COPIED? The structure of DNA explains how it can be copied. Each strand has all the info needed to construct matching the __________other half. If strands are separated, base-pairing rules allow _____________ you to fill in the complementary bases. Figure 12–11 DNA Replication Section 12-2 New strand Original strand DNA polymerase Growth DNA polymerase Growth Replication fork Replication fork New strand Original strand Nitrogenous bases Sites where strand separation and replication forks replication occur are called _____________ REPLICATION STEPS 1.Enzymes “unzip” molecule by breaking _______________ Hydrogen bonds that hold the strands together and unwind it. DNA polymerase joins nucleotides 2. _______________ using original strand as template and spell checks ______________for errors. opposite directions 3. Copying happens in ________ along the two strands & in __________ multiple places at once. DNA Replication • DNA replication occurs before every cell in the body divides. • Every cell in the body has the exact same DNA (except for sex cells) • Replication occurs in the S stage of the Interphase part of cell division or (Mitosis) REPLICATION ANIMATION See a video clip about DNA REPLICATION (12B) ACTIVITY • BE A DNA MOLECULE 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. Replication Quiz A---? G---? C---? 2. When does replication occur? T---? 3. Describe how replication works. A---? G---? A---? 4. Use the complementary rule to G---? create the complementary C---? strand: A---? G---? T---? 1. Why is replication necessary? Replication Quiz 1. Why is replication necessary? So both new cells will have the correct DNA 2. When does replication occur? 3. Describe how replication works. 4. Use the complementary rule to create the complementary strand: A--G--C--T--A--G--A--G--C--A--G--T--- Replication Quiz 1. Why is replication necessary? So both new cells will have the correct DNA 2. When does replication occur? During interphase (S phase). 3. Describe how replication works. 4. Use the complementary rule to create the complementary strand: A--G--C--T--A--G--A--G--C--A--G--T--- Replication Quiz A---T 1. Why is replication necessary? G---C So both new cells will have the correct C---G DNA T---A 2. When does replication occur? A---T During interphase (S phase). G---C 3. Describe how replication works. A---T Enzymes unzip DNA and complementary G---C nucleotides join each original strand. C---G 4. Use the complementary rule to A---T create the complementary strand: G---C T---A 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. • 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. (Almost anything that you can think of that causes cancer is a mutagen.) Mutations • A change in DNA sequence • A mistake that’s made during replication, translation, transcription or cell division • Can be: harmful: disease deformities helpful: organism better able to survive neutral: organism unaffected If a mutation occurs in a sperm or egg cell, that mutation is passed to the offspring, if a mutation occurs in a body or somatic cell it only affect the organism and is not passed on to the offspring. Mutations • Example: Sickle Cell Anemia When can having the sickle cell trait be an advantage? Mutations • Example: Hemophilia 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. Occurs in the nucleus 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 mRNA ---Transcription DNA RNA • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence ???? Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC CAU Make mRNA ---Transcription • DNA sequence • ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC CAU AUC Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) ___ ____ ____ ____ ____ ____ Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG GUA Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG GUA UAG Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG GUA Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG GUA Make a Protein • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC tRNA sequence (anti- codon) AUG AAA AAC AAG GUA Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Leu Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Leu Phe Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Leu Phe Hist Make Protein (amino acids) • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Leu Phe Hist Iso Make mRNA • mRNA sequence (codon) UAC UUU UUG UUC CAU AUC Tyr Phe Leu Phe Hist Iso Amino Acid sequence --- Protein 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" 1. Why is transcription necessary? 2. 3. 4. 5. Describe transcription. Why is translation necessary? Describe translation What are the main differences between DNA and RNA? 6. Using the chart on page 211, identify the amino acids coded for by these codons: UGGCAGUGC 1. Why is transcription necessary? 2. 3. 4. 5. 6. Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm. Describe transcription. Why is translation necessary? Describe translation What are the main differences between DNA and RNA? Using the chart on page 211, identify the amino acids coded for by these codons: UGGCAGUGC 1. Why is transcription necessary? Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm. 2. Describe transcription. RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA. 3. Why is translation necessary? 4. Describe translation. 5. What are the main differences between DNA and RNA? 1. Why is transcription necessary? Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm. 2. Describe transcription. RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA. 3. Why is translation necessary? DNA cannot leave the nucleus, so mRNA carries the message. 4. Describe translation. 4. Describe translation. The cell uses information from MRNA to produce proteins. 5. What are the main differences between DNA and RNA. 6. Using the codon chart, identify the amino acids coded for by these codons: UGGCAGUGC 4. Describe translation. The cell uses information from MRNA to produce proteins. 5. What are the main differences between DNA and RNA. DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil. 6. Using the codon chart, identify the amino acids coded for by these codons: UGGCAGUGC 4. Describe translation. The cell uses information from MRNA to produce proteins. 5. What are the main differences between DNA and RNA. DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil. 6. Using the codon chart, identify the amino acids coded for by these codons: UGGCAGUGC tryptophan-glutamine-cysteine If a strand of DNA is 30% Adenine, then what percentage of the cell is: Thymine – Guanine- Cytosine - DNA strand A G T A T G T T G T A A G C T Replicate DNA DNA Replicate DNA strand strand DNA T G A A T G A C C T C A G T A C C G T A G C A G C T T A G C Replicate DNA