UNIT SIX: MOLECULAR GENETICS AND BIOTECHNOLOGY

Transcription

1 UNIT SIX: MOLECULAR GENETICS AND BIOTECHNOLOGY MAIN IDEA: THE DISCOVERY THAT DNA IS THE GENETIC CODE INVOLVED MANY EXPERIMENTS OBJECTIVE 1: EXPLAIN THE IMPORTANCE OF DNA, ANALYZE ITS STRUCTURE, AND DESCRIBE THE IMPORTANCE OF NUCLEOTIDE SEQUENCES A. Genetic material held in the molecules of DNA ultimately determines an organism s traits. 1. DNA achieves this control by making all the proteins for an organism. a. Remember enzymes are proteins and these control the chemical reactions needed for life.. B. Review structure of DNA 1. made of structural units called nucleotides a. sugar deoxyribose b. Phosphate one phosphorous atom surrounded by 4 oxygen atoms c. Nitrogen base a carbon ring that contains one or more atoms of nitrogen. There are four bases: adenine (A), guanine (G), cytosine (C), and thymine (T), so DNA has four possible nucleotides. d. Nucleotides form long chains, with the phosphate group of one nucleotide bonding to the deoxyribose sugar of the adjacent nucleotide. e. The amount of adenine always equals the amount of thymine, and the amount of cytosine is always equal to the amount of guanine: Chargoff s rule (see page 329, Figure 12.5) C. Four scientists joined the search for the DNA structure: Franklin, Wilkins, Crick and Watson 1. Rosalind Franklind s Photo and x-ray diffraction data helped Watson and Crick solve the structure of DNA. The photo indicated that DNA was a double helix a twisted ladder shape 2. Watson and Crick proposed the double helix structure of DNA (see page 331 figure 12.8): a. Two outside strands of alternating deoxyribose and phosphate b. Cytosine and guanine bases pair to each other by three hydrogen bonds. c. Thymine and adenine bases pair to each other by two hydrogen bonds. 3. Two strands of DNA running antipparallel make up the DNA helix. a. Carbon molecules can be numbered in organic molecules like sugar. b. On the top the 5 carbon is on the left and on the end of the rail the 3 is on the right. The strand is oriented 5 to 3 c. The strand on the bottom is oriented 3 to In 1953, Watson and Crick published a one page letter suggesting the structure of DNA and hypothesized a method for its replication. In the same issue, Franlkin and Wilkins presented evidence supporting Watson and Crick. 5. The variation found among species is because of the varying sequence of the four different nucleotides along the DNA strands. OBJECTIVE 2: DESCRIBE THE BASIC STRUCTURE OF A EUKARYOTIC CHROMOSOME A. (See Page 332, Figure 12.9) Eukaryote DNA is organized into chromosomes each having from 51 million to 245 million base pairs. B. In order to fit into the eukaryotic cell, the DNA tightly coils around a group of beadlike proteins called histones. C. The phosphate groups in DNA create a negative charge, which attract the DNA to the positively charged histone proteins and form a nucleosome. The nucleosomes then group together into chromatin fibers, which supercoil to make up the DNA structure recognized as a chromosome. MAIN IDEA: DNA REPLICATES BY MAKING A STRAND THAT IS COMPLIMENTARY TO EACH ORIGINAL STRAND. OBJECTIVE 3: DESCRIBE THE REPLICATION OF A DNA MOLECULE AND THE ROLE OF ENZYMES IN THE REPLICATION PROCESS A. Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes in interphase. The DNA in the chromosomes is copied in a process called semiconservative replication. 1. Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA. (see pages 333 and 334) 2. Without DNA replication, new cells would have only half of the DNA of their parents; species could not survive and individuals would not grow or reproduce successfully. 3. ALL organisms undergo DNA replication. 1

2 B. Many enzymes are needed to ensure proper DNA replication 1. DNA helicase is the enzyme responsible for unwinding and unzipping the double helix. This enzyme helps break the hydrogen bonds that hold the two strands of DNA together. 2. Single stranded binding proteins associate with the DNA and keep the strands separate during replication. 3. As the helix unwinds, another enzyme, RNA primase, adds a short segment of RNA called RNA primer on each strand of DNA. 4. The enzyme DNA polymerase adds new nucleotides to the 3 end of the new strand. a. adenine bonds with thymine and cytosine bonds with guanine C. Now the genetic make-up of an organism can be passed on to new cells during mitosis or to new generations through meiosis followed by sexual reproduction. OBJECTIVE 4: EXPLAIN HOW LEADING AND LAGGING STRANDS ARE SYNTHESIZED DIFFERENTLY A. When completing semiconservative replication, the two strands of DNA are made in a slightly different manner. B. One strand is called the leading strand and is elongated as the DNA unwinds. 1. It is built continuously with nucleotides added to the 3 end. C. The lagging strand elongates away from the replication fork. 1. It is synthesized discontinuously into small fragments called Okazaki fragments by the DNA polymerase in the 3 to 5 direction. 2. An enzyme called DNA ligase will later connect these fragments. D. So, not only is DNA replication called semiconservative but is also called semidiscontinuous. E. Their may be many areas along the chromosome where replication began. When DNA polymerase comes to an RNA primer on the DNA, it removes the primer and fills in the place with DNA nucleotides. When the RNA polymerase has been replaced, DNA ligase links the two sections. OBJECTIVE 5: COMPARE DNA REPLICATION IN EUKARYOTES AND PROKARYOTES A. Eukaryotic DNA unwinds in multiple areas as DNA is replicated. 1. Each individual area of a chromosome replicates as a section, so multiple areas of replication are occurring along the large eukaryotic chromosome at the same time. (see page 335, figure 12.12) B. In prokaryotes, the circular DNA strand is opened at one origin of replication. (see page 335, figure 12.12) 1. Replication occurs in two directions just as in eukaryotic replication. 2. DNA replication is shorter than in eukaryotics and it remains in the cytoplasm, not packaged into the nucleus. MAIN IDEA: DNA CODES FOR RNA, WHICH GUIDES PROTEIN SYNTHESIS OBJECTIVE 6: DESCRIBE HOW GENES ARE RELATED TO PROTEINS A. Sequences of DNA contain information to produce proteins. B. Review the structure and function of proteins. Enzymes (a type of protein) control all the chemical reactions in an organism. C. By encoding the instructions for making proteins, DNA controls cells. D. The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein. Each human cell contains about 80, 000 genes. E. Geneticists now accept the basic mechanism for reading and expressing genes is from DNA to RNA to protein. OBJECTIVE 7: DESCRIBE THE STRUCTURE AND FUNCTION OF RNA A. RNA (ribonucleic acid) is a nucleic acid and its structure is similar to that of DNA. 1. RNA is single stranded, with alternating chains of phosphate and sugar. 2. The sugar is ribose. 3. The nitrogen bases are adenine, guanine, cytosine, and uracil. Uracil pairs with adenine. THERE IS NO THYMINE IN RNA! B. RNA takes instruction from DNA and assembles the protein amino acid by amino acid. C. There are three structural types of RNA that help to build proteins. (see page 336, table 12.2) 1. Messenger RNA (mrna) molecules are long strands of RNA nucleotides that are formed complimentary to one strand of DNA. They travel to the nucleus to the ribosome to direct the synthesis of a specific protein. 2

3 2. Ribosomal RNA (rrna) this type of RNA is associated with proteins to form ribosomes in the cytoplasm 3. Transfer RNA (trna) smaller segments of RNA that transport amino acids to the ribosome. OBJECTIVE 8: DESCRIBE THE PROCESSES OF TRANSCRIPTION AND TRANSLATION A. Transcription: DNA à mrna (see page 337) 1. DNA unzips, but only one side of the DNA acts as a template 2. RNA polymerase, an enzyme that regulates RNA synthesis, binds to a specific site where RNA will be made. 3. As DNA unwinds, the RNA polymerase starts RNA synthesis along one strand of DNA in a 3 to 5 direction. a. The strand that is read by RNA polymerase is called the template strand and RNA nucleotides are added to the 3 end 4. The complimentary nucleotide will bind temporarily to the DNA strand, acting as a template, so that the information from the DNA is now transcribed to form mrna a. if the DNA base is G then the RNA base is C b. if the DNA base is C then then RNA base is G c. if the DNA base is T then the RNA base is A d. if the DNA base is A then the RNA base is U 5. When the correct sequence of complimentary bases has been transcribed, the mrna detaches from the DNA 6. While in the nucleus, the RNA is modified. Introns (sequences of nucleotides that don t carry useful information for protein synthesis) are cut out and spliced together at exons, the coding sequences that remain in the final mrna. Once processed the mrna carries the appropriate codon sequence for protein and leaves the nucleus and enters the cytoplasm. 1. Other processing strategies of the pre-mrna include adding a protective cap at the 5 end (thought to aid in ribosome recognition) and adding a tail of many adenine nucleotides called a poly-a tail (function presently unknown) 7. The DNA strands zip back together. 8. Instructions for protein synthesis are encoded in DNA. The only way DNA varied among organisms is in the sequence of nitrogenous bases. 1. Twenty amino acids are used to make proteins, so DNA must provide for at least 20 different codes. 2. Based on math, it was hypothesized that a group of three bases coded for a single amino acid. 64 combinations are possible when a sequence of three bases is used; thus 64 different mrna codons are in the genetic code. 3. The code for protein synthesis, therefore is the order of the bases in a single strand of DNA. Every three bases on mrna (or every three nucleotides) are known as a codon and codes for one amino acid. (see page 338 Fig. 12.4) a. Some codons do not code for amino acids; they may be stop codons. B. Translation: mrna à trna à protein (see pages 339) a. Once mrna is synthesized and processed it moves out of the nucleus to the ribosome in the cytoplasm. b. The 5 end of the mrna attaches to rrna (the ribosome), the workbench for protein synthesis c. There are many different types of trna and this molecule acts as as the interpreters of the mrna codon sequence. 1. Each trna carries a specific amino acid on its head. 2. Each trna has as series of three bases at its feet called an anticodon. 3. If a codon on the mrna were CGA then the complimentary anticodon would be GCU. 4. The anticodon is read 3 to 5 d. The first complimentary trna lands on the mrna and passes its amino acid to the second trna e. The third trna receives the two amino acids from the second trna. f. A start codon signals the beginning of the sequence of codons to be translated and stop codons end the sequence to be translated to a protein. Eventually a long chain of amino acids is formed which is the protein. g. Depending on the complexity of the organism, there may be 100 to several 1000 proteins as part of its makeup. 3

4 h. Each of the 20 amino acids can appear many times in the protein molecule. The structure and function of each protein depends on the sequence of amino acids. i. All organisms use the same genetic code for amino acids and assembling proteins. j. These proteins become enzymes and cell and tissue structures. The formation of protein, originating from the DNA code, produces the diversity of our living world! MAIN IDEA: GENE EXPRESSION IS REGULATED BY THE CELL, AND MUTATIONS AFFECT THIS EXPRESSION OBJECTIVE 9: DESCRIBE HOW BACTERIA (PROKARYOTES) ARE ABLE TO REGULATE THEIR GENES BY TWO TYPES OF OPERONS A. Gene regulation is the ability of an organism to control which genes are transcribed in response to the environment. B. In prokaryotes, an operon, often controls the transcription of genes in response to changes in the environment. 1. An operon is a section of DNA that has genes for the proteins needed for a specific metabolic pathway. a. Parts of an operon are an operator, promoter, regulatory gene, and genes coding for proteins. C. The operator is a piece of DNA that acts as an on/off switch for transcription. D. A 2 nd segment of DNA is called the promoter where the RNA polymerase first binds to DNA. E. The trp operon is a repressible operon (see page 343, figure 12.7) 1. Synthesis of the amino acid tryptophan occurs in five steps and each step is catalyzed by an enzyme. 2. The five genes coding for these enzymes are clustered together on the chromosome 3. Transcription of the five enzymes is normally repressed, or turned off. If tryptophan is in the environment then the prokaryote doesn t need to make it so the trp repressor gene turns off the transcription process by making a repressor protein. 4. Tryptophan combines with the inactive repressor protein and this complex binds to the operator in the promoter sequence. With the repressor bound to the operator, RNA polymerase cannot bind to it, which prevents the transcription of the enzyme genes. This stops the synthesis of tryptophan by the cell. F. The lac operon is an example of the gene expression of inducible enzymes. (see page 343, figure 12.18) It is an inducible operon because transcription is turned on by an inducer. 1. Bacteria make an enzyme that let use lactose as an energy source. 2. The lactose operon contains a promoter, an operator, a regulatory gene, and three enzymes that control lac digestion. 3. When the lac operon is off, the regulatory gene makes a repressor protein that binds to the operator in the in the promoter sequence and prevents the transcription of the enzyme genes. 4. When the inducer is present, it binds to the repressor and inactivates it. The inducer is allactose, a molecule that is present in foods that have lactose. SSSOOOO, when lactose is present, the allactose binds to the repressor and inactivates it. With the repressor inactivated, RNA polymerase can bind to the promoter and start transcription. OBJECTIVE 10: DISCUSS HOW EUKARYOTIC REGULATE TRANSCRIPTION OF A GENE A. In eukaryotic cells, many genes interact with one another, requiring more than one promoter and operator for a set of genes. B. One way that eukaryotes control gene expression is through proteins called transcription factors. 1. Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amount. 2. There are two main sets of transcription factors: a. One factor forms complexes that guide and stabilize the binding of the RNA polymerase to the a promoter. b. Another set includes regulatory proteins that help control the rate of transcription. C. The shape of eukaryotic DNA also regulates transcription. Because eukaryotic DNA is wrapped around histones to form nucleosomes, this structure provides some inhibition of transcription. 1. Some regulatory proteins and RNA polymerase still can activate specific genes even if they are packaged in the nucleosome. D. Gene regulation is VERY important during development. As the zygote undergoes mitosis, it produces all kinds of cells needed by the organism. During differentiation the cells will become specialized. 4

5 1. Genes called Homeobox (hox) control differentiation. 2. Hox genes determine the body plan of an organism. 3. Hox genes code for transcription factors and are active zones of the embryo that are in the same order as the genes on the chromosome. (see page 344, figure 12.19) a. These genes, transcribed at specific times, and located in specific places on the genome, control what body part will develop in a given location. E. RNA interference (RNAi) is another way eukaryotes regulate genes. 1. An enzyme called dicer cuts small pieces of double stranded RNA. These small pieces are called small interfering RNA. 2. The small interfering RNA binds to a protein complex that degrades one strand of RNA, preventing its translation. 3. The use of RNAi as a genetic therapy to silence a specific gene that has gone bad has entered human therapeutic clinical trials. OBJECTIVE 11: DEFINE THE WORD MUTATION AND DIFFERENTIATE BETWEEN VARIOUS TYPES A. Any change in the DNA sequence is called a mutation. The mutation may or may not effect the expression of the gene or the sequence of amino acids in the encoded protein. B. A point mutation is a change in a single base pair in DNA. A single change in a single nitrogen base can change the entire structure of the protein because a change in a single amino acid can affect the shape of the protein. It is enough to cause a genetic disorder. Types of point mutations include the following: 1. Substitution one base is exchanged for another a. missense substitutions code for the wrong amino acid b. nonsense substitutions change the codon for an amino acid to a stop codon. These cause translation to stop early. Nearly all of these make proteins that are nonfunctional. c. The change of one amino acid for another amino acid in a protein can affect the folding and stability of the protein. (see page 347, figure 12.22) This is the cause of sickle cell disease, in which the structure of hemoglobin is changed. C. A frameshift mutation occurs when a single base is added or deleted from DNA causing a change in the chromosome structure. 1. Insertions gain of a nucleotide 2. Deletion loss of a nucleotide 3. This would cause nearly every amino acid in the protein after the deletion or addition to be changed. D. In general, point mutations are less harmful to an organism than a frameshift mutation because they disrupt only a single codon. E. Sometimes mutations are associated with diseases and disorders. (See page 346, Table 12.3) F. Large portions of DNA can also be involved in a mutation and have drastic effects on the expression of these genes. 1. A piece of an individual chromosome containing one or more genes can be deleted or moved to a different location on the chromosome or even to a different chromosome a. Inversions occur when part of a chromosome breaks off and is reinserted backwards. b. Translocations occur when part of one chromosome breaks off and is added to a different (non-homologous) chromosome. G. In 1991, a new kind of mutation was discovered that involves an increase in the number of copies repeated codons, called tandem repeats. 1. Fragile X syndrome is due to many repeated CGG units near the end of the X chromosome, making the lower tip of the X chromosome appear fragile. (see page 347, Figure 12.21) H. Some mutations result from a change in the number of chromosomes (review unit 4) 1. Changes in numbers result in monosomy, trisomy, and polyploidy. 2. Few chromosomes mutations are passed on to the next generation because the zygote usually dies. In cases where the zygote survives, the mature organism is usually sterile and incapable of producing offspring. 3. Nondisjunction is a type of chromosome mutation that occurs frequently in plants and can be beneficial. 5

6 OBJECTIVE 12: DESCRIBE CAUSES OF MUTATIONS AND EXPLAIN HOW DNA CAN REPAIR ITSELF A. Some mutations are spontaneous they just happen, especially point mutations 1. During replication, DNA polymerase may add the wrong nucleotides, but because DNA polymerase has a proofreading mechanism, the wrong nucleotide gets added only for one in 100,000 bases; it goes unfixed in less than 1 in 1,000,000, The greater the exposure to the mutagen, the more likely the chance that a mistake will not be corrected. B. Many mutations are caused by factors in the environment. 1. Any agent that can cause a change in DNA is called a mutagen. 2. Mutagens include high-energy radiation, chemicals, and even high temperatures. C. Many chemicals are mutagens and have a variety of affects. Chemical mutagens may be found in the environment or in building materials: dioxin, asbestos, benzene, cyanide, and formaldehyde. 1. Some chemical mutagens have chemical structures that look like nucleotides so closely that they substitute for them. If they become part of DNA it can replicate properly. a. Medically this type of chemical has become useful: many drugs used to treat HIV mimic various nucleotides. Once incorporated into the viral DNA, the DNA cannot copy itself. 2. Some affect DNA by changing the chemical structure of the bases. Bases may misrepair or bond with wrong bases. D. Forms of radiation, x-rays, cosmic rays, and nuclear radiation are highly mutagenic. 1. When radiation reaches the DNA, electrons absorb energy and may escape from their atom, leaving behind what is called a free radical. Free radicals are charged atoms with unpaired electrons that react violently with other molecules, including DNA. 2. U.V. radiation does not create free radicals but can cause adjacent thymine bases to bind to one another, causing a disruption or kink in the DNA and preventing the replication of the DNA. OBJECTIVE 13: DIFFERENTIATE BETWEEN A BODY CELL AND A SEX CELL MUTATION A. If the mutation in a body cell (somatic cell) escapes the repair mechanism, it can be passed on to the daughter cell. This does not affect future generations. 1. Some mutations might be neutral and might not cause problems to the cell if: a. the mutation is in a sequence that is not used by the adult cell b. the mutation occurred in an exon c. the mutation may have not changed the amino acid coded for. 2. Some mutations may result in the production of an abnormal protein, causing inability for cell function or even cell death. 3. If the mutation affects the cell cycle, the result can be cancer. B. When mutations occur in the sex cells, also called sperm line cells, the mutations are passed on to the organism s offspring. 1. These mutations might not affect the function of the cell in the organism, but DRAMATICALLY affect the offspring. MAIN IDEA; RESEARCHERS USE GENETIC ENGINEERING TO MANIPULATE DNA OBJECTIVE 14: EXPLAIN THE CONCEPT OF GENETIC ENGINEERING AND DISCUSS THE TOOLS USED TO ENGINEER TRANSGENIC ORGANISMS A. Genetic engineering involves cutting DNA from one organism into small fragments and inserting the fragments into a host organism of the same or different species. 1. Also called recombinant DNA technology (connecting or recombining DNA fragments from different sources). 2. Recombinant DNA technology involves the recombination of specific pieces of DNA, in the lab, between pre-selected organisms to achieve a specific goal. The scientist, rather than natural selection, then determines the usefulness of the recombinant DNA. 3. Can be used to quickly and reliably increase the frequency of a specific allele in a population, much faster than selective breeding. 4. Genetically engineered organisms are used to study the expression of a specific gene, investigate cellular processes, study the development of a certain disease, and select traits that might be beneficial to people. B. An organism s genome is the total DNA present in the nucleus of each cell. Genomes can contain millions and millions of nucleotides in the DNA within genes. 6

7 C. DNA tools can be used to manipulate DNA and to isolate genes from the rest of the genome. 1. Fragments of DNA are cut (digested) from a larger chromosome using restriction enzymes bacterial proteins that can cut both strands of the DNA molecule at specific nucleotide sequences. a. Restriction enzymes are also called endonucleases and are used by bacteria for defense against viruses. b. Eco RI is is a restriction enzyme used by scientists to cut DNA at a specific site GAATTC. c. Now the double stranded DNA has single-stranded ends which attract other single stranded ends. The ends are sticky. d. If the same enzyme is used to cut DNA from two organisms, the two pieces of DNA will have matching sticky ends and will join or recombine. (see page 364, Figure 13.4) 2. Gel electrophoresis is used to separate DNA fragments according to their size by using an electric current. (see page 365, Figure 13.5) a. Form little gel squares with holes (wells) in one end b. Place some of the cut pieces of DNA in one of the wells that are negatively charged c. Submerge the gel under water d. Add electricity to the water e. The DNA fragments move to the positive end of the gel, sorting themselves according to size. Larger pieces with more base sequences move the least distance. f. The unique pattern created based on size of the DNA fragment can be compared to known DNA fragments for identification. OBJECTIVE 15: EXPLAIN HOW RECOMBINANT DNA IS MADE AND THEN USED IN GENE CLONING, DNA SEQUENCING, AND POLYMERASE CHAIN REACTION A. When DNA fragments have been separated by gel electrophoresis, fragments of a specific size can be removed from the gel and combined with DNA fragments from another source. This newly generated DNA molecule with DNA from different sources is called recombinant DNA. This enables individual genes to be studied. B. Many steps are used in forming recombinant DNA and large quantities of molecules are needed in order to study it. 1. First, carriers called vectors transfer the recombinant DNA into the bacterial cell called the host cell. Vectors can be biological (viruses or rings of DNA from bacteria called plasmids ) or they can be mechanical. Host cells can also be a plant or animal. a. Plasmids (a ring of DNA) are useful because they can be cut with restriction enzymes. 2. Gene splicing or ligation rejoins the DNA fragments. (see page 366, Figure 13.6) a. If a plasmid and a DNA fragment from another genome have been cleaved by the same restriction enzyme, their ends will be complimentary and can be combined. b. An enzyme normally used by cells in DNA repair and replication, called DNA ligase, joins the two DNA fragments chemically. C. The recombinant DNA can now be inserted into s host cell so that lots of the recombinant DNA can be made. D. Large numbers of identical bacteria, each containing the inserted recombinant DNA, can be made in a process called cloning. 1. To make a large quantity of recombinant plasmid DNA, bacterial cells are mixed with recombinant DNA. Some bacterial cells take up the recombinant plasmid DNA through a process called transformation. (See page 367, Figure 13.7) a. When heated temporary openings in the plasma membrane allow recombinant DNA plasmid to enter the bacterial cell. The bacterial cells make copies of the recombinant plasmid DNA during replication. E. DNA can be sequenced to provide scientists with much information: 1. Used to predict the gene s function 2. Enables scientists to compare the genes with similar sequences from other organisms 3. Enables scientists to identify mutations or errors in the DNA sequence a. before sequencing the DNA must be digested using restriction enzymes 4. See page 368 to understand how DNA is sequenced F. Polymerase chain reaction (PCR) can be used to make millions of copies of a specific region of a DNA fragment, once the DNA has been sequenced. 1. PCR is used for research in laboratories, by forensic scientists to identify suspects and victims in criminal investigations, and by doctors studying and detecting infectious diseases. G. See page 370, Table 13.1 to review tools/ process, function and application of genetic engineering. 7

8 OBJECTIVE 16: DEFINE BIOTECHNOLOGY AND DESCRIBE HOW TRANSGENIC ORGANISMS MAY BE BENEFICIAL A. Biotechnology, the use of genetic engineering to find solutions to problems, makes it possible tpp produce organisms that contain individual genes from other organisms. 1. Organisms that have been genetically engineered by inserting genes from another organism are called transgenic organisms. B. Transgenic organisms are used in research and include bacteria, plants and animals. 1. Transgenic animals a. most are made in the lab for research, often to study diseases and how to treat them. Mice, fruit flies and roundworms are commonly used. b. Livestock have been produced to improve the food supply and human health. Transgenic goats have been engineered to secrete a protein, antithrombin III, which is used to prevent human blood from clotting during surgery. c. Transgenic fish have been produced to grow faster. 2. Transgenic plants a. Many species have been developed to be resistant to insect and viral pests. b. Researchers are developing peanuts and soybeans that don t cause allergic reactions. c. Many types are foods that would improve the human condition: (1) sweet potato plants that would withstand a virus that typically wipes out most of the African harvest (2) rice with increased iron and vitamins that could decrease malnutrition in Asia (3) bananas that produce vaccines for infectious diseases (4) plants that produce biodegradable plastics C. Transgenic bacteria 1. Insulin growth hormones, and substances that dissolve blood clots are made by transgenic bacteria. 2. Other transgenic bacteria prevent frost damage on crops, clean up oil spills, and decompose garbage. MAIN IDEA: GENOMES CONTAINALL OF THE INFORMATIONNEEDED FOR AN ORGANISM TO GROW AND SURVIVE OBJECTIVE 17: DESCRIBE COMPONENTS OF THE HUMAN GENOME A. A genome is the complete genetic information of a cell. The Human Genome Project (HGP) was an international project that was completed in 2003 and its goal was to 1. determine the sequence of the approximately 3 billion nucleotides that make up human DNA 2. identify all of the 20,000 to 50,000 human genes. B. Scientists have studied the genome of other organisms as a way to help develop the technology needed to handle the large amounts of data generated by the HGP. Technologies help interpret the function of newly identified genes. C. In order to determine one continuous human genome sequence, each of the 46 human chromosomes was cleaved. 1. Restriction enzymes cut the DNA with overlapping sequences, then the fragments are combined with vectors making recombinant DNA, which is then cloned and sequenced using an automated sequencing machine. 2. DNA sequencing can be used to identify defective genes by sequencing the DNA of people with a specific disease and comparing the sequence who do not have the disease. D. After sequencing the genome, scientists found that less than 2% of all the nucleotides in the human genome code for all the proteins in the body. 1. The genome must be filled with long stretches of repeated sequences that have no direct function. These are called noncoding sequences. OBJECTIVE 18: DESCRIBE HOW FORENSIC SCIENTISTS USE DNA FINGERPRINTING A. The long, noncoding sequences of DNA are unique to each individual. So when these regions are cut by restriction enzymes, the set of DNA fragments that are made are unique to the individual too. B. DNA fingerprinting involves separating these DNA fragments using gel electrophoresis in order to observe the distinct banding patterns that are unique to each person. C. DNA fingerprinting can be used to identify suspects and victims in criminal cases, determine paternity, and identify soldiers killed in war. 8

9 1. Genetic information can be obtained from blood, hair, semen and skin. 2. PCR is used to copy small amounts of DNA. DNA is then digested using restriction enzymes. DNA fragments are then separated by gel electrophoresis and compared to DNA fragments of known sources such as victims an suspects. D. Since its development in 1985, DNA fingerprinting has also been used to exonerate those wrongfully convicted E. Pharmacogenomics 1. Pharmacogenomics is the study of how genetic inheritance affects the body s response to drugs. Benefits include more accurate dosing of drugs that are safer and more specific. 2. Might allow for drugs to be custom-made for a specific individual based on their genetic makeup. 3. Prescribing drugs based on someone s individual makeup will increase safety, speed recovery and decrease side effects. F. Gene Therapy 1. This is a technique aimed at correcting mutated genes that cause human diseases. 2. Scientists insert a normal gene into a chromosome to take the place of a dysfunctional gene. 3. In most cases, a normal gene is fused with a viral vector to create recombinant DNA. Target cells in the patient are infected with the virus and the recombinant DNA material is released into the affected cells. 4. Once in the normal cells the gene inserts itself into the patients genome and starts functioning. 5. In 2003 the FDA stopped gene therapy trials in the U.S. after the death of a patient caused by a reaction to the viral vector. 9