013368718X_CH15_229-246.indd

Name Class Date Selective BreedingFor Questions 15, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.TRUE 1. Selective breeding works because of the natural genetic variation in a population.DISSIMILAR 2. Hybridization crosses similar individuals to bring together the best of both.HYBRIDS 3. The individuals produced by crossing dissimilar parents are purebreeds.INBREEDING 4. The continued crossing of individuals with similar characteristics is hybridization.TRUE 5. Inbreeding increases the risk of genetic defects.

6. Complete the table describing the types of selective breeding.

Selective BreedingTypeDescriptionExamplesHYBRIDIZATIONCrossing dissimilar individuals to bring together the best of both organismsDISEASE RESISTANT BURBANK POTATOINBREEDINGThe continued breeding of individuals with similar characteristicsELBERTA PEACHES

7. Is it easy for breeders to produce mutants with desirable mutations? Explain.NO, MANY MUTATIONS ARE HARMFUL, AND IT REQUIRED LUCK AND PERSEVERANCE TO PRODUCE A FEW MUTANTS WITH DESIRABLE CHARACTERISTICS THAT ARE NOT FOUND IN THE ORIGINAL POPULATION.8. Why are radiation and chemicals useful techniques for producing mutant bacteria?THE SMALL SIZE OF BACTERIA ENABLES MILLIONS OF ORGANISMS TO BE TREATED AT THE SAME TIME, THUS INCREASING THE CHANCES OF PORDUCING A POWERFUL MUTANT9. What technique do scientists use to produce mutant plants?SCIENTISTS USE DRUGS THAT PREVENT CHROSOMAL SEPARATION DURING MITOSIS10. What are polyploid plants?PLANTS GRWON FROM CELLS THAT HAVE MANY TIMES THE NORMAL CHROMOSOME NUMBER DUE TO THE USE OF DRUGS THAT PREVENT THE SPEARATION OF CHROMOSOMES DURING MITOSIS

Name Class Date

15.2 Recombinant DNACopying DNA Genetic engineers can transfer a gene from one organism to another to achieve a goal, but first, individual genes must be identified and separated from DNA. The original method (used by Douglas Prasher) involved several steps:

Determine the amino acid sequence in a protein.

Predict the mRNA code for that sequence.

Use a complementary base sequence to attract the predicted mRNA.

Find the DNA fragment that binds to the mRNA.Once scientists find a gene, they can use a technique called the polymerase chain reaction to make many copies.

Heat separates the DNA into two strands.

As the DNA cools, primers are added to opposite ends of the strands.

DNA polymerase adds nucleotides between the primers, producing two complementary strands. The process can be repeated as many times as needed.

Changing DNA Recombinant DNA molecules contain DNA from two different sources. Recombinant-DNA technology can change the genetic composition of living organisms.

Plasmids are circular DNA molecules found in bacteria and yeasts; they are widely used by scientists studying recombinant DNA, because DNA joined to a plasmid can be replicated.

A genetic marker is a gene that is used to differentiate a cell that carries a recombinant plasmid from those that do not.

Transgenic Organisms Transgenic organisms contain genes from other species. They result from the insertion of recombinant DNA into the genome of the host organism. A clone is a member of a population of genetically identical cells.

Copying DNAFor Questions 15, complete each statement by writing in the correct word or words.1. Genetic engineers can transfer GENES from one organism to another.2. As a first step toward finding a gene, Douglas Prasher studied the AMINO ACID sequence of part of a protein.3. Prasher next found the mRNA base sequence that coded for the protein.4. Using the technique of GEL ELECTROPHORESIS, Prasher matched the mRNA to a DNA fragment that contained the gene for GFP.5. Southern blot analysis uses RADIOACTIVE probes to bind to fragments with complementary base sequences.

THINK VISUALLY6. Make a sketch to show the steps in the polymerase chain reaction (PCR) method of copying genes. Label each part of your sketch.

Changing DNAFor Questions 710, write the letter of the correct answer on the line at the left.B 7. Why is DNA ligase so important in recombinant DNA technology?A. It causes DNA to make multiple copies of itself.B. It joins two DNA fragments together.C. It shapes bacterial DNA into a circular plasmid.D. It cuts DNA into restriction fragments.D 8. A recombinant plasmid can be used toA. prevent nondisjunction at meiosis.B. double the number of chromosomes in a plant cell.C. cut DNA into restriction fragments.D. transform a bacteriumC 9. What do genetic engineers use to create the sticky ends needed to splice two fragments of DNA together?A. an amino acid sequenceB. DNA ligaseC. restriction enzymesD. mRNAB 10. Why must a genetically engineered plasmid contain a genetic marker?A. to prevent the construction of an artificial chromosomeB. to separate cells that contain recombinant DNA from those that do notC. to produce multiple copies of the recombined plasmid after heat treatmentD. to break apart the circular plasmid and introduce another DNA fragment11. Give a reason why a plasmid is useful for DNA transfer.IT HAS A DNA SEQUENCE THAT HELPS PROMOTE PLASMID REPLICATION; HELPING TO ENSURE THAT THE FOREIGN DNA WILL BE REPLICATED12. What is a transgenic organism?AN ORGANISM THAT CONTAINS GENES FROM OTHER SPECIES13. What can happen when DNA is injected into the nucleus of an animals egg cell?ENZYMES THAT ARE NORMALLY RESPONSIBLE FOR REPAIR AND RECOMBINATION MAY HELP INSERT THE FOREIGN DNA INTO THE CHROMOSOMES OF THE INJECTED CELL14. How is a DNA molecule constructed so that it will eliminate a particular gene?THE TWO ENDS SOMETIMES RECOMBINE WITH SPECIFIC SEQUENCES IN THE HOST CHOROMSOME. THE HOST GENE BETWEEN THE TWO SEQUENCES MAY THEN BE LOST OR REPLACED WITH A NEW GENE15. What is a clone?A MEMBER OF A POPULATION OF GENETICALLY IDENTICAL CELLS PRODUCED FROM A SINGLE CELL16. What kinds of mammals have been cloned in recent years?SHEEP (DOLLY), COWS, PIGS, MICE, AND CATS.

For Questions 1822, write True if the statement is true. If the statement is false, change the underlined word to make the statement true.TRANSGENIC 17. An organism that contains one or more genes from another species is inbred.TRUE 18. Transgenic organisms can be made by inserting recombinant DNA into the genome of the host organism.GENE 19. Examining the properties of a transgenic organism allows scientists to discover the function of the transferred chromosome.TRUE 20. Plant cells will sometimes take up DNA on their own if their cell walls are absent.TRUE 21. Carefully designed DNA molecules can achieve gene replacement.

On the lines below, write T next to an example of a transgenic organism, and C next to an example of a clone.T 22. A goat that produces spiders silk in its milkT 23. A plant that is grown from a cell into which Agrobacterium has incorporated recombinant DNAC 24. A lamb that is born with the same DNA as a donor cellC 25. A colony of bacteria that grows from one bacteriumT 26. A bacterium that can produce human insulin

THINK VISUALLY27. Complete the sentences in the diagram below to show the steps in cloning a sheep.

CELL

NUCLEUS

DIVIDE

EMBRYO

Apply the Big idea

29. The most successful heart transplants occur when proteins in the donor heart closely match those of the recipients original heart. If the proteins dont match, the recipients immune system may reject the transplanted organ. Scientists would like to develop a strain of transgenic pigs that could provide donor hearts for humans. How might such an animal be developed? How might cloning help provide hearts for human recipients?rDNA techniques could be used to splice human genes into the genes of a fertilized egg from a pig. Those genes would direct the developing pig embryo to make a heart similar to a human heart. If the proteins in the pigs heart matched the proteins in a patients original heart closely enough, the pigs heart would not be rejected by the patients immune system. Once such an animal was developed, many hearts might be farmed by cloning the transgenic pig.

Health and MedicineGene Therapy Gene therapy is the process by which genes that cause a disorder are replaced by normal, working genes. Researchers have tried to carry out gene therapy by using viruses to insert the normal DNA into the affected cells. The diagram below shows how a virus might be used to deliver a gene to a bone marrow cell.VirusNormal gene1Chromosomes23NucleusBone marrow cell

Arrange the following steps in the correct order.2Virus infects human cell.1Normal gene is inserted into viral DNA.3Virus delivers its DNA to a human cell.Answer the question.1. Why are viruses used in gene therapy? Viruses have the ability to deliver the desired DNA to the host cell. Viral DNA can enter the DNA of the host organism.Genetic Testing Decide whether each person would benefit from genetic testing. Circle the correct answer.2. Jorge and Ana want to have children. However, Anas brother has hemophilia. Can Ana benefit from genetic testing?yesno3. Juless dad died from influenza. Jules wonders if he will die from the same thing. Can Jules benefit from genetic testing?yesno

Personal IdentificationNo two people are genetically exactly like one another, except for identical twins. DNA fingerprinting is a method used to identify people based on their DNA. DNA fingerprinting has helped solve crimes and convict criminals. It has also helped prove that people are innocent of a crime.Look at the DNA fingerprints below. Then answer the following questions.

1. The DNA fingerprint labeled Evidence was left by a criminal at a crime scene. Police have four different suspects. They took samples of the DNA of each of the four suspects. Which sample matches the evidence? 22. Could sample 1 and sample 2 come from identical twins? Explain your answer. No, the banding patterns in the two samples are different, so the people do not have identical DNA.Decide if the following statements are true or false. If a statement is false, tell why.3. Mitochondrial DNA is passed directly from father to child. False, mitochondrial DNA is passed directly from mother to child.4. DNA evidence can be used to solve crimes, convict criminals, and free people who were wrongfully convicted. True.5. Y-chromosome analysis can be used to determine paternal ancestry in males only.True

6. Complete the flowchart about how DNA fingerprints are made.Restriction enzymes are used to cut the DNA into fragments containing genes and repeats.The restriction fragments are separated according to size using gel electrophoresis.The DNA fragments containing repeats are then labeled using radioactive probes. This labeling produces a series of bandsthe DNA fingerprint.

7. Study the DNA fingerprint below. Which two samples may be from a set of identical twins? How do you know?

Sample 1 and 4 may be from identical twins, they have the same banding pattern.