Page 269 2. How are Punnett squares used? They’re used to predict and compare genetic variations that will result from a cross 4. Define the terms genotype and phenotype A genotype is the genetic makeup of the organism, which may vary with each individual even if they share the same phenotype. The phenotype is the physical characteristics affected by the genotypes. 5. What is the probability that a seed from the cross will produce a tall plant? Use a Punnett square to explain your answer and to compare the probable genetic variations in F2 plants. T Tt
tt
Tt
tt
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t t Probability for tall: 50% Probability for short: 50%. Heterozygous: 50% homozygous tall: 0% homozygous short: 50% Page 274 3. What is the difference between incomplete dominance and codominance? In incomplete dominance the phenotype is somewhere in between the two homozygous phenotypes: red+white=pink. In codominance, both phenotypes are present: red+white=red and white 4. Why are fruit flies an ideal organism for genetic research? Fruit flies are small, easy to keep in the laboratory, and can produce plenty of offspring in a very short amount of time. Page 280 2. What are gene maps, and how are they produced? Gene map-map showing relative locations of each known gene on a particular chromosome. To produce a gene map, find the rate at which linked genes were separated and recombined. Page 283
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7. 3 Page 284 14. State how you would determine the genotype of a white ram A white ram could either have homozygous genes of heterozygous genes. In order to figure out which, the parents and their parents will be needed. If the ram’s parents are a white ram and a black ram, then the ram is heterozygous. If the parents are two white rams, then the genotype could be homozygous or heterozygous. If this is the case then it would be necessary to find the parents’ genotypes in the same way. 15. In rabbits, B is an allele for black coat and b is an allele for brown coat. • •
Write the genotype for a rabbit that is homozygous for black coat BB Write the genotype for a rabbit that is heterozygous for black coat Bb
16. 3 17. 4 18. State one reason it is important to study inheritance of human genetic diseases By studying the inheritance of human genetic diseases scientists can help prevent genetic disorders in the future Page 285 24. Genes that control hair or feather color in some animals are expressed differently in the winter than in the summer. For example, snowshoe hares are white in winter and brown in summer. a. Explain how such a difference in the expression of the gene for fur color might be beneficial to the snowshoe hare A brown hare can blend very well with the trees surrounding it during summer, but in the winter when everything is white, it stands out very much. If its fur turns white then it’ll blend well into the background again. b. Describe how the snowshoe hare’s fur color can change but the genes the animal inherited from its parents do not change The genes might tell the rabbit’s coat color to change, but genes themselves don’t change. It’s merely the phenotype that’s changing.
Page 299 5. What is the role of DNA polymerase in DNA replication? It joins individual nucleotides to produce a DNA molecule, and proofreads each new DNA to make sure each molecule is a perfect copy of the original DNA. Page 306 2. What happens during transcription? RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA 3. What happens during translation? Cell uses information from messenger RNA to produce proteins Page 308 2. What is the significance of mutations to living things? Mutation allows for genetic variation, and in some cases mutations can be very beneficial to the organism and the whole species in general. Page 315 1. 2. 4 3. 4 4. 2 5. 1 6. 4 7. 3 8. 3 9. 4 10.3 11.3 12.1
Page 316 13.Base pairing is an important part of the DNA replication process a. State what is meant by the term base pairing Specific bases can only bond with another specific base. For example, guanine can only bind to cytosine, and adenine can only bond to thymine
b. Explain how base pairing during DNA replication is important in maintaining the genetic code The right number of each base is maintained by base pairing; for every thymine there needs to be an adenine and for every cytosine there has to be a guanine. 15. List the codons of the mRNA molecule that would be transcribed from this strand of DNA. AUG-GGC-UUC-AAG-UAC Methionine-Glycine-Phenylalanine-Lysine-Tyrosine 16. Using Figure 12-17 on page 303, list the sequence of amino acids that this mRNA molecule specifies. Methionine-Glycine-Phenylalanine-Lysine-Tyrosine 17. A template molecule is referred to in the first sentence. Explain what template means. A template is a DNA molecule that acts as a pattern for the synthesis of another molecule of a nucleic acid 18. 3 19. 2 20. In this example, the codon GCA becomes GTA. What is this kind of mutation, which affects only one nucleotide, called? Point mutation 25. After removing the DNA strands from the mixture and allowing them to dry overnight, the students placed them in a test tube cont
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Page 338 12. Describe what a transgenic organism is, and identify three examples of how transgenic bacteria have been used to benefit humans. A transgenic organism is an organism that contains genes from other species. Transgenic bacteria can have been made to create insulin that’s used to cure diabetes. Mice have been modified to have a similar immune system as humans, which allow them to be tested to see what kinds of drugs might cure diseases in humans. Transgenic plants are immune to pesticide, so they can survive when the weeds around them can’t. 15. 2 16. Compare the amount of genetic information in the nucleus of the donor cell with the amount of genetic information in an intact egg cell. All the important genetic information is in the nucleus, because the nucleus has all the genetic information that allows the egg to divide. That’s also why the egg cell does not grow up to look anything like the donor of the egg. 17. Explain why the nucleus of the egg must be removed before using the cells. There isn’t enough genetic information in the original egg. A nucleus from an adult has all 64 chromosomes, but the nucleus of the egg is a gamete, and has only 32 chromosomes. 18. Identify the technique used to separate a mixture of DNA fragments that vary in size. Gel electrophoresis 21. Identify one technique presently being used to alter the genetic makeup of an organism, and explain how humans can benefit from this change. Your answer must include at least: • •
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Name of technique used to alter the genetic makeup Genetic engineering Brief description of what is involved in this technique DNA is extracted from a cell. The DNA is cut so it’s in a form that’s easier to read. Once researchers know enough about the DNA sequence, it can be changed by cutting a piece of DNA away and replacing it with a different DNA from another organism that has different functions. Basically one organism can obtain another organism’s genetics One specific example of how this technique has been used
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Bacteria have been genetically modified before to produce human insulin that is used to treat diabetic patients. A statement of how humans have benefited from the production of this new variety of organism Diabetic patients can have synthetic insulin. People get drugs that were tested on mice with similar human immune systems, and eat food that have been genetically altered to be stronger/immune to pesticides.
Page 348 4. If a woman with type O blood and a man with type AB blood have children, what are the children’s possible genotypes? All their children would have either heterozygous B type blood or heterozygous A type blood. It’s impossible for them to have O or AB blood type. Page 353 1. Why are sex-linked disorders more common in males than in females? Males only have one X chromosome, so all x-linked disorders are expressed in males, even if the allele is recessive Page 360 1. What is the Human Genome Project? It’s an ongoing effort to analyze the human DNA sequence 2. Describe how gene therapy works An absent or faulty gene in a human is replaced by a normal, working gene. Page 363 1. 2. 3. 4. 5. 6. 7. 8. 9.
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Page 364 10.Using one specific example, explain why the human genome project is considered important
The human genome project has mapped a large amount of human genetics. By doing so, someone with a genetic disorder can get gene therapy to help remove the genetic disorder. 11.Explain why scientists must use only certain enzymes when inserting or removing a defective gene from a cell. Different enzymes cut DNA at different locations. If they don’t use a specific enzyme then it will cut away the wrong DNA. 16. Explain how a family pedigree can be helpful in determining the probability of having a child with a genetic disorder. A pedigree has a record of a family’s genetic history of genetic disorders. If a family has a history of having a genetic disorder, researchers can determine if both parents carry the disease, and even if the precise percentile chance of an offspring getting the disease 19. Two prospective parents learn that they each carry one allele for TaySachs disease. •
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Explain why neither of them suffers from Tay-Sachs disease Tay-Sachs must be recessive, so both parents are carrying the disease. Their child might get it, but it’s only a 25% chance If they have children, what are the chances they will have a baby with Tay-Sachs disease? 25% What are the chances that one of their healthy children will carry the Tay-Sachs allele? 50%
Page 365 21. State how scientists actually delivered the missing gene to the eye cells of dogs A virus carried a gene that the blind dogs were missing. This gene is the cause of their blindness. The gene of this virus is delivered into the DNA of the eye cells of the dogs. They did this through surgery. 22. State how scientists demonstrated that gene therapy, and not some other factor, improved the dogs’ ability to see They only treated one eye of each dog, and only the eye that received the gene therapy regained vision.
24. If the gene is successfully inserted and their vision is corrected, will the new gene be passed along to the children of these individuals? Support your answer with an explanation. The new gene will be passed along after the dogs’ visions are corrected, because after the gene is inserted, the sperms/eggs will also begin to contain this gene.