Practice Exam 2 and Answer Key
Practice Exam 2 and Answer Key 30156
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This 12 page Class Notes was uploaded by Hannah Kennedy on Saturday July 30, 2016. The Class Notes belongs to 30156 at Kent State University taught by Dr. Helen Piontkivska in Spring 2016. Since its upload, it has received 54 views. For similar materials see ELEMENTS OF GENETICS in Biological Sciences at Kent State University.
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Date Created: 07/30/16
© Hannah Kennedy, Kent State University Practice Exam 2 Short answer: 1. Explain how gene number and environmental variation affects the overlaps between phenotypes and different genotypes 2. When we say that alleles are additive, what does that mean? 3. What percentage of individuals fall above 2 standard deviations? 4. Is height a discontinuous (i.e. discrete) trait or does it follow a continuum? 5. What are the similarities and differences among natural selection and selective breeding? 6. Humans normally have 2 sets of 23 chromosomes for a total of 46 chromosomes. Individuals with down syndrome have an extra chromosome 21, and thus have 47 chromosomes. How would this chromosomal anomaly be classified? 7. What are the 6 steps in a 3-point mapping procedure 8. Why is it useful to stain chromosomes? 9. Which of the 5 types of changes in chromosome structure (i.e. deletion, duplication, inversion, simple translocation, and reciprocal translocation) alters the total amount of genetic material? 10. What is the reason why a chromosomal fragment is lost and then degraded in a deletion? 11. What is the underlying cause of nonallelic homologous recombination 12. Explain the 2 mechanisms that can cause a reciprocal translocation 13. Which of the mechanisms that cause a reciprocal translocation can be promoted by the presence of the same transposable element in the genome? 14. What adjectives can be used to describe a fruit fly that has a total of 7 chromosomes because it is missing 1 copy of chromosome 3? 15. Describe the imbalance in gene products that would occur in monosomy 2 and trisomy 3 16. Explain why a triploid individual is usually infertile 17. Explain what nondisjunction means 18. What is the key difference between autopolyploidy and allopolyploidy? 19. What type of offspring are found in excess based on Mendel’s law of independent assortment? 20. Why are nonrecombinant offspring more common than recombinant offspring? 21. Does mitotic recombination occur in a gamete or in a somatic cell? 22. Explain ow gene number and environmental variation affects the overlaps between phenotypes and different genotypes Multiple Choice: 1. For quantitative traits, genotypes and phenotypes tend to overlap because… a. The trait changes over time b. They are polygenic c. Environmental variation affects the trait d. Both b and c are correct 2. A QTL is a _______ where 1 or more genes affecting a quantitative trait are _____ a. Site in a cell, located b. Site in a chromosome, located c. Site in a cell, expressed d. Site in a chromosome, expressed 3. To map QTLs, strains are crossed that differ with regard to a. A quantitative trait b. Molecular markers c. A quantitative trait and molecular markers d. A quantitative trait and a discontinuous trait 4. In a population of squirrels in NC, the heritability for body weight is high this means that… a. Body weight is primarily controlled by genes b. Environment has little influence on body weight c. The variation in body weight is mostly due to genetic variation d. Both a and b are correct 5. If 2 or more different genotypes do not respond to environmental variation in the same way, this is an example of… a. A genotype-environment association b. A genotype-environment interaction c. Additive effects of alleles 1 © Hannah Kennedy, Kent State University d. Both a and b 6. One way to estimate narrow-sense heritability for a given trait is to compare _____ for ______. a. Variances, related pairs of individuals b. Correlation coefficients, related pairs of individuals c. Variances, unrelated pairs of individuals d. Correlation coefficients, unrelated pairs of individuals 7. For selective breeding to be successful, the starting population must… a. Have genetic variation that affects the trait of interest b. Be very large c. Be amenable to phenotypic variation caused by environmental effects d. Have very little phenotypic variation 8. The mean weight of cows in a population is 520 kg. Animals with a mean weight of 540 kg are used as parents and produce offspring that have a mean weight of 535 kg. What is the narrow- sense heritability for body weight in this population of cows a. 0.25 b. 0.5 c. 0.75 d. 1 9. A quantitative trait follows a continuum means that a. The trait continuously changes during the life of an individual b. The numerical value for the trait increases with the age of the individual c. Environmental effects are additive d. Phenotypes are continuous and do not fall into discrete categories 10. If 2 or more different genotypes don’t respond to environmental variation in the same way, this is an example of… a. The additive effects of alleles b. A genotype-phenotype association c. A genotype-phenotype interaction d. B and c 11. Which of the following statistics is used to compare 2 variables? a. Correlation b. Standard deviation c. Mean d. Variance 12. Heritability refers to the amount of phenotypic variation that occurs due to… a. Environmental variation b. Monomorphic markers c. Inbreeding d. Genetic variation 13. Which of the following causes an extra copy of a chromosomal region to occur a. Duplication b. Inversion c. Simple translocation d. Reciprocal translocation e. Deletion 14. When a chromosome is broken in 2 places and reconnected so that a region is flipped from the normal order, this is called… a. Deletion b. Reciprocal translocation c. Duplication d. Simple translocation e. Inversion 15. Which of the following occurs when a piece of one chromosome breaks off and is attached to another chromosome? a. Duplication b. Simple translocation c. Reciprocal translocation d. Deletion 2 © Hannah Kennedy, Kent State University e. Inversion 16. Homologous genes are best described as genes that… a. Have a common ancestral gene b. Have identical sequences c. Are on homologous chromosomes d. Have similar functions e. Are on the same chromosome 17. Homologous genes within a single species are said to be a. Xenologs b. Homologs c. Metalogs d. Orthologs e. Paralogs 18. A misaligned cross over between 2 homologous chromosomes usually results in… a. Deletions in both chromosomes b. Duplications in both chromosomes c. A deletion in 1 chromosome and no change in the other d. A deletion in 1 chromosome and a duplication in the other e. No change in either chromosome 19. Genetic duplications are usually caused by… a. Crossing over between non-homologous chromosomes b. Spontaneous insertion of base pairs c. Crossing over between improperly aligned homologous chromosomes d. A chromosome break in one or more places 20. A crossover in 1 region of a chromosome may decrease the likelihood of a second crossover in a nearby region. This phenomenon is called: a. A null mutation b. Coupling c. Mitotic recombination d. Positive interference e. Test crossing 21. A crossover in meiosis is an exchange of genetic material between a. Non-sister chromatids of non-homologous chromosomes b. Sister chromatids of homologous chromosomes c. Non-sister chromatids of homologous chromosomes d. Sister chromatids of non-homologous chromosomes e. Sister chromatids of the same chromosome 22. A tetrad is made up of a. 4 non-homologous chromatids b. 4 non-homologous chromosomes c. 2 homologous chromosomes, each consisting of 2 chromatids d. 4 homologous pairs of chromosomes e. 2 homologous pairs of chromosomes 23. which of the following statements about crossing over is true? a. It occurs only between genes that are heterozygous b. It occurs only in males c. It results in reduced genetic variation among gametes d. It occurs only in some chromosomes e. None of the above y+w yw+ 24. Yyw mated a phenotypically wild-type female of the genotype X X to a male with the genotype X Y. You counted 2205 F 1rogeny and found 17 flies with gray bodies and white eyes and 12 flies that had yellow bodies and red eyes. What is the distance between these genes controlling body color and eye color on the X chromosome? a. 98.7 MU b. 1.32 MU c. 0.78 MU d. 2.63 MU 3 © Hannah Kennedy, Kent State University 25. refer to the cross done in the previous question. If, when counting the1F progeny you didn’t separate the 2 non-recombinant (parental) progeny classes, theoretically, how many of each parental class should be present? a. 1088 b. 29 c. 2176 d. 2205 26. If a gray bodies, red eyed female with genotype Xy+w+Xywwere mated to a wild-type male, which phenotypic class would be counted as a recombinant in the F 1rogeny? a. Yellow bodied females b. White eyed females c. Yellow bodied, white eyed males d. Yellow bodied males 27. Staining eukaryotic chromosomes is useful because it makes it possible to a. Distinguish chromosomes that are similar in size and centromeric locations b. Identify changes in chromosome structure c. Explore evolutionary relationships among diff species d. All of the above 28. A change in chromosome structure that does not involve a change in the total amount of genetic material is a. Deletion b. Duplication c. Inversion d. None of the above 29. Which of the following is correct? a. If a deletion and duplication are the same size, the deletion is more likely to be harmful b. If a deletion and duplication are the same size, the duplication is more likely to be harmful c. If a deletion and duplication are the same size, the likelihood of causing harm is appx the same d. A deletion is always harmful whereas a duplication is always beneficial 30. With regard to gene duplications, which of the following statement(s) is/are correct? a. Gene duplications may be caused by nonallelic homologous recombination b. Large gene duplications are more likely to be harmful than smaller ones c. Gene duplications are responsible for creating gene families that encode proteins with similar and specialized function d. All of the above are correct 31. A paracentric inversion… a. Includes the centromere within the inverted region b. Does not include the centromere within the inverted region c. Has 2 adjacent inverted regions d. Has an inverted region at the very end of the chromosome 32. Due to crossing over within an inversion loop, a heterozygote with a pericentric inversion may produce gametes that… a. Carry a deletion b. Carry a duplication c. Carry a translocation d. Both a and b 33. A mechanism that may cause a translocation is: a. The joining of reactive ends when 2 different chromosomes break b. Crossing over between nonhomologous chromosomes c. Crossing over between homologous chromosomes d. Both a and b 34. In a trisomic individual, such as a person with trisomy 21, a genetic imbalance occurs because a. Genes on chromosome 21 are overexpressed b. Genes on chromosome 21 are underexpressed c. Genes on other chromosomes are overexpressed d. Genes on other chromosomes are underexpressed 4 © Hannah Kennedy, Kent State University 35. Humans that survive with aneuploidy usually have incorrect numbers of chromosome 13, 18, or 21 or the sex chromosomes. A possible explanation why these abnormalities permit survival is because a. The chromosomes have clusters of genes that aid in embryonic growth b. The chromosomes are small and carry relatively few genes c. X inactivation d. Both b and c 36. The term endopolyploidy refers to the phenomenon of having a. Too many chromosomes b. Extra chromosomes inside the cell nucleus c. Certain cells of the body with extra sets of chromosomes d. Extra sets of chromosomes in gametes 37. In agriculture, an advantage of triploid plants is they are a. More fertile b. Often seedless c. Always disease resistant d. All of the above 38. In a diploid species, complete nondisjunction during meiosis I may produce a viable cell that is a. Trisomic b. Haploid c. Diploid d. Triploid 39. The somatic cells of an allotetraploid usually contain a. 1 set of chromosomes from 4 different species b. 2 sets of chromosomes from 2 diff species c. 4 sets of chromosomes from 1 species d. 1 set of chromosomes from 2 diff species 40. genetic linkage occurs because a. genes that are on the same chromosome may affect the same trait b. genes that are close together on the same chromosome tend to be transmitted together to offspring c. genes that are on different chromosomes are independently assorted d. none of the above 41. In the experiment by Bateson and Punnett, which of the following observations suggested linkage in the sweet pea? a. A 9:3:3:1 ratio was observed in F2 b. A 9:3:3:1 ratio was not observed in F2 c. An unusually high number of F2 had phenotypes of the parental generation d. Both b and c 42. With regard to linked genes along the same chromosome, which of the following is false a. Crossing over is needed to produce nonrecombinant offspring b. Crossing over is needed to produce recombinant offspring c. Crossing over is more likely to separate alleles if they are far apart on the same chromosome d. Crossing over that separates linked alleles happens during prophase I 43. Morgan observed a higher number of recombinant offspring involving eye color and wing length than recombinants for body color and eye color. This happened because a. The genes affecting eye color and wing length are farther apart on the X chromosome than are the genes affecting body color and eye color b. The genes affecting eye color and wing length are closer together on the X chromosome than are the genes affecting body color and eye color c. The gene affecting wing length isn’t on the X chromosome d. The gene affecting body color is not on the X chromosome 44. In a chi square analysis involving genes that may be linked, which of the following is correct a. An independent assortment hypothesis is not proposed because the data usually suggests linkage b. An independent assortment hypothesis is proposed because it allows you to calculate expected numbers of offspring 5 © Hannah Kennedy, Kent State University c. A large chi square value suggests that the observed and expected data are in good agreement d. The hypothesis is rejected when the chi square value is low 45. The process of mitotic recombination involves the a. Exchange of chromosomal regions between homologs during gamete formation b. Exchange of chromosomal regions between homologs during the division of somatic cells c. Reassortment of alleles that occurs at fertilization d. Reassortment of alleles that occurs during gamete formation 46. Which of the following is an example of a quantitative trait a. Height b. Rate of glucose metabolism c. Ability to learn a maze d. All of the above 47. Saying that a quantitative trait follows a continuum mean that a. The numerical value for the trait increases with the age of the individual b. Environmental effects are additive c. Phenotypes are continuous and don’t fall into discrete categories d. The trait continuously changes during the life of an individual 48. The variance is a. A measure of the variation around the mean b. Computed as a squared deviation c. Higher when there is less phenotypic variation d. Both a and b 49. Which of the following statistics is used to compare two variables a. Mean b. Correlation c. Variance d. Standard deviation Fill in the blank 1. Quantitative traits, such as height and weight, are viewed as _________--traits that don’t fall into discrete categories 2. A certain threshold must be reached in which the number of disease-causing alleles results in the development of the disease. These are referred to as _______--traits that are inherited quantitatively due to the contribution of many genes, but the traits themselves are expressed qualitatively 3. Some quantitative traits, such as bristle number in Drosophilia, are _______--traits that can be counted and expressed in whole numbers 4. The term _________ refers to the transmission of a trait governed by 2 or more different genes 5. The location on a chromosome that harbors 1 or more genes that affect the outcome of a quantitative trait is a called a __________ 6. The basis of ________ is the association between genetically determined phenotypes for quantitative traits and molecular markers such as RFLPs, microsatellites, and single-nucleotide polymorphisms (SNPs) 7. ________ inversions do not include the centromere 8. ________ inversions do include the centromere 9. _______ occurs when a segment of the chromosomal material is missing 10. _______ occurs when a segment of the chromosome is repeated when compared to the parent 11. _______ involves a change in direction of the genetic material along a chromosome 12. ___________ occurs when a single piece of chromosome is attached to a different chromosome 13. ___________ occurs when 2 different chromosome exchange pieces producing 2 abnormal chromosomes with translocations 14. an organism that has a chromosome number that is an exact multiple of a chromosome set is ________ 15. an organism with 2 sets of chromosomes (2n) is ________ 16. an organism with 3 sets of chromosomes (3n) is ________ 6 © Hannah Kennedy, Kent State University 17. an organism with an alteration in the number of particular chromosomes, so the total number of chromosomes is not an exact multiple of a set is ________ 18. an organism with 1 extra chromosome (2n+1) is _______ 19. an organism with 1 less chromosome (2n-1) is _______ 20. a diagram that depicts the sequence of genes along a chromosome is called a ______ 21. 2 or more genes that are located on the same chromosome are _______ 22. when genes that are close together on the same chromosome are transmitted as a unit it is called ___________ 23. an entire chromosome is considered a ____________, as it contains a group of genes that are physically linked together 24. in each species, the number of linkage groups equals the ________ number of chromosome types 25. a crossover within a pericentric inversion results in ________ or ________ chromosomes 26. a crossover within a paracentric inversion results in an _______ fragment of a ________ chromosome 27. variation in the number of chromosomes may involve changes in the number of sets, known as _______ 28. variation in the number of chromosomes may also involve changes in the number of particular chromosomes within a set, known as __________ 29. _____________ refers to the phenomenon in which the number of DCOs in a given region is less than expected based on the frequencies of SCOs True or False 1. A chromosomal mutation is a substantial change in the structure of a chromosome(s) 2. Both inversions and translocation can lead to overall deficiencies and duplications of genetic material after meiosis 3. An individual carrying one copy of a normal chromosome and one copy of an inverted chromosome is known as an inversion heterozygote 4. Inversion heterozygotes are often phenotypically normal and have a low probability of producing gametes that are abnormal in their total genetic content 5. In order for an inversion heterozygote to undergo crossing over, an inversion loop must form so that the homologous genes on both chromosomes align next to each other despite the inverted sequence 6. A crossover is more likely to occur in an inverted region if the chromosome segment with the inversion is small 7. A crossover involving a paracentric inversion produces a dicentric chromosome 8. Gene duplications have no effect on evolution 9. Homologous genes are the result of random mutations accumulated over the course of many generations 10. Crossing over occurs during prophase I of meiosis 11. Crossing over allows the reassortment of linked genes 12. A genetic map allows geneticists to understand the overall complexity and genetic organization of a particular species 13. Knowing the locus of a gene within a genetic map can help molecular geneticists clone the gene 14. Genetic maps can be used to improve our understanding of the evolutionary relationships among species 15. Genetic maps can be used to diagnose and treat inherited human diseases 16. Genetic counselors can use genetic maps to determine if an individual will express a particular gene 17. Genetic maps provide plant and animal breeders with helpful information for improving agriculturally important strains through selective breeding programs Matching 1. Math the following mechanisms that produce variation in chromosome number with the phenotypic result Mechanism: Variation: 1. Meiotic nondisjunction a. Allopolyploidy 2. Mitotic nondisjunction b. Aneuploidy or polyploidy 3. Interspecies crosses c. mosaicism 7 © Hannah Kennedy, Kent State University 8 © Hannah Kennedy, Kent State University Practice Exam 2 Answers Short answer 1. As gene number increases and environmental effects on the genes get stronger, the overlaps between phenotypes and different genotypes increases, making it more difficult to differentiate between the two 2. 3. 4. Continuum 5. Primary difference is due to how the parents are chosen. So, in natural selection they’re chosen via natural variation in reproductive success but in selective breeding, the breeder chooses the individuals that possess traits that are desirable from a human perspective. They are similar because they are related due to Darwin discussing being influenced by his observation of selective breeding of pigeons. 6. Aneuploidy, trisomy 7. (1): cross 2 true-breeding strains with 3 different alleles. (2): perform a testcross by mating the F1 female heterozygotes to males. (3): collect data for the F2 generation. (4): determine which offspring are recombinant: recombinant offspring are due to crossing over in the heterozygous female parent. (5): calculate the map distance between pairs of genes. Repeat for all recombinant genes. (6): construct the map 8. to distinguish between similar-looking chromosomes, to identify changes in chromosome structure, and to explore evolutionary relationships among diff species 9. deletions and duplications 10.if a chromosomal fragment doesn’t contain a centromere, it will not segregate properly. If it remains outside of the nucleus then it will be degraded 11.nonallelic homologous recombination occurs due to the pairing of homologous site that duplicated on the chromosome (known as repetitive sequences) the pairing of them causes the chromosomes to be misaligned 12.(1): when 2 different chromosomes break, DNA repair enzymes attempt to put the pieces back together. However, if 2 different chromosomes break at the same time, the incorrect ends can be put on one another. (2): a crossover between nonhomologous chromosomes 13.If transposable elements are found within the genome, nonhomologous chromosomal crossover may occur by promoting the pairing of nonhomologous chromosomes 14.Aneuploidy, monosomic, monosomy 3 15.In monosomy 2, the gene products are only found in 1 copy when compared to a euploid number of chromosomes in the other sets, where they’re found in 2 copies. The gene expression of these genes would there for be less at appx 50% expression than compared to the other copies, thus creating an imbalance. Moreover, in trisomy 3, the genes are found in 3 copies when compared to a euploid number of chromosomes in the other sets. The gene expression would thus be more at appx 150%, creating another imbalance. 16.A triploid individual is usually infertile because during meiosis, the homologs cannot align in a balanced way, giving rise to aneuploid gametes, which are most often nonviable 17.Nondisjunction means that pairs of chromosomes are not separating properly 18.In autopolyploidy, multiple sets of chromosomes come from the same species. However, in allopolyploidy, multiple sets of chromosomes come from at least 2 different species 19.The offspring that resemble their parental phenotypes 20.This is because linked genes are usually close together so a crossover is unlikely between them, resulting in less recombinant offspring 21.Somatic cells 22.As the number of genes increase and the environmental variation increases, there is a greater phenotypic overlap 1 © Hannah Kennedy, Kent State University Multiple Choice 1. D 2. B 3. C 4. C 5. B 6. B 7. A 8. C 9. D 10.C 11.A 12.D 13.A 14.E 15.B 16.A 17.E 18.D 19.C 20.D 21.C 22.C 23.E 24.B 25.A 26.D 27.D 28.C 29.A 30.D 31.B 32.D 33.D 34.A 35.D 36.C 37.B 38.C 39.B 40.B 41.D 42.A 43.A 44.B 45.B 46.D 47.C 48.D 49.B 2 © Hannah Kennedy, Kent State University Fill in the blank 1. Continuous traits 2. Threshold traits 3. Meristic traits 4. Polygenic inheritance 5. Quantitative trait locus (QTL) 6. QTL mapping 7. Paracentric 8. Pericentric 9. Deletion 10.Duplication 11.Inversion 12.Simple translocation 13.Reciprocal translocation 14.Euploid 15.Diploid 16.Triploid 17.Aneuploi 18.Trisomic 19.Monosomic 20.Genetic map 21.Syntenic 22.Genetic linkage 23.Linkage group 24.Haploid 25.Duplicated, deleted 26.Acentric, dicentric 27.Euploidy 28.Aneuploidy 29.Positive interference True or false 1. True 2. True 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10.True 11.True 12.True 13.True 14.True 15.True 16.False 17.True Matching 1. 1 → b, 2 → c, 3 → a 3 © Hannah Kennedy, Kent State University 4
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