BioSci 110, Fall 08 Exam 2

Transcription

1 1. is the cell division process that results in the production of a. mitosis; 2 gametes b. meiosis; 2 gametes c. meiosis; 2 somatic (body) cells d. mitosis; 4 somatic (body) cells e. *meiosis; 4 gametes 2. A 21-year old male MSU student is sunbathing in Fort Lauderdale during Spring Break. As a result of excessive UV radiation, a mutation (change in base sequence) occurs in the Y chromosome in a skin cell on his shoulder. The mutated chromosome: a. will be passed on to all of his children b. will be passed on to all of his sons, but none of his daughters c. will be passed on to all of his sons, and half of his daughters d. will be passed on to half his sons, but none of his daughters e. *will not be passed on to any of his children 3. The locus for a gene of interest is marked on the chromosome figures below. At meiosis 1, a crossing-over event occurs in which the long-arms are exchanged between homologous chromosomes. For which chromosome(s) will the crossing-over have no effect on the resulting genotypes of the gametes? a.* b. c. d. B and C e. All of the above will result in changed genotypes of gametes 4. Hemophilia is a genetic disorder that results in excessive bleeding due to absence of an important clotting factor. Hemophilia is inherited as an X-linked recessive allele. If a woman with hemophilia marries a normal man, what outcome do you expect for their children? Girls Boys a* 100% girls are carriers 100% are hemophiliacs b 100% girls are normal 100% are hemophiliacs c 50% girls are carriers; 50% are hemophiliacs 50% are normal, 50% are hemophiliacs d 50% girls are carriers; 50% are normal 50% are normal, 50% are hemophiliacs e 50% girls are carrier; 50% are hemophiliacs 50% are carriers, 50% are hemophiliacs (Questions 5 and 6). Squash color is controlled by the interaction of two epistatic genes. White squash (W) is dominant to colored squash (w). If this gene is homozygous recessive, a second gene (Y) controls squash color where yellow (Y) is dominant to green (y). 5. Which genotype results in yellow squash? a. WWyy b. WwYY c. WwYy d. *wwyy e. wwyy 6. At market, yellow squash sells better than white or green. If a farmer knows that she has seeds with the genotype WwYy, what would be the best genotype to cross her seeds with to maximize yellow squash production (and profit)? a. WWyy b. *wwyy c. wwyy d. WWYY 1

2 (Questions 7-10) The Canary Islands are seven islands just west of the African continent. The islands gradually became colonized with life: plants, lizards, birds, etc. Three different species of lizards found on the islands are similar to one species found on the African continent (Thorpe and Brown 1989). Because of this, scientists assume that the lizards traveled from Africa to the Canary Islands by floating on tree trunks washed out to sea. 7. On one of the islands, a well-established population of lizards is made up of hundreds of individual lizards. The lizards in the lizard population are likely to be: a. indistinguishable, since there is a lot of interbreeding in isolated populations. b. the same genotypically, but display differences in their phenotypes. c. the same phenotypically, but display differences in their genotypes. d. *similar, yet have some significant differences in their genotypes and phenotypes. 8. Which statement best describes how traits in lizards will be inherited by offspring? a. When parent lizards learn to catch particular insects, their offspring can inherit their specific insectcatching skills. b. When parent lizards develop stronger claws through repeated use in catching insects, their offspring can inherit their stronger-claw trait. c. When parent lizards claws are underdeveloped because easy food sources are available, their offspring can inherit their weakened claws. d. *When a parent lizard is born with an extra finger on its claws, its offspring can inherit six-fingered claws. 9. According to the theory of natural selection, where did the variations in body size in the three species of lizards most likely come from? a. The lizards needed to change in order to survive, so beneficial new traits developed. b. The lizards wanted to become different in size, so beneficial new traits gradually appeared in the population. c. *Random genetic changes and sexual recombination both created new variations. d. The island environment caused genetic changes in the lizards. 10. Fitness is a term often used by biologists to explain the evolutionary success of certain organisms. Below are descriptions of four fictional female lizards. Which lizard might a biologist consider to be the most fit? Lizard A *Lizard B Lizard C Lizard D Body length 20 cm 12 cm 10 cm 15 cm Offspring surviving to adulthood Age at death 4 years 5 years 4 years 6 years Comments Lizard A is very healthy, strong, and clever Lizard B has mated with many lizards Lizard C is darkcolored and very quick Lizard D has the largest territory of all the lizards (Questions 11 and 12). In cats, ear shape and hair length are independently controlled by genes carried on separate chromosomes (they are not linked). Short hair (H) is dominant to long hair (h), and curled ears (E) are dominant to straight ears (e). Moses (from Exam 1) has short hair and straight ears. Moses mother has long hair and curled ears. 2

3 NAME: KEY PID: Group#/Name: 11. (16 pts) In the panels below, draw cells from Moses at the phases indicated. Draw the correct number of cells and chromosomes in each panel and label: alleles (B, b, E, e) homologous chromosomes (1 pt) centromere (1 pt) sister chromatids (1 pt) a. (2 pts) What is Moses genotype? Hhee (1 pt Hh; 1 pt ee) b. (3 pts) Moses cell at G2 (after DNA replication) A correct representation includes: 4 chromosomes correctly labeled with alleles chromosomes are in the replicated state, sisters are identical correct genotype (from above) is represented c. (2 pts) Moses cell/s at metaphase of meiosis 1. chromosomes are in the replicated state, and lined up in pairs at the equatorial plane homologous chromosomes are opposite one another at the equatorial plane d. (3 pts) Moses cell/s at metaphase of meiosis 2. 2 cells each cell has 1 member from the homologous pair in c (ploidy is reduced) chromosomes are in the replicated state and aligned by centromeres at the equatorial plane e. (3 pts) Products of meiosis of Moses cell 4 cells each cell has 1 sister from the replicated chromosomes in d thus, the chromosomes are unreplicated in the gametes gametes are haploid 1 member from each homologous pair, following from division of each M2 cell 3

4 NAME: KEY PID: Group#/Name: 12. (16 pts) Moses owner decides to breed him with Lena. Lena is homozygous dominant for both traits. a. (2 pts) What is Lena s genotype? HHEE Rewrite Moses genotype (from 16a): Hhee b. (2 pts) What is Lena s phenotype? Short hair (1pt), curled ears (1pt) c. (2 pts) What genotypes of gametes (eggs) is Lena capable of producing? HE only d. (2 pts) What genotypes of gametes (sperm) is Moses capable of producing? He, he e. (4 pts) Draw the Punnett Square for the cross between Moses and Lena. H E H e h e HHEe HhEe e. (2 pts) Predict the genotypic ratio for kittens resulting from this cross (note: you must include both the numerical value AND the resultant genotypes for full credit). 50% HHEe; 50% HhEe (also, 1:1, etc.) 1pt genotypes; 1pt - ratios f. (2 pts) Predict the phenotypic ratio for the kittens resulting from this cross (note: you must include both the numerical value AND the resultant phenotypes for full credit). 100% of kittens will be short-haired with curled ears 1pt genotypes; 1pt - ratios 4

5 NAME: KEY PID: Group#/Name: 13. (8 pts) A gene found in Brazil nuts, codes for 2S albumin, a protein rich in the essential amino acid methionine. In an effort to improve the nutritional quality of soybeans, researchers isolated the 2S albumin gene from Brazil nuts and inserted this gene into the soybean genome. 2S albumin can cause allergic reaction in many individuals with nut allergies. If an individual is allergic to the protein in Brazil nuts and is not allergic to soybeans, would you expect them to be allergic to the transgenic soybean? a. (3 pts) YES / NO. BRIEFLY explain. Yes. The 2S albumin gene will code for exactly the same protein whether in the Brazil nut or in the transgenic soybean. If an individual is allergic to the protein when it is found naturally in the Brazil nut, he/she will be allergic to the protein when the gene is expressed in the transgenic soybean. b. (5 pts) In the space below, draw a simple model to show how the above GMO would be made. Models will be diverse in their appearance. Models must represent the following information: 1pt Brazil nut contains 2S albumin gene 1pt the 2S albumin gene is isolated from the source (may include reference to restriction enzymes, etc.) 1pt plasmid (or other vector, such as virus or particle gun) is used to move the gene into the soybean 1pt the gene is integrated into the genome of the soybean 1pt the gene is copied to other cells in soybean by the process of mitotic cell division 19. (10 pts) In a box-and-arrow model, concepts are structures that are linked by behaviors. Behaviors are short phrases or linking words that clearly and concisely describe the relationship between structures. Behaviors are generally active, and therefore tend to be verbs, while structures are concepts or nouns. a. (8 pts) In the space below, construct a box and arrow model that demonstrates your understanding of the following concepts: gene, allele, DNA molecule, chromosome, protein, phenotype, mutation, and genetic variation. In your model, the concepts provided should be represented as structures you may use them more than once if it helps you build your model. Each concept listed above is represented accurately in association with a correct behavior. 2 pts awarded for correctly representing the associations indicated below, with correct/accurate descriptive words: - chromosome-dna DNA is represented as being equivalent to or a component of a chromosome; hierarchical organization is represented correctly - gene-allele alleles are indicated as alternative versions of genes; new alleles arise as the result of mutations in existing genes - allele-variation the consequence of mutations in existing alleles is that new alleles arise. Mutation is the origin of all variation and the ultimate source of genetic variation in a population - protein-phenotype alternative alleles code for the production of different proteins that are expressed as different phenotypes. Individuals in a population differ in their phenotypes owing to the activity of proteins encoded by different alleles. b. (2 pts) In a sentence or less, what is the function of your model? Variable must be consistent with information represented in model. Anticipated functions include: origin of genetic variation, etc. 5

6 NAME: KEY PID: Group#/Name: 14. (10 pts) In an on-line Evolution Pre-test, you were asked to use your current understanding of evolution by natural selection to explain the changes that occurred in the tree and animal (above). A complete explanation of natural selection would include 5 fundamental principles of evolution indicated in the left column of the table below. In the right column, explain how each concept is represented in (or relevant to) the scenario above. Genetic Variation Origin of Variation Inheritance Fitness Population Change Individuals (animals and plants) in the population differ from one another at any given time. Genetic differences account for the phenotypic variation we see for height of dinosaurs and plants. Random mutations in existing alleles result in different sequences of bases, thus new alleles. Random mutations resulted in alleles for taller heights in both dinosaurs and plants. Genetic information is passed from parent to offspring through the gametes. New alleles that conferred greater height were passed on to offspring of the dinosaurs and plants. Individuals differ in their ability to reproduce. Initially, plants that were taller were able to escape being eaten by dinosaurs, thus produced more offspring than short plants. Later, dinosaurs that were taller were able to reach the taller plants, acquire more resources, and reproduce more than short dinosaurs who couldn t reach the food. Alleles for height conferred the greatest fitness advantage for plants (early) and dinosaurs (later). Be definition, the fittest individuals reproduce the most they will pass their alleles on to their offspring. Over time, the alleles for height will become more abundant in the population (because tall individuals are reproducing the most), and the population will become taller on average. 6