Concept explainers
a.
To determine:
The
Introduction:
The bread mold or the Saccharomyces cerevisiae is extensively studied in the field of genetics. The fusion of the gametes gives rise to the spores that are in a specific structure called ascus. The spores formed are eight in number and follow
b.
To determine:
The difference between the uniparental and biparental inheritance as seen in the bread mold and the validation of the paradoxical statement.
Introduction:
Microorganisms are small microscopic organisms that are present almost everywhere. They inhabit nearly all the areas from the air, water, soil, hot springs, snow, and so on. The microbes can be infectious or non-infectious. Microorganisms can be unicellular (single-celled) or multicellular.
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Genetics: From Genes to Genomes
- Baker's yeast, Saccharomyces cerevisiae, is a single-celled, diploid fungus (which is, of course, a eukaryote, that is capable of both meiosis and sexual reproduction). Wild type yeast can normally grow on solid or liquid minimal medium; you isolate three mutant strains which are no longer capable of growing on minimal medium alone, however, they can grow on medium supplemented with adenine. All three yeast strains are homozygous for the underlying alleles. When you cross mutant strain 1 and mutant strain 2, the offspring cannot grow on minimal medium alone and require adenine supplementation; when you cross mutant strain 1 and mutant strain 3, the offspring can grow on minimal medium alone and do not require adenine. A. What conclusions can you make about the alleles of mutant strains 1, 2, and 3 and their relationships with each other? B. What phenomenon is occurring in the cross between mutant strains 1 and 3? After crossing the F1 generation of the cross between mutant strains 1…arrow_forwardBaker's yeast, Saccharomyces cerevisiae, is a single-celled, diploid fungus (which is, of course, a eukaryote, that is capable of both meiosis and sexual reproduction). Wild type yeast can normally grow on solid or liquid minimal medium; you isolate three mutant strains which are no longer capable of growing on minimal medium alone, however, they can grow on medium supplemented with adenine. All three yeast strains are homozygous for the underlying alleles. When you cross mutant strain 1 and mutant strain 2, the offspring cannot grow on minimal medium alone and require adenine supplementation; when you cross mutant strain 1 and mutant strain 3, the offspring can grow on minimal medium alone and do not require adenine. A. What conclusions can you make about the alleles of mutant strains 1, 2, and 3 and their relationships with each other? B. What phenomenon is occurring in the cross between mutant strains 1 and 3?arrow_forwardA mutant haploid strain of Saccharomyces cerevisiae(yeast) called cox2-1 was found that was unable togrow on media containing glycerol as the sole sourceof carbon and energy. (Glycerol is a nonfermentablesubstrate for yeast.) This strain could, however, growon the fermentable substrate glucose. Researchers discovered that cox2-1 cells lack a mitochondrial proteincalled cytochrome c oxidase.a. Explain why cox2-1 cells can grow on mediumcontaining glucose but not on glycerol medium.arrow_forward
- Three haploid fungal mutants that require compound W for growth were isolated. Each mutant contains a recessive allele in a single gene. Three compounds (A, B and C) in the biosynthetic pathway to W are known, but their order in the pathway is unknown. Each compound is tested for its ability to support the growth of each of the three mutants. Phenotypes of all of the three mutants are shown in the following table (“+" indicates growth, "-" indicates no growth). A C W Mutant 1 Mutant 2 Mutant 3 What would be the phenotype of a haploid mutant that contains both mutant alleles in mutant 2 and 3? Phenotype refers to growth or absence of growth on compounds A, B, C and WN. O Like mutant 1 O Like mutant 2 Like mutant 3 O Like wild typearrow_forwardA mutant haploid strain of Saccharomyces cerevisiae(yeast) called cox2-1 was found that was unable togrow on media containing glycerol as the sole sourceof carbon and energy. (Glycerol is a nonfermentablesubstrate for yeast.) This strain could, however, growon the fermentable substrate glucose. Researchers discovered that cox2-1 cells lack a mitochondrial proteincalled cytochrome c oxidase.a. Explain why cox2-1 cells can grow on mediumcontaining glucose but not on glycerol medium.b. When cox2-1 was crossed with a wild-type yeaststrain and the resultant diploid cells were allowedto grow mitotically, it was found that about half thediploid clones were able to grow on glycerol, whilethe other half could not. The diploid clones thatcould grow on glycerol were induced to sporulate,and they yielded tetrads with four spores that wereall able to grow on glycerol medium. In all of thesetetrads, two of the haploid progeny were of matingtype a and two of mating type α. The diploids thatcould not…arrow_forwardYeast cells are eukaryotes, and they require a functional secretory pathway to grow and to maintain cellular organization. But surprisingly, when SRP is removed from yeast cells by deleting the relevant genes, the cells are still alive (although they grow slowly). a) How can yeast survive without SRP? Propose two alternative hypotheses. b) How might electron microscopy of normal and SRP-deficient yeast cells help you to distinguish between these two hypotheses?arrow_forward
- In your laboratory, you have an F − strain of E. coli that is resistant to streptomycin and is unable to metabolize lactose, but it can metabolize glucose. Therefore, this strain can grow on media that contain glucose and streptomycin, but it cannot grow on media containing only lactose. A researcher has sent you two E. coli strains in two separate tubes. One strain, let’s call it strain A, has an F factor that carries the genes that are required for lactose metabolism. On its chromosome, it also has the genes that are required for glucose metabolism. However, it is sensitive to streptomycin. This strain can grow on media containing lactose or glucose, but it cannot grow if streptomycin is added to the media. The second strain, let’s call it strain B, is an F − strain. On its chromosome, it has thegenes that are required for lactose and glucose metabolism. StrainB is also sensitive to streptomycin. Unfortunately, when strains A and B were sent to you, the labels had fallen off the…arrow_forward#22) You have identified five genes in S. cerevisiae that are induced when the yeast are grown in a high-salt (NaCl) medium. To study the potential roles of these genes in acclimation to the growth in high-salt conditions, you wish to examine the phenotypes of loss-and-gain-of-function alleles of each. How will you do this?arrow_forwardThe synthesis of flower pigments is known to be dependent on enzymatically controlled biosynthetic pathways. For the crosses shown here, postulate the role of mutant genes and their products in producing the observed phenotypes: (a) P1: white strain A * white strain B F1: all purple F2: 9/16 purple: 7/16 white (b) P1: white * pink F1: all purple F2: 9/16 purple: 3/16 pink: 4/16 whitearrow_forward
- Antibiotics such as chloramphenicol, tetracycline, and erythromycin inhibit protein synthesis in bacteria, but have no effect on the synthesis of proteins encoded by eukaryotic nuclear genes. Cycloheximide inhibits the synthesis of proteins encoded by nuclear genes, but has no effect on bacterial protein synthesis. How might these compounds be used to determine which proteins are encoded by mitochondrial and chloroplast genomes?arrow_forwardLeber’s Hereditary Optic Neuropathy (LHON) is a disease that involves degeneration of neural cells in the retina and results in loss of central vision. The disease is caused by mutations in any one of three genes in the mitochondrial genome that encode proteins involved in oxidative phosphorylation. In a genetic counseling clinic, a woman and her husband seek advice on the potential that any of their children would be afflicted with LHON. The husband's mother and father, both exhibit symptoms of the disease, but the woman does not. What is a reasonable advising statement to make? a. The couple should be advised that all of their children are likely to display symptoms of LHON. b. There is not enough information to advise this couple. c. The couple should be advised that none of their children will be affected. d. The couple should be advised that all their male children will display symptoms of LHON, but female children will be unaffected. e. The couple should be…arrow_forwardLeber's Hereditary Optic Neuropathy (LHON) is a disease that involves degeneration of neural cells in the retina and results in loss of central vision. The disease is caused by mutations in any one of three genes in the mitochondrial genome that encode proteins involved in oxidative phosphorylation. In a genetic counseling clinic, a woman and her husband seek advice on the potential that any of their children would be afflicted with LHON. The husband's mother and father, both exhibit symptoms of the disease, but the woman does not. What is a reasonable advising statement to make? There is not enough information to advise this couple. a. The couple should be advised that all of their children are likely to display symptoms of LHON. b. The couple should be advised that all their female children will display symptoms of LHON, but male children will be unaffected. C. The couple should be advised that all their male children will display symptoms of LHON, but female children will be…arrow_forward
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