4. Normal yeast cells can survive on a diet of sugars, a few simple salts and one vitamin. They can make all of their amino acids and other vitamins using what can be found in their diet. You identify a mutant strain that can only survive if given alanine, which is one of the amino acids. The mutation is recessive. Based on this information, what would you predict that the normal function of the dominant allele is?

4. Normal yeast cells can survive on a diet of sugars, a few simple salts and one vitamin. They can make all of their amino acids and other vitamins using what can be found in their diet. You identify a mutant strain that can only survive if given alanine, which is one of the amino acids. The mutation is recessive. Based on this information, what would you predict that the normal function of the dominant allele is?

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter11: Genome Alterations: Mutation And Epigenetics

Section: Chapter Questions

Problem 16QP: Familial retinoblastoma, a rare autosomal dominant defect, arose in a large family that had no prior...

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When 1 million cells of a culture of haploid yeastcarrying a met− auxotrophic mutation were plated onpetri plates lacking methionine (Met), five coloniesgrew. You would expect cells in which the originalmet− mutation was reversed (by a base change back tothe original sequence) would grow on the media lackingmethionine, but some of these apparent reversions couldbe due to a mutation in a different gene that somehowsuppresses the original met− mutations. How wouldyou be able to determine if the mutations in your fivecolonies were due either to a precise reversion of theoriginal met− mutation or to the generation of a suppressor mutation in a gene on another chromosome?
Explain what happened to the b allele that allowed gene conversion to occur.
. You receive four strains of yeast in the mail, and theaccompanying instructions state that each strain contains a single copy of transgene A. You grow the fourstrains and determine that only three strains expressthe protein product of transgene A. Further analysisreveals that transgene A is located at a different position in the yeast genome in each of the four strains.Provide a hypothesis to explain this result
In most cases, the rate of synonymous substitution for a gene is higherthan the rate of nonsynonymous substitution. Sometimes, however, therate of nonsynonymous substitution is higher. When would you expectto see this? What might bring it about?
Null mutations are valuable genetic resources becausethey allow a researcher to determine what happens to anorganism in the complete absence of a particular protein. However, it is often not a trivial matter to determinewhether a mutation represents the null state of the gene.a. Geneticists sometimes use the following test forthe nullness of an allele in a diploid organism: If theabnormal phenotype seen in a homozygote for theallele is identical to that seen in a heterozygote(where one chromosome carries the allele in question and the homologous chromosome is known tobe completely deleted for the gene) then the alleleis null. What is the underlying rationale for thistest? What limitations might there be in interpreting such a result?b. Can you think of other methods to determinewhether an allele represents the null state of a particular gene?
Deletions in bacterial chromosomes give the following data: Region of deletion Al Gene A activity +++ A2 АЗ A4 AS +++ (i) Where is the gene located? Explain your answer. Name the scientific term that describes the appearance of a recessive phenotype due to deletion of dominant gene. (ii) (iii) The phenotypic consequences of deletion depend on two factors. What are they? Give one example of human genetic disorder caused by chromosomal deletion by indicating the region of deletion in chromosome. (iv)
during bacterial transformation, DNA that enters acell is not an intact chromosome; instead it consists ofrandomly generated fragments of chromosomal DNA.In a transformation where the donor DNA was from abacterial strain that was a+ b+ c+ and the recipient wasa b c, 55% of the cells that became a+ were also transformed to c+. But only 2% of the a+ cells were b+. Isgene b or c closer to gene a?
An interesting trait that some bacteria exhibit is resistance to beingkilled by antibiotics. For example, certain strains of bacteria areresistant to tetracycline, whereas other strains are sensitive to tetracycline.Describe an experiment you would carry out to demonstratethat tetracycline resistance is an inherited trait encoded bythe DNA of the resistant strain.
A cystic-fibrosis mutation in a certain pedigree is due toa single nucleotide-pair change. This change destroys anEcoRI restriction site normally found in this position.How would you use this information in counseling members of this family about their likelihood of being carriers? State the precise experiments needed. Assume thatyou find that a woman in this family is a carrier, and ittranspires that she is married to an unrelated man whoalso is a heterozygote for cystic fibrosis, but, in his case, itis a different mutation in the same gene. How would youcounsel this couple about the risks of a child’s having cystic fibrosis?
Researchers have identified a gene in humans that (when mutant)causes severe dwarfism and mental impairment. This disorder isinherited in an autosomal recessive manner, and the mutant alleleis known to be a loss-of-function mutation. The same gene hasbeen found in mice, although a mutant version of the gene has notbeen discovered in mice. To develop drugs and an effective therapyto treat this disorder in humans, it would be experimentallyuseful to have a mouse model. In other words, it would be desirableto develop a strain of mice that carry the mutant allele in thehomozygous condition. Experimentally, how would you developsuch a strain?
Over a period of several years, a large hospital kepttrack of the number of births of babies displaying thetrait achondroplasia. Achondroplasia is a very rareautosomal dominant condition resulting in dwarfismwith abnormal body proportions. After 120,000births, it was noted that 27 babies had been born withachondroplasia. One physician was interested in determining how many of these dwarf babies resultedfrom new mutations and whether the apparent mutation rate in this geographical area was higher thannormal. He looked up the families of the 27 dwarfbirths and discovered that four of the dwarf babieshad a dwarf parent. What is the apparent mutationrate of the achondroplasia gene in this population? Isit unusually high or low?
A yeast strain with a mutant spo11- allele has been isolated. The mutant allele is nonfunctional; it makes no spo11 protein. What do you suppose is the phenotype of this mutant strain?