A+ 70°F, a cell cultue is able to graw and divide farever, but aftera new mutation is found in the čeus, and the cells areat 99°F, mey Stop dividing after a few generahons.what* 16 ikery disiupted by the mutation for the cells to stopdividing after a few gener ution whenCompared to the 70°F when they diide and qrow indefinitely!growntheyaure95°Fgrown at

the mutation is a process in which there is a change in the sequence of the DNA. it can be a small…

A+ 70°F, a cell cultule is able to qraw and divide Parever, but aften a new mutatiùn is found in the čeus, and the cells are grown at 95. they Stop dividing after a few generahons. whät * io likery disrupted by the mulation for the cells to Stop dividing after a few gener ution when are groun at 95°F Compuared to the' 70°F Uwhen they divde and graw indefinil they mitery? itely

A+ 70°F, a cell cultule is able to qraw and divide Parever, but aften a new mutatiùn is found in the čeus, and the cells are grown at 95. they Stop dividing after a few generahons. whät * io likery disrupted by the mulation for the cells to Stop dividing after a few gener ution when are groun at 95°F Compuared to the' 70°F Uwhen they divde and graw indefinil they mitery? itely

Biology: The Unity and Diversity of Life (MindTap Course List)

15th Edition

ISBN:9781337408332

Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Publisher:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Chapter31: Animal Tissues And Organ Systems

Section: Chapter Questions

Problem 1CT: IPSCs are nearly identical to human embryonic stem cells in terms of gene expression, but there may...

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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?
The cells from a person’s malignant tumor were subjected to insitu hybridization using a probe that recognizes a unique sequenceon chromosome 14. The probe was detected only once in each ofthe cells. Explain this result, and speculate on its significance withregard to the malignant characteristics of these cells.
Look at the two yeast colonies in Figure Q4–3. Eachof these colonies contains about 100,000 cells descendedfrom a single yeast cell, originally somewhere in the mid-dle of the clump. A white colony arises when the Ade2 geneis expressed from its normal chromosomal location. Whenthe Ade2 gene is moved to a location near a telomere, itis packed into heterochromatin and inactivated in mostcells, giving rise to colonies that are mostly red. In theselargely red colonies, white sectors fan out from the middleof the colony. In both the red and white sectors, the Ade2 gene is still located near telomeres. Explain why white sec-tors have formed near the rim of the red colony. Based onthe patterns observed, what can you conclude about thepropagation of the transcriptional state of the Ade2 genefrom mother to daughter cells in this experiment?
Drosophila geneticists have isolated many mutationsthat modify position-effect variegation. Dominantsuppressors of variegation [Su(var)s] cause less frequent inactivation of genes brought near heterochromatin by chromosome rearrangements, whiledominant enhancers of variegation [E(var)s] causemore frequent inactivation of such genes.a. What effects would each of these two kinds of mutations have on position-effect variegation of thewhite gene in Drosophila (that is, would the eyesbe more red or more white)?b. Assuming that these Su(var) and E(var) mutationsare loss-of-function (null) alleles in the corresponding genes, what kinds of proteins do youthink these genes might encode?
A rare dominant mutation expressed at birth was studiedin humans. Records showed that six cases were discoveredin 40,000 live births. Family histories revealed that in twocases, the mutation was already present in one of the parents.Calculate the spontaneous mutation rate for this mutation.What are some underlying assumptions that may affect ourconclusions?
8. Using recombinant DNA techniques (which willbe described in Chapter 9), it is possible to take theDNA of a gene from any source and place it on achromosome in the nucleus of a yeast cell. Whenyou take the DNA for a human gene and put it into ayeast cell chromosome, the altered yeast cell canmake the human protein. But when you remove theDNA for a gene normally present on yeast mitochondrial chromosomes and put it on a yeast chromosome inthe nucleus, the yeast cell cannot synthesize the correctprotein, even though the gene comes from the sameorganism. Explain. What would you need to do to ensurethat such a yeast cell could make the correct protein?
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?
The origin of new β cells of the pancreas—fromstem cells or from preexisting β cells—was not resolveduntil a decade ago, when the technique of lineage tracingwas used to decide the issue. Using transgenic mice thatexpressed a tamoxifen-activated form of Cre recombinaseunder the control of the insulin promoter, which is activeonly in β cells, investigators could remove an inhibitorysegment of DNA and thereby allow expression of humanplacental alkaline phosphatase (HPAP), which can bedetected by histochemical staining. After a pulse of tamox-ifen that converted about 30% of β cells in young mice to cells that express HPAP, the investigators followed the per-centage of labeled β cells for a year, during which time thetotal number of β cells in the pancreas increased by 6.5-fold. How do you suppose the percentage of β cells wouldchange over time if new β cells were derived from stemcells? What if new β cells were derived from preexistingβ cells? Which hypothesis do the results in Figure…
........ cen not be true about in ditu hybridization. Use to reveal where gene expressed at mrna lvel. perform in none live animal/ tissues. reveal whether 2 genes are active in same cell. determine the function of gene
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?
An interesting phenomenon found in vertebrate DNAis the existence of pseudogenes, nonfunctional copiesof a gene found elsewhere in the genome. Some pseudogenes appear to have originated as double-strandedDNA copies of mature mRNA inserted into the chromosome; these copies later underwent mutations tomake them into pseudogenes.a. What sequence information might provide cluesthat the original source of some of these pseudogenes is cDNA copied in cells from mRNA andthen inserted into the genome?b. Would this mechanism of generating pseudogenesbe more likely to have operated if the pseudogenewas part of a gene family clustered in one region ofthe genome, or if it was instead part of a genefamily whose members are scattered around thegenome? Explain
Reverse translation is a term given to the process ofdeducing the DNA sequence that could encode a particular protein. If you had the amino acid sequenceTrp His Ile Met:a. What human nuclear DNA sequence could haveencoded these amino acids? (Include all possiblevariations.)b. What human mitochondrial DNA sequence couldhave encoded these amino acids? (Include allpossible variations.)