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Concept explainers
a.
To determine:
The number of genes and operons depicted in the figure, the average gene density, and the representativeness of the value to the most bacterial genomes.
Introduction:
The mentioned figure shows the RNA-Seq results from the RNA-Seq experiment. In the analysis part, the computer lines up each of cDNA sequence read with the genome sequence of the bacterium.
b.
To determine:
Whether the given data proves that t2110 is nonfunctional and the process by which scientists were able to assign a direction to the transcription when no transcript of the gene was found.
Introduction:
In the performed experiment, it was found that no transcripts for the gene t2110 were detected.
c.
To determine:
The evidence that suggests the existence of an attenuation or riboswitch mechanism, causing premature transcriptional termination of an operon and the observation of any of the operon that might be controlled by such a mechanism.
Introduction:
The process of attenuation is considered as the method of control in some bacterial operons, and it causes premature termination of transcription.
d.
To determine:
The depiction of the given figure if the antisense mechanism was involved in controlling the gene or operon.
Introduction:
The mentioned figure does not provide any evidence that any of the genes or operons are regulated by an antisense transcript.
e.
To determine:
The possibility of the transcription of the galM gene from the different promoter.
Introduction:
The given figure depicts galM gene to be a part of the operon containing galETK. There is even a possibility that galM is transcribed from a separate promoter.
f.
To determine:
Whether the data shown in the figure reveal the presence of a regulatory mechanism in relation to an sRNA occluding the ribosome binding site.
Introduction:
The ribosome binding site is present in upstream to the start codon. It is a sequence of nucleotides which play an important role in recruiting the ribosome at the initiation of the translation process.
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Chapter 15 Solutions
Genetics: From Genes to Genomes, 5th edition
- The streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the lowest beta-galactosidase enzyme activity, when grown in the lactose medium. Orpt o* z* r* Orpt ot z* Y OrptoztY Orrotzr OrPotz*Yarrow_forwardAnswer the following questions: 1. Given the following genotypes, explain how the mutation (identified by a () superscript will affect E. coli grown in lactose medium. Will the lac operon be on or off? Will there be a complete set of gene products from the loc operon? What will be the implication of the missing gene product, if ever? Will the cell be able to survive in the lactose medium or not? a. p' oE Y b. p'o Y d. po varrow_forward
- The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/). The possible answers indicate with a ʺ+ʺ or a ʺ-ʺ whether β-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)Genotype F: I+ Oc Z-/ Fʹ I- O+ Z+ KEY:I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)arrow_forwardA strain of E. coli has the genotypes shown below at the lac operon, where I = regulator gene, P = promoter, O = operator, Z = βgalactosidase gene, and Y = permease gene. The superscript+ indicates a wild-type allele,c indicates a constitutive mutation, and− indicates a defective mutation. For each genotype, indicate whether the enzyme will be synthesized or not synthesized when lactose is present or absent by placing a + for synthesis occurring and a − for synthesis not occurring in the appropriate blank. Explain your reasoning for each answer.arrow_forwardExamine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genAarrow_forward
- A number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the lowest beta-galactosidase enzyme activity, when grown in the lactose medium. OF POZY Ort Ptot Z¹ Yt Ort p²o+z¹Y+ Orpt ot ztyarrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. You are given a new strain of Escherichia coli with the following lac operon genotype: p+0°Z•Y*A +// P*O*Z*Y+ A- (i) Explain how the lac I gene affects gene expression. (ii) Explain the function of the lacP in the bacterial operon. (iii) Which part of the lac operon is cis-dominant? Explain.arrow_forwardHow long would it take for the E. coli RNA polymerase to synthesize the primary transcript for the E. coli genes encoding the enzymes for lactose metabolism, the 5,300 bp5,300 bp lac operon? Assume an average elongation rate of 7070 nucleotides per second. a)How far along the DNA would the transcription "bubble" formed by RNA polymerase move in 10 seconds10 seconds? b)Assuming that human Pol II transcribes at a similar rate, how long does it take to transcribe the 2,000,000 bp2,000,000 bp dystrophin gene?arrow_forward
- For the given genotypes (associated with the lac operon in E. coli), indicate with a "+" or "-" whether functional B - galactosidase would be expected to be produced in the indicated conditions, assuming low glucose levels. B - galactosidase production Genotype No lactose With lactose a) I- O+ Z+ / F' I+ O+ Z+ b) IS O+ Z+/ F' I+ O+ Z+arrow_forwardIf a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??arrow_forwardAnother class of suppressor mutations, not describedin the chapter, are mutations that suppress missensemutations.a. Why would bacterial strains carrying such missense suppressor mutations generally grow moreslowly than strains carrying nonsense suppressormutations?arrow_forward
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