Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 16, Problem 5PDQ
For the lac genotypes shown in the following table, predict whether the structural genes (Z) are constitutive, permanently repressed, or inducible in the presence of lactose.
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For the genotypes and conditions (lactose present or absent) shown in the following Table 2,
predict whether the expression of beta-galactosidase is inducible (I), noninducible (N) or
constitutive (C). Explain your reason.
Table 2
Genotype
I*p*O°z*
Condition
(i)
No lactose
(ii)
I*P*O*Z+
Lactose
I*P-0*Z*
(iii)
(iv)
Lactose
ISP+O°Z+
Lactose
(v)
Ip*o°Z+
No lactose
The lac genotypes are as shown below:
P+OcZ-Y+A+// P¯O+Z+Y+A+
(i)
The lac operon consists of three structural genes, lacZ, lacY and lacA. Which
structural genes are involved in lactose metabolism? Explain.
(ii)
Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote.
(iii)
What is the function of the promoter in the bacterial operon?
For the lac genotypes of Escherichia coli shown in the following Table 1, predict the expression
of beta-galactosidase (Z) and permease (Y) is inducible or noninducible or constitutive. Explain
your answer.
Table 1
Genotype
I-P+O+Z+Y+
(i)
(ii) I+P+OCZ+Y+
(iii) ISP+O+Z+Y+
(iv) I+P+O+Z+Y-//I+P-O+Z+Y+
(v) ISP+OcZ+Y+//I-P+O+Z+Y-
Condition
No lactose
No lactose
lactose
lactose
No lactose
Chapter 16 Solutions
Concepts of Genetics (12th Edition)
Ch. 16 - Even though the lac Z, Y, and A structural genes...Ch. 16 - Predict the level of genetic activity of the lac...Ch. 16 - Prob. 1CSCh. 16 - Prob. 2CSCh. 16 - Prob. 3CSCh. 16 - HOW DO WE KNOW? In this chapter, we focused on the...Ch. 16 - Prob. 2PDQCh. 16 - Contrast positive versus negative control of gene...Ch. 16 - Contrast the role of the repressor in an inducible...Ch. 16 - For the lac genotypes shown in the following...
Ch. 16 - For the genotypes and conditions (lactose present...Ch. 16 - The locations of numerous lacI and lacIS mutations...Ch. 16 - Prob. 8PDQCh. 16 - Prob. 9PDQCh. 16 - Predict the effect on the inducibility of the lac...Ch. 16 - Erythritol, a natural sugar abundant in fruits and...Ch. 16 - Prob. 12PDQCh. 16 - Prob. 13PDQCh. 16 - Neelaredoxin is a 15-kDa protein that is a gene...Ch. 16 - The creation of milk products such as cheeses and...Ch. 16 - Both attenuation of the trp operon in E. coli and...Ch. 16 - Prob. 17PDQCh. 16 - Prob. 18ESPCh. 16 - In a theoretical operon, genes A, B, C, and D...Ch. 16 - A bacterial operon is responsible for the...Ch. 16 - A marine bacterium is isolated and shown to...Ch. 16 - Prob. 22ESPCh. 16 - Prob. 23ESP
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- Define the Comparison of Gene Activity ( +or -) in the Presence or Absence of Lactose for Various E. coli Genotypes ?arrow_forwardFor the genotypes and conditions (lactose present or absent) shown in the following Table 2, predict whether the expression of beta-galactosidase is inducible (I), noninducible (N) or constitutive (C). Explain your reason. Table 2 Genotype I*p*o°z+ Condition (i) No lactose (ii) (iii) (iv) I*P*O*Z+ I*P•O*Z* I$P*O°Z* Lactose Lactose Lactose (v) IP*0°Z+ No lactosearrow_forwardFor each of the E. coli strains that follow, indicate theeffect of the genotype on the expression of the trpEand trpC genes in the presence or absence of tryptophan. [In the wild type (R+ P+ o+ att+ trpE+ trpC+),trpC and trpE are fully repressed in the presence oftryptophan and are fully expressed in the absence oftryptophan.]R = repressor gene; Rnproduct cannot bind tryptophan; R− product cannot bind operatoro = operator for the trp operon; o− cannot bind repressoratt = attenuator; att− is a deletion of the attenuatorP = promoter; P− is a deletion of the trp operonpromotertrpE− and trpC− are null (loss-of-function) mutationsa. R+ P− o+ att+ trpE+ trpC+b. R− P+ o+ att+ trpE+ trpC+c. RnP+ o+ att+ trpE+ trpC+d. R− P+ o+ att− trpE+ trpC+e. R+ P+ o− att+ trpE+ trpC−/R− P+ o+ att+trpE− trpC+f. R+ P− o+ att+ trpE+ trpC−/R− P+ o+ att+trpE− trpC+g. R+ P+ o− att− trpE+ trpC−/R− P+ o− att+trpE− trpC+arrow_forward
- In studies of the amino acid sequence of wild-type and mutant forms of tryptophan synthetase in E. coli, the following changes have been observed: Determine a set of triplet codes in which only a single-nucleotide change produces each amino acid change.arrow_forwardDescribe how polymorphisms is found at 13910-C/T and 22018-G/A in the regulatory area of the lactase gene (LCT). And elaborate the mechanism for two polymorphisms causing mutation from 13910-C/T and 22018-G/A to 13910-C/C or 22018-G/G variants in lactase intolerance disorder. also, how LCT gene is corelated to lactase intolerance disorder?arrow_forwardA particular type of anemia in humans, called b-thalassemia,results from a severe reduction or absence of the normal b-globinchain of hemoglobin. However, the g@globin chain, normally onlyexpressed during fetal development, can functionally substitutefor b-globin. A variety of studies have explored the use of thenucleoside 5-azacytidine for the expression of g-globin in adultpatients with b-thalassemia.(a) How might 5-azacytidine lead to expression of g-globin inadult patients?(b) Explain why this drug may also have some adverse side effects.arrow_forward
- Why is it adaptive for the structural genes for using lactose to be under the control of a single promoter (i.e., synthesize a polycistronic message rather than three monocistronic messages)? a. For efficient absorption and catabolism of lactose, structural genes send a single signal. This is why polycistronic message is favored more than the monocistronic message since the former involves transmission of numerous messages in initiation and termination. b. Polycistronic message is favored more than the monocistronic message. c. Polycistronic message is favored more than the monocistronic message since the former involves transmission of numerous messages in initiation and termination. d. For an efficient absorption and catabolism of lactose, structural genes send a single signal only. e. Polycistronic message is favored more than the monocistronic message since the former involves transmission of single message in initiation and termination.arrow_forwardCTP synthetase catalyzes the glutamine-dependent conversion of UTP to CTP. The enzyme is allosterically inhibited by the product, CTP. Mamma- lian cells defective in this allosteric inhibition are found to have a complex phenotype: They require thymidine in the growth medium, they have unbal- anced nucleotide pools, and they have an elevated spontaneous mutation rate. Explain the likely basis for these observations.arrow_forwardConsider a mutant form of the lac repressor protein whose ΔGo for binding DNA differs from that of the wild-type protein by 2 kcal/mol, the approximate free energy equivalent of a single hydrogen bond. What is the difference (i.e., the ratio) of the Kd values (for DNA binding) of the wild-type versus the mutant lac repressor protein?arrow_forward
- Considerable effort has been directed toward determining the genes in which sequence variation contributes to the development of type 2 diabetes. Approximately 800 genes have been implicated. Propose an explanation for this observation.arrow_forwardConsider the mechanism of the enzyme RNase: What would happen to the Km (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a lysine? Explain. What would happen to the Kcat (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a valine? Explain.arrow_forwardGive the levels of Beta-galactosidase activity (high or low or zero) expected for the following partial diploids for the lac operon strains.arrow_forward
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