Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype .

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Answer 1

Textbook Question

Chapter 20, Problem 20.1CC

Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype.

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

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Students have asked these similar questions

If glucose is not available, but lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?

What would happen if the operator sequence of the lac operon contained a mutation that prevented the repressor protein from binding the operator? (Explain what would happen both in the presence and absence of lactose)

If glucose levels in the cell are high and lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?

Answer 2

Textbook Question

Chapter 20, Problem 20.1CC

Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype.

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

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Answer 3

Textbook Question

Chapter 20, Problem 20.1CC

Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype.

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

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Answer 4

Textbook Question

Chapter 20, Problem 20.1CC

Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype.

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

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Answer 5

Textbook Question

Answer 6

Textbook Question

Answer 7

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

Answer 8

Expert Solution & Answer

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

Answer 9

Expert Solution & Answer

Answer 10

Expert Solution & Answer

Answer 11

Summary Introduction

To determine: Two possible genotypes for a strain of haploid Escherichia coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium.

Introduction: E. coli has a lactose operon, also called the lac operon. It is an inducible operon. This operon helps in the digestion and transportation of lactose. By genetic analysis of the lac operon of E. coli of various mutants, a lot of information has been retrieved.

Answer 12

Explanation of Solution

The lac operon under normal conditions can be represented by the genotype I⁺P⁺O⁺Z⁺ where the Z product will be expressed in the presence of lactose. The I gene represents the repressor gene, P represents the lac promoter gene, O represents the lac operator gene and the Z gene represents the protein product that is formed.

Two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are as follows:

If the I gene has a mutation such that it shows the suppressor genotype, a repressor will be formed in every case. This repressor will bind to the operator in every case, that is whether a lactose inducer is present or absent. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I^sP⁺O⁺Z⁺.
If the P gene has a mutation, the promoter will be non-functional. When the promoter is non-functional, the RNA polymerase enzyme will not be able to identify the promoter. Thus, the transcription of the lac genes are suppressed and will never be transcribed. The genotype of such a strain of bacteria can be represented as I⁺P^-O⁺Z⁺.

Thus, two possible genotypes for a strain of haploid E. coli bacteria in which the genes of the lac operon are never transcribed and the bacteria cannot grow in the lactose-containing medium are I^sP⁺O⁺Z⁺ and I⁺P^-O⁺Z⁺.

Answer 13

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Suppose you are analyzing a haploid E. coli strain and discover that the genes of the lac operon are never transcribed and that the bacteria cannot grow in lactose-containing medium. Provide two possible genotypes for your bacteria that would explain this phenotype .

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