Question at position 18 Cells of which bacterial genotype would be able to utilize lactose as an energy source?I+O+Z+Y- / (I+O+Z-Y+)I+O+Z-Y+ISO+Z+Y+I+OCZ+Y- / (I+O+Z-Y-)Clear my selection单项选择题
A
I+O+Z+Y- / (I+O+Z-Y+)
B
I+O+Z-Y+
C
ISO+Z+Y+
D
I+OCZ+Y- / (I+O+Z-Y-)

Question

Question at position 18 Cells of which bacterial genotype would be able to utilize lactose as an energy source?I+O+Z+Y- / (I+O+Z-Y+)I+O+Z-Y+ISO+Z+Y+I+OCZ+Y- / (I+O+Z-Y-)Clear my selection

BlackTom AI · Accepted Answer

Question: Cells of which bacterial genotype would be able to utilize lactose as an energy source? I+O+Z+Y- / (I+O+Z-Y+) I+O+Z-Y+ ISO+Z+Y+ I+OCZ+Y- / (I+O+Z-Y-)

Option 1: I+O+Z+Y- / (I+O+Z-Y+). In this genotype, Z+ is present but Y is mutated to Y-, meaning beta-galactosidase activity could be intact while lactose import via LacY would be compromised or absent depending on which copy is functional. Since lactose utilization requires both lactose permease (Y+) to transport lactose into the cell and beta-galactosidase (Z+) to metabolize it, the presence of Y- would hinder lactose utilization. This option is therefore unlikely to support lactose metabolism.

Option 2: I+O+Z-Y+. Here Z is inactivated (Z-), so even if lactose is transported, the enzyme needed to cleave lactose into usable sugars is absent. Without functional beta-galactosidase, lactose cannot be metabolized efficiently, so this genotype cannot utilize lactose as an energy source. This option is incorrect.

Option 3: ISO+Z+Y+. In this genotype, all of I, O, Z, and Y are functional (I+, O+, Z+, Y+). With both LacZ (Z+) and LacY (Y+) functional, lactose can be imported into the cell and metabolized, enabling utilization of lactose as an energy source. This aligns with the requirement for both transport and enzymatic processing.

Option 4: I+OCZ+Y- / (I+O+Z-Y-). This option shows a mixture of elements with Y- (lactose permease nonfunctional) and Z+ (beta-galactosidase functional) but lacking a functional permease. Without LacY, lactose import is limited, so lactose utilization would be ineffective. This makes it an unlikely genotype for lactose utilization.

In summary, the critical factors for lactose utilization are a functional lactose permease (Y+) to import lactose and functional beta-galactosidase (Z+) to metabolize it. Only Option 3 provides both Y+ and Z+ in addition to functional I and O elements, making it capable of utilizing lactose.

Question at position 18 Cells of which bacterial genotype would be able to utilize lactose as an energy source?I+O+Z+Y- / (I+O+Z-Y+)I+O+Z-Y+ISO+Z+Y+I+OCZ+Y- / (I+O+Z-Y-)Clear my selection单项选择题

类似问题

True or False: Transcription of the trans-acting regulatory gene lacI depends on the presence of lactose.

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