Assume that a bacterial cell produces a lac repressor that is able to bind to the operator sequence of the
lac operon but cannot bind allolactose. Explain the effect of transcription of the lac operon when
lactose is not present, and then when it is present.
What will be an ideal response?
The lac repressor binds the operator in the absence of lactose to prevent transcription of the lac operon.
This would occur normally in this mutant bacterial cell. However, when lactose is present, allolactose
is supposed to bind the repressor so it is removed from the operator, allowing transcription. In this
mutant bacterial cell, the repressor cannot bind allolactose, and therefore, there will be no transcription
even in the presence of lactose.
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Which of the following statements about K-strategists is false?
A. They reproduce quickly. B. They produce few offspring. C. There is a lot of parental investment in the offspring. D. They evolve in stable environments. E. They evolve in environments with intense competition for limited food.
Sympatric speciation differs from allopatric speciation because with sympatric speciation
A. a population becomes geographically isolated. B. two populations of the same species merge to form a single population. C. polyploidy (changes in the number of sets of chromosomes) arises. D. hybrid zones form. E. temporal factors may arise without geographic isolation occurring and polyploidy may arise.
After the DNA is replicated, and it condenses in prophase, two identical rods of DNA are seen. These are
a. chromatids. b. centromeres. c. spindle fibers. d. kinetochores. e. chromatin.
Bronchioles differ from bronchi in that they
A) warm air to body temperature. B) contain only smooth muscle. C) filter and humidify air. D) can have alveoli attached to them. E) are lined by a ciliated epithelium.