Using the tryptophan operon as a model, explain a transcription pause site and the formation of a stem-loop
What will be an ideal response?
Answer: A pause in mRNA transcription occurs when tryptophan is in short supply and therefore requires the additional recruitment of a charged tryptophan tRNA for its synthesis. This lag or pause time provides the already synthesized mRNA component to bind to a different part of the transcript than would occur if there were no pause time. This different hairpin loop formed does not interact with the DNA sequence and therefore permits RNA polymerase to continue transcribing the entire mRNA, unlike what would occur if a lag time were absent.
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Chapter 11
24. The chromosomes are aligned at the spindle equator during a. anaphase. b. metaphase. c. interphase. d. prophase. e. telophase
True multicellularity is a major characteristic of
A. all eukaryotes and a few prokaryotes. B. protists, plants, and animals. C. prokaryotes and protists. D. animals and plants only. E. eukaryotes only.
Eukaryotes such as animal and plants cells differ from prokaryotes in that prokaryotes
lack a true nucleus. lack true DNA. use the cells membrane rather than ribosomes for making proteins. contain numerous organelles. undergo sexual reproduction.
Answer the following questions true (T) or false (F)
1. The chitin that makes up the exoskeleton of insects is a polymer of amino acids. 2. Glycogen is the carbohydrate found in plant cell walls. 3. Cholesterol is used to make other steroids in the body.