BIO260H1 Study Guide - Midterm Guide: Growth Medium, Operon, Reca
BIO260 midterm exam McCourt section
Name ___________________________
Student # ________________________
1
Answer all questions in the boxes provided. Writing outside these areas will not be
marked. Total marks = 25.
1. An operon responsible for the utilization of a sugar Q is regulated by a gene called
KYU. When Q is added to the growth medium the enzyme, Qase, is made; otherwise
Qase is not made. If the gene KYU is deleted (denoted Δkyu), no Qase is made. The
partial diploid KYU+/Δkyu is inducible. Two types of point mutants of KYU are found:
kyu1, which never makes Qase, and kyu2, which makes the enzyme constitutively. The
partial diploids KYU+/kyu1 and KYU+/kyu2 are inducible and constitutive, respectively.
(Total 5 marks)
a. Is the KYU gene a positive or negative regulator? How do you know this? (0.5 marks)
b. Is the kyu1 mutant dominant or recessive? How do you know this? (0.5 marks)
c. Is the kyu2 mutant dominant or recessive? How do you know this? (0.5 marks)
d. Draw a simple model of the Qase regulatory system. Your model must explain the
phenotypes of the kyu1 and kyu2 mutants. (3.5 marks)
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Document Summary
Writing outside these areas will not be marked. Total marks = 25: an operon responsible for the utilization of a sugar q is regulated by a gene called. When q is added to the growth medium the enzyme, qase, is made; otherwise. If the gene kyu is deleted (denoted kyu), no qase is made. Two types of point mutants of kyu are found: kyu1, which never makes qase, and kyu2, which makes the enzyme constitutively. How do you know this? (0. 5 marks: draw a simple model of the qase regulatory system. Your model must explain the phenotypes of the kyu1 and kyu2 mutants. (3. 5 marks) Student # _______________________: the gale gene in e. coli encodes the last step in galactose utilization. In the presence of galactose recessive mutations in the gale gene are lethal to e. coli. You plate a gale mutant strain out on lactose and only a few colonies form the next day.
