A fly embryo that expresses the bicoid mutant phenotype

Question

A.  is genetically wild-type, but has a bicoid mutant mother.
B.  is mutant for bicoid and has a bicoid mutant mother.
C.  may be either genetically wild-type or mutant for bicoid, but definitely has a bicoid mutant mother.
D.  can be either genetically wild-type or mutant for bicoid. The genotype of the mother cannot be determined from the information provided.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

  Gather Content
· What do you already know about maternal genes?

  Consider Possibilities · Consider the different answer options. Which can you rule out?

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  may be either genetically wild-type or mutant for bicoid, but definitely has a bicoid mutant mother.


Clarify Question
· What is the key concept addressed by the question?
        o This question addresses maternal genes.
· What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
· What key words does the question contain and what do they mean?
        o The bicoid gene is a maternal gene that specifies the anterior end of the fly embryo.

  Gather Content
· What do you already know about maternal genes?
        o Maternal genes like bicoid are unusual because they are expressed in the nurse cells of the ovary, not in the embryo itself.
        o The nurse cells deposit bicoid mRNA into the anterior end of the fly egg where it becomes anchored.
        o Bicoid protein is necessary to determine anterior development of the embryo.
        o So if the mother is mutant, the progeny exhibit the phenotype, whether or not they are homozygous for the mutation.

  Consider Possibilities · Consider the different answer options. Which can you rule out?
        o Can we conclude that the embryo with the phenotype is genetically wild-type, but has a bicoid mutant mother? No, we cannot determine the genotype of the embryo at all.
        o Can we conclude that the embryo with the phenotype is mutant for bicoid and has a bicoid mutant mother? No, we cannot determine the genotype of the embryo at all.
        o Can we conclude that the embryo with the phenotype can be either genetically wild-type or mutant for bicoid. The genotype of the mother cannot be determined from the information provided? No, in fact the genotype of the mother must be homozygous mutant for bicoid.

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o If the individual fly embryo has the bicoid mutant phenotype, we can conclude that it may be either genetically wild-type or mutant for bicoid, but definitely has a bicoid mutant mother.

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked what you can conclude about a fly embryo that has the bicoid mutant phenotype.
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that as a maternal gene, the phenotype of an embryo reflects the genotype of the mother, not the embryo itself.