A zebrafish biologist isolates 3 viable mutants, named h1, s2, and z3. When homo
ID: 35080 • Letter: A
Question
A zebrafish biologist isolates 3 viable mutants, named h1, s2, and z3. When homozygous, the mutants grin all the time, which we call the grinner phenotype after a known gene Grinner (Gr) that has that phenotype. The only known Gr allele is t51. Since the mutants are not lethal they are carried as pure lines.
He makes the following crosses:
(complement or not?)
Crosses WT mut (C/NC ?) Complete the table
1. h1 x Grt51 100 0 _______
2. s2 x Grt51 100 0 _______
3. z3 x Grt51 0 100 _______
4. h1 x s2 0 100 _______
5. h1 x z3 100 0 _______
6. s2 x z3 100 0 _______
a) It looks like there is one new gene. Which crosses tell you that?
b) The name of the new gene is called Smirk (Sm). What are all the alleles for the Gr and Sm genes?
Gr here:_________________ Sm here: ________________
c) Use your nomenclature to describe the complete
genotypes of the #6 s2 x z3 cross above.__________________x___________________
d) Now, you take your WT fish that you got from the s2xz3 cross, and you mate them.
What ratio of WT and mutants would you expect: (WT : mut : new pheno)
if the double mutant looked like grinner? ____ : ____
if the double mutant had a new phenotype? ____ : ____ : ___
Explanation / Answer
z3 x Grt51 0 100 tells that there is 1 gene
z3 x Grt51 0 100 _______
4. h1 x s2 0 100
these two complement, rest not
Gr allele is t51 and Sm allele is s2
s2 x z3: H1s2Z3 8H1S2z3
s2 x z3: double mutant is not griner, no new phenotype
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