Principles of Biology : Homework
#6, Genetics 1
This homework assignment consists of problems in genetics. It is worth
10 points. Each problem is worth 5 points (with the A sections=2 and
the B sections=3).
You do not need to restate the question for these problems, but I would
like your answers to be complete enough that the problem it addresses
is obvious. You may find drawing the tables by hand is easier than
trying to build them on the computer, and neat tables will be fine.
Assume: Drosophila Mendelian genetics
where: wild type is dominant to the mutant
wingless (Use A and a) and where the mutation Eyeless is dominant to
having eyes (use E and e). In each case, the dominant allele is
indicated by the upper case letter and the recessive allele is
indicated by the lower case letter. (NOTE: The Eyeless gene, E, is a
dominant gene and is always expressed).
Problem 1.
A wild type fly,
coming from a colony of all wild type flies,
mates with a fly that has no eyes and that came from a colony of
eyeless flies. This is the "P" generation in this exercise. Assuming
that both these parents are homozygous for their own "eye" gene (which
ever it is), answer the
following questions:
A.
Construct the Punnett square for this cross. See sample tables. Show
the phenotypes and the genotypes
of the parents above the table.
Indicate the donation of gametes from each parent to the left and top
edges of the table as appropriate. Fill out the square, combing gametes
from each parent to create a genotype for each square in the table.
Underneath the genotype, indicate the phenotype. What are the ratios of
the phenotypes? What are the corresponding genotype ratios?
B. Imagine
that two flies resulting from the cross
indicated above, mate and have hundreds of offspring (this is called
the F1 cross).
Indicate the genotype and phenotype of this generation, and
then, below this, construct a Punnett square that will predict the
number and types of phenotypes and
genotypes of the F2 generation. Label and layout as in the
sample above.
Problem 2.
A wild type fly, coming from a
colony of all wild type flies (as in Problem 1), mates with a fly that
has no wings and has no eyes and has come from a colony of eyeless,
wingless flies. As above, use the given symbols for these genes in your
answers.
A.
Construct the Punnett square for this cross. Show
the phenotypes and the genotypes
of the parents above the table.
Indicate the donation of gametes from each parent to the left and top
edges of the table as appropriate. Fill out the square, combing gametes
from each parent to create a genotype for each square in the table.
Underneath the genotype, indicate the phenotype. What are the ratios of
the phenotypes? What are the corresponding genotype ratios?
B. Imagine
that two flies resulting from the cross
indicated above, mate and have hundreds of offspring (this is called
the F1 cross).
Indicate the genotype and phenotype of this generation, and
then, below this, construct a Punnett square that will predict the
number and types of phenotypes
of the F2 generation. Label and layout as in sample
above.