Instructions:
•
Answer the questions based on your knowledge of the first law of Mendel.
•
Keep the presentation of your homework ordered and clean.
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Do it yourselve, do your best and ask questions during the next class. It is
your knowledge and understanding what matters.
DBQ: coat color in the house mouse
In the early years of the 20th century, many crossing experiments were done in a
similar way to those of Mendel. The French genetist Lucien Cuénot used the
house mouse, Mus musculus, to see whether the principles that Mendel had
discovered also operated in animals. He crossed normal grey-colored mice with
albino mice. The hybrid mice that were produced where all grey. These grey
hybrids were crossed together and produced 198 grey and 72 albino offspring.
1. Calculate the ratio between grey and albino offspring, showing your working
(2)
2. Deduce the color of coat that is due to a recessive allele, with two reasons for
your answer (2)
3. Choose suitable symbols for the alleles for grey and albino coat and list the
posible genotypes of mice using your symbols, together with the phenotype and
each genotype (3)
4. Using hte headings shown to the right, explain how the observed ratio of grey
and albino mice was produced (5)
5. Suggest how one gene can determine wheter the mice had grey fur and black
eyes or White fur and red eyes (2)
Key to alleles:
Parental phenotypes
Parental genotypes
Alleles in gametes
Hybrid phenotype
Hybrid genotype
Alleles in gametes
Genotypes and
phenotypes of offspring
of hybrid mice, shown
using a punnett grid.