Huntington’s disease: Huntington’s disease is a disease in which certain parts of the brain waste away; symptoms usually begin later in life. In a community in Venezuela, an allele for Huntington’s disease (represented by the letter H) is completely dominantto the allele for no Huntington’s disease (represented by a lowercase h). The three possible parental genotypes are HH, Hh, and hh. There are six possible crossings that can be made between these genotypes (for example, HHxHH, HHxHh, etc.). Show the probabilitiesof the genotypesandphenotypesin the F1 generation from all sixpossible crossings.

HH x HH, HH x Hh, HH x hh, Hh x Hh, Hh x hh, hh x hh.

Explanation:

In a community in Venezuela, an allele for Huntington’s disease (represented by the letter H) is completely dominant to the allele for no Huntington’s disease (represented by a lowercase h).

The three possible parental genotypes are HH, Hh, and hh.

There are six possible crossings that can be made between these genotypes. These are HH x HH, HH x Hh, HH x hh, Hh x Hh, Hh x hh, hh x hh.

       HH x HH

Genotype: All HH

Phenotype: all express the huntington's disease (prob: 1)

      HH x Hh

Genotype: 1/2HH  1/2Hh

Phenotype: all express the huntington's disease (prob: 1)

     HH x hh

Genotype: All Hh

Phenotype: all express the huntington's disease (prob: 1)

    Hh x Hh

Genotype: 1/4HH, 1/2Hh, 1/4hh

Phenotype: 3/4 express the disease, and 1/4 do not express the disease

    Hh x hh

Genotype: 1/2Hh  1/2hh

Phenotype: 1/2 express the disease, and 1/2 do not express the disease.

   hh x hh.

Genotype: All hh

Phenotype: All do not express the huntington's disease (prob: 1)

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