Summary of Huntington’s Disease

1. Summary of Huntington’s Disease Overview and Symptoms: • Occurs from the genetically programmed degeneration of nerve cells • Causes uncontrolled movement, lose of intellectual faculties, and emotional disturbance Interesting Facts: • No family history found in 1-3% of people with Huntington’s Disease • HG will definitely affect your life if one is inherited with the HG gene.

2. Punnet Squares • Ratio of the chance of offspring inheriting Huntington’s Disease; ratio determined by parents • Each punnet square represents the chances PER CHILD heterozygous recessive homozygous dominant Mother homozygous dominant Father H h H h h H h h

3. Probability Using Ratios and Percentages • Ratios: • Must equal 4; 4 possibilities • Ratio is lined up in this format: Homozygous dominant : heterozygous dominant : homozygous recessive ex: 1 : 2 : 1 ex: 1HH : 2Hh : 1hh • Percentages: • Must equal 100; each possibility equals 25% • Put percentages into the ratio ex: 25% : 50% : 25% ex: 25%HH : 50%Hh : 25%hh H h H h Percentages Pie Chart

4. What Do These Letters Mean?! • H= dominant allele Huntington’s Disease; h=recessive allele no Huntington’s Disease • Phenotype – what you see HH= Huntinton’s Disease is present Hh= Huntington’s Disease is present ( also there is a no Huntington’s Disease carrier) hh= no Huntington’s Disease • Genotype – what is in the genes HH= Homozygous dominant(Huntington’s Disease) Hh= Heterozygous dominant(Huntington’s Disease) hh= Homozygous recessive(no Huntington’s Disease)

5. Genotype and Phenotype Probability • Phenotype: • Ratios: • 3 HG: 1 no HD • Percentages: • 75% HD: 25% no HD • Genotype: • Ratios: • 1HH : 2Hh : 1hh • Percentages: • 25%HH : 50%Hh : 25%hh H h H h

6. Student Practice Phenotype: Ratio: Percentage: Genotype: Ratio: Percentage: H H 4 HD : 0 no HD 100% HD :0% no HD H HH HH 2HH : 2Hh 50%HH: 50%Hh h Hh Hh