Huntington’s Disease! Hamza Khan Jeremy Tague Period 2 January 29, 2010

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.

Location Located in the Autosomal Chromosome Not a Sex Chromosome (Not X-Linked) Localized on the 4 th Autosomal chromosome pair. Chromosome #4 Located in every chromosome except for sex chromosomes

Mode of Inheritance Inherited disease (Autosomal Dominant) From parent to child Each child has 50% chance of inheriting the disease If child does not develop disease they cannot pass it on to later generation.

Alleles Each person has 2 alleles per gene. We represent dominant alleles by a capital letter We represent recessive alleles by a small letter HH means they have 2 bad genes Hh means they have 1 bad gene, and 1 good gene hh means they have 2 good genes

Punnett Squares Ratio of the chance of offspring inheriting Huntington’s Disease; ratio determined by parents Each punnett square represents the chances PER CHILD Hhhh Hhhh Hh h h Mother Father HHHh hh Hh H h heterozygous dominant homozygous recessive homozygous dominant

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 HHHh hh Hh H h Percentages Pie Chart

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)

Genotype and Phenotype Probability Phenotype: – Ratios: 3 HH: 1 no HH – Percentages: 75% HH: 25% no HH Genotype: – Ratios: 1HH : 2Hh : 1hh – Percentages: 25%HH : 50%Hh : 25%hh HHHh hh Hh H h

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

Pedigree Circle: Male Square: Female All Blue: Homozygous Recessive. No bad gene. Person has no disease All Green: Homozygous Dominant. Two bad genes. Person has the disease Blue/Green: Heterozygous Dominant. 1 bad gene and 1 good gene. Person carries the bad gene and can pass it one, but is not infected.

STUDENT PRACTICE! Circle: Male Square: Female: Red: White: Red/White: Homozygous Recessive Homozygous Dominant Heterozygous Dominant QUESTIONS! 1. What do you call a half white/half red gene? 2. What genes must the parents have in order for a child to be homozygous Recessive? 3. What are all the possibilities of children can two Homozygous Dominant parents have?