huntington’s disease! hamza khan jeremy tague period 2 january 29, 2010
TRANSCRIPT
Huntington’s Disease!
Hamza KhanJeremy Tague
Period 2January 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 4th 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
Hh hhHh hh
H h
h
h
MotherFather
HH HhHh hh
H h
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 recessiveex: 1 : 2 : 1ex: 1HH : 2Hh : 1hh
• Percentages:– Must equal 100; each possibility equals
25%– Put percentages into the ratioex: 25% : 50% : 25%ex: 25%HH : 50%Hh : 25%hh
HH HhHh hh
H hH
hPercentages Pie Chart
What Do These Letters Mean?!
• H= dominant allele Huntington’s Disease; h=recessive allele no Huntington’s Disease
• Phenotype – what you seeHH= 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 genesHH= 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
HH Hh
Hh hh
H h
H
h
Student Practice
Phenotype:Ratio:
Percentage:
Genotype:Ratio:
Percentage:
H H
H
h
HH HH
Hh Hh
4 HH: 0 no HH 100% HH :0% no HH
2HH : 2Hh
50%HH: 50%Hh
PedigreeCircle: 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 DominantQUESTIONS!
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?