Achondroplasia

1. Achondroplasia Kelly Correia and Alyssa Antonucci January 28, 2010 Hour 3

2. Achondroplasia is… • A genetic condition • Results in abnormally short stature • -> Otherwise known as ‘Dwarfism.’ • has to do with the bones and how they make bone instead of cartilage. What are some symptoms? • a baby will have a relatively long torso and narrow torso and short extremities (arms & legs). • typically have unusually large heads with prominence of the forehead. • baby’s fingers appear short & the ring and middle finger move in different directions, giving the hand a three-pronged (trident) appearance. Did you know… • Achondroplastic dwarfs’ average height is usually four feet 3 inches in males and four feet for females. • There is no treatment for Achondroplasia. • Jyoti Amge from India was diagnosed with Achondroplasia and is the shortest person in the world measuring in at 23 inches tall and weighs 11 pounds.

3. Achondroplasia is located on… Chromosome 4

4. Achondroplasia is inherited… • as an autosomal dominant trait • only a single copy of the abnormal gene is required to cause Achondroplasia. • the chance of a baby being born and diagnosed with this condition has been shown to increase with paternal age, or the age of the father.

5. What are Alleles?! • an Allele is one member of a pair or series of genes that occupy a specific position on a specific chromosome. • We represent dominant alleles with a capital letter, like “R” and we represent recessive alleles with a lowercase letter, like “r”. When these two letters are put together, like Rr, it means the uppercase “R” is the dominant gene and the lowercase “r” is the recessive gene. • You get one Allele from your mother and another allele from your father. You get two alleles for each gene. • If the two alleles for one gene are the same, then the individual is homozygous for that gene. If the two alleles are different then the individual is heterozygous.

6. Punnett Squares Are Fun! Punnett Square 1: Punnett Square 2: f a F A F a A f R r Punnett Square 3: g Punnett Square 4: G g R r G

7. Punnett Square: Probability F f Percentages Homozygous Dominant: 25 % Heterozygous Dominant: 50 % Homozygous Recessive: 25 % F There are four different possibilities. When getting percentage the total has to be 100%. This means that each box represents 25% since 100 divided by 4 is 25. f Ratios Homozygous Dominant :1 GG Heterozygous Dominant: 2 Ff Homozygous Recessive: 1 ff There has to be a total of four combinations in the Punnet Square. There has to be four because that’s the number of possibilities a punnet square can have.

8. Punnet Squares The uppercase F represents the dominant allele. While the lowercase f represents the recessive allele. This is a dominant disorder so even if there is a recessive allele as long as it has another dominant allele , it will remain dominant. Phenotype FF= Dominant allele Ff= Dominant Allele ( with a recessive allele) ff= Recessive allele Genotype FF: Homozygous dominant Ff: Heterozygous dominant ff: Homozygous recessive F f F f

9. Punnet Square Example F f F f Phenotype: Ratio: 3 dominant genes (1 homozygous dominant, 2 heterozygous dominant) , 1 recessive gene (homozygous) Percentage: 75% dominant (25% homozygous dominant, 50% heterozygous dominant) , 25% recessive (homozygous) Genotype: Ratio: 1 FF, 2 Ff, 1 ff Percentage: 25% FF, 50 % Ff, 25% ff

10. Punnett Square Practice Father’s Genes F f M other’s Genes F Genotype: Ratio: 2 FF, 2 Ff Percentages: 50% FF, 50% Ff Phenotype: Ratio: 2 homozygous dominant, 2 heterozygous dominant Percentages: 50% homozygous dominant, 50% heterozygous dominant F

11. 3 Generation Pedigree Autosomal Dominant White= (homozygous recessive) The person doesn’t have any of the bad genes. Half-Blue=The person has 1 bad gene and 1 healthy gene Full blue- (homozygous dominate) The person has both bad genes =Girl =Boy

12. Pedigree Practice Key = Female = Male Light Orange= (homozygous recessive) The person doesn’t have any of the bad genes. Half-Light Half- Dark Orange=The person has 1 bad gene and 1 healthy gene Dark Orange= (homozygous dominate) The person has both bad genes I. II. III. 1.) If the father has both of the bad gene’s and the mother doesn’t have any bad gene’s, how likely will the offspring to be born without any bad genes? 2.) One parent has 1 bad gene and the other parent has one both bad genes of the achondroplasia gene, how likely is the chance of the offspring to have achondroplasia? 3.) If two parents have achondroplasia, how likely is their child to not have achondroplasia?