Achondroplasia Taylor Bagen Liam Trampota January 27, 2010 Period 9/10

What is Achondroplasia? Bone growth disorder Has problems converting cartilage to bone Commonly effects arms and legs Average height of someone with Achondroplasia is 4’4 for a male, and 4’1 for a female Characteristics 1.Short arms and legs 2.Restricted elbow movement 3.Macrocephaly, or an “enlarged heard” and prominent forehead 4.Fingers are usually short and the ring finger is commonly far apart from the middle finger. 5.Average intelligence 6.Bowed legs 7.Spinal curve *80% of all achondroplasia cases are due to sporadic mutation, rather than inheritance.

Chromosomal Location Fibroblast Growth Factor Receptor 3 gene or FGFR3. FGFR3 gene is located on the short arm of chromosome 4.

Mode of Inheritance Achondroplasia is an autosomal dominant pattern. Autosomal dominant means that only one copy of the disease is still enough to cause the disorder. This means that both parents could be normal sized, yet if they carry the disease their offspring will also carry the disease. In fact, 80% of people with achondroplasia have normal sized parents. While achondroplasia can be inherited in your genes, the more common way of getting the disease is simply random. Even if both parents do not have the disease, their offspring could get it. However, this is very rare.

Alleles One member of a pair of genes that is located on a specific spot of a chromosome that controls the same trait. (biology online) Each person has one allele from each parent per gene. Recessive and dominant alleles are represented with either capitalized or lowercased letters. RR=dominant, dominant. rr=recessive, recessive. Rr=dominant, recessive. A dominant allele produces it’s trait even if the other allele is recessive. A recessive allele only produces it’s trait if both of the alleles are recessive. Sex linkage determines what gender your child will be. A female is a homozygous link(XX) and a male is a heterozygous link (XY).

Punnett Squares 1rr RRr rrr 2WW wWw w 3Cc CCCCc c cc Punnett Squares: -The female is the column going down on the left, and the father is the column going across to the right. -In Punnett Square 1, the female has the genes Rr and the male has the genes rr. -There are three different kind of outcomes. Homozygous dominant. Homozygous recessive. Heterozygous dominant. *A Punnett Square determines the probability for one child to have any one gene.* When given a dominant allele and a recessive allele you are left with a heterozygous dominant pair. When given two dominant alleles you are left with a homozygous dominant pair. When given two recessive alleles you are left with a homozygous recessive pair. -Homozygous means two of the same alleles. (two dominant or two recessive) -Heterozygous means two different alleles. (one dominant allele, one recessive allele.

Probability 1rr RRr rrr Using Punnett Square 1 let’s figure out the probability for the offspring showing this gene. Ratios: 2:2 Rr rr Percentages: 50%:50% Rrrr *Using the Punnett Square, we can learn the likeliness of which allele will be given to the offspring.

Phenotypeis what you SEE. (think of physical=phenotype, they both start with ph) RR = RED Rr = RED (however, this means that the gene for brown hair is carried) rr = brown Genotypeis what’s in the GENES. (think of genes=genotype, they both start with gen) RR = Homozygous dominant (RED) Rr = Heterozygous dominant (RED) rr= Homozygous recessive (brown) *If R represents the dominant allele RED, and r represents the recessive allele brown… Phenotype vs. Genotype

How to Use Phenotype and Genotype Phenotype Ratio-2 red: 2 brown Percentage-50% red: 50% brown Genotype Ratio-2 Rr: 2 rr Percentage-50%Rr: 50%rr 1rr RRr rrr

Your turn! Tt TTTTt t tt F a ther ’ s G enes Mother’s Mother’s GenesGenes T=tall, t=short Genotype: Ratio-1 TT: 2 Tt: 1 tt Percentages-25% TT: 50% Tt: 25% tt Ratio-3 tall: 1 short Percentages-75% tall: 25% short Phenotype:

Autosomal Dominant Pedigree Male Female The person has the disease but only has one copy of the gene. Homozygous recessive gene, person is fine and has healthy genes *Homozygous dominant gene, person has disorder and two bad genes. (not shown)

Student Practice Male Female One copy of each Homozygous recessive gene 2 2 Homozygous dominant gene Review: 1)Can any homozygous recessive children be formed by a “1” and “2” spouse? Explain why or why not. 2)How many copies of the bad gene does “1” have? 3)What’s the only result possible when “2” and “0” have children?

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