Presentation on theme: "Cutie dwarf! Dwarfism A genetic disorder that affects bone growth. Some characteristics include: - a long narrow torso - short limbs - unusually flexible."— Presentation transcript:
Dwarfism A genetic disorder that affects bone growth. Some characteristics include: - a long narrow torso - short limbs - unusually flexible limbs - limited rotation of the elbows and hips - a small hump on the mid to lower back (it goes away later in life) - big head (because of the enlarged brain)
OOn the short arm of Chromosome four ›P›Proteins are coded for here. These proteins are for growth (fibroblast growth factor receptor 3) Right there!!(:
80% of documented cases are not inherited. They are simply a new mutation to Chromosome 4. The other 20% is inherited from the parents. If one parent has Achondroplasia, the chances of the offspring getting it is 50% If both parents have Achondroplasia, the chances of the offspring having it is a 50%. There is a 25% chance of the child being normal and a 25% chance of the child having homozygous Achondroplasia (the most severe case. It is when both bad genes come from the parents. Usually causes death).
Alleles You get one allele from your mommy and one allele from your daddy. they come from the sex cells. (ova and sperm) Our alleles are D (dominant) and d (recessive). Dominant: always overpowers the recessive gene Recessive: you get the this gene only when there is no dominant allele present.
DDDd dd Mommy D d Daddy D d dd Daddy d Mommy D d dd DD The Punnett Squares Mommy d Mommy D Daddy D Daddy d Homozygous dominant Heterozygous dominant Homozygous recessive
Ratio and Percentage- 1:2:1 or 25%:50%:25% (Homozygous dominant: Heterozygous dominant: Homozygous recessive) 1:3 or 25%:75% (Heterozygous dominant: Homozygous recessive) 4 or 100% (All Homozygous recessive) 4 or 100% (All Homozygous dominant) DDDd dd Dddd DD
What Does All This Mean? A capital D means that the gene is dominant and a lower case d means it is recessive. Phenotype: – DD- a person with this gene will be a dwarf. So, you will see a person 4’10” and under. – Dd(x2)- a person with this gene will also be a dwarf. – dd- a person with this gene will not be a dwarf. They will live normal lives. Genotype: – DD- Homozygous dominant(a dwarf) – Dd(x2)- Heterozygous dominant(a dwarf) – dd- Homozygous recessive(not a dwarf) DDDd dd
Student Practice Daddy’s Genes Mommy’s Genes (Genes) Genotype: -Ratio: -Percentage: (Physical) Phenotype: -Ratio: -Percentage: DD Dd dd 3:1 75% dwarf: 25% not dwarf 1:2:1 25% DD: 50% Dd: 25% dd D dD d
Pedigree- Autosomal Dominant Circle: female Square: male All White: homozygous recessive gene: a person has 2 “healthy” genes All Green: homozygous dominant: this person has achondroplasia(2 “bad” genes. Half Green/Half White: person has achondroplasia. The dominant gene takes over. Half “good” gene and half “bad” gene.
Student Practice Circle= Square= Shaded in= Not shaded in= Half shaded in= I II III 1.What do you think will be in the next generation? 2.What would happen if both of the starting parents had the “bad” gene? 3.What type of pedigree is this? Female Male Bad Gene Good Gene Half bad half good gene Autosomal Dominant StephBrad Pitt JeffDasiaVenturaEmmaJennMatt KylieMatthew Gabby Gabi JosueJessYvensonVivekJanice LorenaLukeSteffy