Please be kind. A harsh genetic disorder is no one’s choice. Keep all comments about any pictures to yourself. Thank you.
Albinism Raashmi Patalapati, Rizzlyn Melo, Erica Price February 1, 2010 Period 3
What chromosome is Albinism located on? • Three different types of albinism: ü OCA-1, OCA-2, and OCA-3 • OCA-1: occurs on chromosome 11 • OCA-2: occurs on chromosome 15 • OCA-3: occurs on chromosome 9
Summary of Albinism Inherited disorder Too little, or complete lack of, melanin Shows very pale, white skin and hair. Causes eyes to appear pink as well as creates eye problems. Can occur in humans, animals, or plants.
Mode of Inheritance The three types of albinism are acquired through the chromosomes. It is an autosomal recessive disorder. Autosomal recessive means that in order to show the disease you must have two of the recessive alleles. Two copies of the gene must be mutated. There is a equal chance of males and females showing and carrying albinism
Alleles • Each person has two alleles per gene • One comes from the mother, the other from the father • Dominant and recessive alleles are represented by letters. • Dominant- capital letter • Recessive- lowercase letter • Dominance is when the allele is able to take over recessive alleles. • Recessiveness is when the allele can be taken over by a dominant allele.
Punnett Squares • Punnett squares represent a particular cross of the parent’s genes to predict the reproduced outcome. • Mother is on the left and father is represented on the top. a aa aa aa A AA Aa aa A aa a Aa aa A Aa Aa a aa aa
Probability and Punnett Squares • Ratios -2 Aa: 2 aa aa A • Percentages - 50% Aa: 50% aa a Aa Aa a aa aa
Letters in Punnett Squares • What these letter mean! AA? Aa? aa? If A represents the normal healthy allele and a represents the recessive albino allele, then we can assume that: • Phenotype a aa A Aa Aa a aa aa AA= doesn’t show Aa= doesn’t show aa= shows • Genotype AA= not a carrier Aa= carrier aa= carrier
Punnett Squares(cont. ) • Phenotype -Ratios- 2 shows: 2 doesn’t show - Percentages- 50% shows : 50% doesn’t show • Genotype - Ratios- 2 Aa: 2 aa - Percentages- 50% carries, but doesn’t show: 50% carries and shows 100% carries
Student Practice Punnett Square Practice Father’ genes: AA; Mother’s genes: Aa M o t h e r ’ s g e n e s Father’s genes A A Genotype: Ratio: 4 carriers Percentage: 100% carriers a Aa Aa Phenotype: Ratio: 4 doesn’t show a Aa Aa Percentage: 100% doesn’t show
3 -generation Pedigree Chart *Autosomal Recessive Key Square: male Circle: female White= Person is fine. May possibly carry the recessive “bad gene. ” Can have one “health” and one “bad” gene of two “healthy genes. ” Black= Person is affected. Has 2 “bad” genes. I II III
Student Practice Key: circle=female square=male shaded in=infected not shaded in=carrier dot= healthy I II III 1. 2. 3.
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