2. ColorBlindnessColorBlindness Nancy Paguay & Zinani Harriott February 1, 2010 Period 9/10

3. www.toledo-bend.com/colorblind/Ishihara.asp Color blindness (color vision deficiency) is a condition in which certain colors cannot be distinguished. Symptoms  Trouble seeing colors and the brightness of colors in the usual way  Inability to tell the difference between shades of the same colors Treatment  None Some Facts  8% of all men are suffering from color blindness.  John Dalton, who discovered color blindness, was also colorblind himself  Red/green colorblindness is most common

5. InheritanceInheritanceSex-linked –C–Characteristics (phenotype) that are determined by genes carried on the sex chromosomes (X chromosome) Sex-linked recessive Genes are expressed in females only if there are two copies of the gene (one on each X chromosome) Genes are expressed in males, if there is one copy of an X-linked recessive gene on the X chromosome

6. Explain what alleles are. How many alleles does each person have per gene Where they come from How we represent recessive or dominant alleles -RR, rr, Rr What is dominance and recessiveness? Sex linked (x-linked) is represented with X R, or X r, or Y

7. Make a punnett square to demonstrate the probability per child depending on the parents Make more than one punnett square. Parents determine the ratio of probability of offspring having the genetic disorder. Explain(see below) to the class how the punnett square works. Female is on the left and father is represented on the top. *** Each punnett square represents the probability PER CHILD. Not all of the children parents may have. *** homozygous dominant heterozygous dominant homozygous recessive

8. Use the same punnett square model to… Explain probability using: Ratios (must equal 4 because there are 4 possibilities) Percentages (must equal 100 because there are 4 possibilities 25% each) 1:2 : 1 1GG : 2Gg : 1gg 25% : 50% :25% 25%GG : 50%Gg : 25%gg homozygous dominant : heterozygous dominant : homozygous recessive

9. Use the same punnett square to use as your model to explain… What these letter mean! GG? Gg? gg? Phenotype (what you SEE) GG= GREEN Gg= GREEN (yellow gene carrier) gg = yellow Genotype (what is in the GENES) GG= Homozygous dominant (GREEN) Gg= Heterozygous dominant (GREEN) gg = homozygous recessive (yellow) If G represents the dominant allele GREEN and g represents the recessive allele yellow, then we can assume that:

10. Use the same punnett square model to… Explain Genotype and Phenotype probability using: Phenotype -Ratios- 3 GREEN : 1 yellow - Percentages- 75% GREEN : 25% yellow Genotype - Ratios- 1GG : 2 Gg : 1 gg - Percentages- 25% GG: 50% Gg : 25%gg

11. Student Practice Punnett Square Practice Y ou provide genes for the students: only parents and student fill in the box genotypes and phenotypes Genotype: Ratio: Percentage: Phenotype: Ratio: Percentage: -When the students are finished, ask them to share their answers with you. Use the custom animation option to hide the answers until student s have shared theirs with you.

12. Lastly, a 3 generation hypothetical Pedigree Circle = female Square = male All White= homozygous recessive gene, person is fine, has 2 copies of the “healthy” gene All Green= homozygous dominant, person have disorder and 2 copies of the “bad” gene Half Green/Half White= because this is a dominant disorder (rules of dominance), the person has the disease and only has one copy of the “bad” gene and one copy of the “healthy” gene. Autosomal Dominant Autosomal Recessive 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. X-linked Color gene is “bad” on x chromosome Color gene is “healthy” on x chromosome One gene is “bad”, one gene is “healthy” on the x chromosome Female is fine. 3 generations, (I: two parents II: 3 children and two spouses III: 4 children, any combo ( explain how to READ your punnett square)

13. Student Practice (you provide generation I, 2, and 3) Show a pedigree like this, but you fill in the rest using a different sample than the previous page. You choose male and female, who is married to who (you have to add 2 spouses, and who has children in the Generation III. I II III Example: ***Ask 3 questions (type them on this page) to make sure the students can analyze a pedigree. (NO yes/no answers) 1. 2. 3. Example: ***Make a key: circle= square= shaded in= not shaded in= half shaded in=