COLOR BLINDESS By John Daniel “JD” Fogarty and Jude Kweku Poku January 28 Period 3
Summary of Color blindness Color Blindness is defined as the inability to distinguish between certain colors. Color Blindness occurs when there is an absence of color-sensitive pigments in the cone cells of the retina, or the nerve layer at the back of the eye. Color Blindness symptoms can vary. Some people may have trouble seeing red, while others may have a difficulty with blue. These kinds of deficiencies are not so serious. For a person who has a full on color deficiency, the only colors they can see are different shades of black, white, and grey.
Color blindness tests WWhat numbers do you see? Normal Person Answers: 74 6 29 No number at all!
Color blindness chromosome CColor blindness is X-linked recessive in the mother’s chromosome. It is more common in males than females.
Mode of Inheritance People acquire the genetic disorder of color deficiency through birth. A color defective male always inherits the deficiency though his mother who usually has normal color vision, but is a carrier of the defect. It is x-linked resecive Sex-linked inheritance means it is carried by a sex chromosome X-linked inheritance means it is situated on the X chromosome Autosomal recessive inheritance is a pattern of inheritance in which both copies of an autosomal gene must be abnormal for a genetic disease to occur Autosomal dominant is a pattern of inheritence in wich both alleles of a gene locus are partially shown often creating an intermediate phenotype
Alleles An allele is one of two or more different forms of a gene that aries by mutation and are found on the same place on a chromosome. Everybody has two alleles per gene. one form mum and one from dad. If it is a dominant allele, it will be represented by a capital letter, and if it is recessive, it shall be represented by a lower case letter. for example, AA, Aa,or aa. With genes, dominance and recessiveness is a big factor, the dominant gene will always triumph over the recessive gene. but if you have two recessive genes, obviously, they will win over no dominant genes. In color deficiency, it would represented as Xr
Punnett squares Punnett squares are used to show the probability of receiving a genetic disorder from a parent. GGGgGg GgGggg G g Gg Mom Dad
What are Punnett squares? Uppercase letters represent dominant genes while lowercase represent recessive genes, which are always over powered by the dominant genes. A red gene represents a gene that is not a carrier of color blindness, while a green gene represents a gene that is a carrier. GGGgGg GgGggg G g Gg PHENOTYPES: WHAT YOU SEE GG=RED Gg=RED (Green Gene Carrier) gg= Green GENOTYPES: WHAT IS IN THE GENES GG= Homozygous dominant (RED) Gg= Heterozygous dominant (RED with Green) gg= Homozygous recessive (Green)
Punnett Squares genotypes and phenotypes PPhenotype: RRatio: 3 RED:1 Green PPercentages: 75% RED:25% Green GGenotype: RRatio: 1 GG:2 Gg:1 gg PPercentages: 25% GG: 50% Gg: 25% gg GGGgGg GgGggg G g Gg
More Punnett squares! AA Aaaa AA A aTTT Tttt Tt T t XXXy xy Xy X x
Practice time! Genotype: Ratio: 1XX:2Xy:1xy Percent: 25% XX:50%Xy:25%xy Phenotype: Ratio: 2 RED:2 Green Percent: 50% RED:50% Green X y X x Total Percentage for color blindness: 50% Xy XX Xxxy
Pedigree Practice I II III Key: circle-not colorblind male square-female without colorblind gene circle with line-colorblind male square with line-female with colorblind gene 1. Aussming the fourth generation on the left will be paired with a female that has the gene for color blindness, what do you predict will happen to their the child if it is a boy? -It will also have color blindness, because both the father and mother have the deficient gene. 2. Based on the chart, why does the third generation male on the left have colorblindness? -He has color blindness, but cause his father has the defeciency, and thus, he had an extreamly high chance of getting it. 3. Where did the female on the right side obtain her deficiant gene from? -It was passed down from her deficient mother.