COLOR BLINDESS

By John Daniel “JD” Fogarty and Jude Kweku PokuJanuary 28Period 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

What numbers do you see?

Normal Person Answers:74629No number at all!

Color blindness chromosome

Color 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.

GG GgGg gg

Gg

G g

Mom

Dad

Punnett square probability

Ratios: 1: 2:

1 1 GG 2 Gg

1gg Percentages: 25%: 50%

25% 25% GG 50% Gg

25% gg

GG Gg

Gg gg

G

g

G g

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.

GG Gg

Gg gg

G

g

G g

PHENOTYPES: WHAT YOU SEEGG=REDGg=RED (Green Gene Carrier)gg= Green

GENOTYPES: WHAT IS IN THE GENESGG= Homozygous dominant (RED)Gg= Heterozygous dominant (RED with Green)gg= Homozygous recessive (Green)

Punnett Squares genotypes and phenotypes

Phenotype: Ratio: 3 RED:1 Green Percentages: 75%

RED:25% Green Genotype: Ratio: 1 GG:2 Gg:1 gg Percentages: 25% GG:

50% Gg: 25% gg

GG Gg

Gg gg

G

g

G g

More Punnett squares!

AA AAAa aa

A AAa

TT TTTt tt

T tTt

XX XyXy xy

X yXx

Practice time!Genotype:Ratio: 1XX:2Xy:1xyPercent: 25% XX:50%Xy:25%xyPhenotype:Ratio: 2 RED:2 GreenPercent: 50% RED:50% Green

X yXx

Total Percentage for color blindness:

50%

XyXX

Xx xy

Pedigree of Color blindness

Pedigree PracticeI

II

III

Key:circle-not colorblind malesquare-female without colorblind genecircle with line-colorblind malesquare 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.

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