COLOR BLINDESS

By John Daniel “JD” Fogarty and Jude Kwaku PokuJanuary 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

What numbers do you see?

COLOR BLINDNESS CHROMOSOME

Color blindness is X-linked recessive in the mother’s chromosome. It is more common in males than females.

MODE OF INHERITENCE

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 carry of the defect.

ALLELES

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

1ggPercentages: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 GreenPercentages: 75% RED:25% GreenGenotype:Ratio: 1 GG:2 Gg:1 ggPercentages: 25% GG: 50% Gg:

25% gg

GG Gg

Gg gg

G

g

G g

MORE PUNNETT SQUARES!

AA

AA

Aa 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

XX XyXy xy

X yXxTotal Percentage for color blindness:

50%