Download COLOR BLINDESS

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
 What
numbers do you see?
Normal Person
Answers:
74
6
29
No 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.
Dad
Mom
G g
G GG Gg
g Gg gg
Punnett square probability
G
g
GG
G
1
g Gg
Gg
 Ratios:
 1:
1
2:
2 Gg
GG
1gg
 Percentages:
 25%:
50%
 25% GG
50% Gg
gg
25%
25%
gg
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.
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)
G
g
G GG
Gg
Gg
gg
g
Punnett Squares genotypes and phenotypes
G
g
3 RED:1 Green
G GG
 Percentages: 75% RED:25%
g Gg
Green
 Genotype:
 Ratio: 1 GG:2 Gg:1 gg
 Percentages: 25% GG: 50%
Gg: 25% gg
Gg
 Phenotype:
 Ratio:
gg
T t
A A
TT TT
T
A AA AA
Tt tt
t
a Aa aa
X y
X XX Xy
x Xy xy
More Punnett squares!
Practice time!
y
X
Xy
XX
X
x
Xx
Total Percentage for color
blindness:
xy
50%
Genotype:
Ratio: 1XX:2Xy:1xy
Percent: 25%
XX:50%Xy:25%xy
Phenotype:
Ratio: 2 RED:2
Green
Percent: 50%
RED:50% Green
Pedigree of Color blindness
Pedigree Practice
I
Key:
circle-not colorblind male
square-female without colorblind gene
circle with line-colorblind male
square with line-female with
colorblind gene
II
III
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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