Download A aa - Albinizms

Please be kind. A harsh
genetic disorder is no one’s
choice. Keep all comments
about any pictures to
yourself. Thank you.
Raashmi Patalapati, Rizzlyn Melo, Erica Price
February 1, 2010
Period 3
• Three different types of albinism:
 OCA-1, OCA-2, and OCA-3
• OCA-1: occurs on chromosome 11
•OCA-2: occurs on chromosome 15
•OCA-3: occurs on chromosome 9
Summary of Albinism
 Inherited disorder
 Too little, or complete lack of, melanin
 Shows very pale, white skin and hair.
 Causes eyes to appear pink as well as
creates eye problems.
 Can occur in humans, animals, or
plants.
Mode of Inheritance
 The three types of albinism are acquired through the
chromosomes.
 It is an autosomal recessive disorder.
 Autosomal recessive means that in order to show the
disease you must have two of the recessive alleles. Two
copies of the gene must be mutated.
 There is a equal chance of males and females showing
and carrying albinism
•Each person has two alleles per gene
•One comes from the mother, the other from the father
•Dominant and recessive alleles are represented by
letters.
• Dominant- capital letter
•Recessive- lowercase letter
•Dominance is when the allele is able to take over
recessive alleles.
•Recessiveness is when the allele can be taken over by a
dominant allele.
•Punnett squares represent a particular cross of the parent’s genes to predict the
reproduced outcome.
•Mother is on the left and father is represented on the top.
a
aa
a
aa
aa
a
aa
aa
A
aa
A
AA
Aa
a
Aa
aa
A
aa
a
Aa
aa
a
Aa
aa
a
aa
A
Aa
Aa
a
aa
aa
•Ratios
-2 Aa: 2 aa
a
aa
A
Aa
Aa
a
aa
aa
•Percentages
- 50% Aa: 50% aa
Letters in Punnett Squares
•What these letter mean! AA? Aa? aa?
If A represents the normal healthy allele and a represents the recessive albino allele,
then we can assume that:
•Phenotype
a
aa
A
Aa
Aa
a
aa
aa
AA= doesn’t show
Aa= doesn’t show
aa= shows
•Genotype
AA= not a carrier
Aa= carrier
aa= carrier
Punnett Squares(cont.)
•Phenotype
-Ratios- 2 shows: 2 doesn’t show
- Percentages- 50% shows : 50% doesn’t show
•Genotype
- Ratios- 2 Aa: 2 aa
- Percentages- 50% carries, but doesn’t show:
50% carries and shows
100% carries
Student Practice
Punnett Square Practice
Father’ genes: AA; Mother’s genes: Aa
M
o
t
h
e
r
’
s
g
e
n
e
s
Father’s genes
A
A
Genotype:
Ratio: 4 carriers
Percentage: 100% carriers
a
Aa
Aa
Phenotype:
Ratio: 4 doesn’t show
a
Aa
Aa
Percentage: 100% doesn’t show
*Autosomal Recessive
Key
Square: male
Circle: female
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.
I
II
III
Student Practice
Key: circle=female
square=male
shaded in=infected
not shaded in=carrier
dot= healthy
I
II
III
1.
2.
3.