Transcript A aa - Albinizms

Raashmi Patalapati, Rizzlyn Melo, Erica Price
February 1, 2010
Period 3
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.
• 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
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 higher chance of a male showing 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.
•Female 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:
Percentage:
Phenotype:
Ratio:
Percentage:
-When the students are finished, ask
them to share their answers with you.
Use the custom animation option to hide
the answers until student
theirs with you.
s have shared
Autosomal Dominant
Circle = female
Square = male
All White= homozygous recessive gene, person
is fine, has 2 copies of the “healthy” gene
All Green= homozygous dominant, person
have disorder and 2 copies of the “bad” gene
Half Green/Half White= because this is a
dominant disorder (rules of dominance), the
person has the disease and only has one copy of
the “bad” gene and one copy of the “healthy”
gene.
Autosomal Recessive
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.
Color gene is “bad” on x chromosome
Color gene is “healthy” on x chromosome
Color gene is “healthy” on x chromosome
One gene is “bad”, one gene is
“healthy” on the x chromosome
Female is fine.
3 generations, (I: two parents II: 3 children and two spouses III: 4 children, any combo
( explain how to READ your punnett square)
Student Practice
(you provide generation I, 2, and 3)
Show a pedigree like this, but you fill in the rest using a different sample than the previous page.
You choose male and female, who is married to who (you have to add 2 spouses, and who has children in the
Generation III.
I
II
Example:
***Make a key: circle=
square=
shaded in=
not shaded in=
half shaded in=
III
Example:
***Ask 3 questions (type them on this page)
to make sure the students can analyze a
pedigree. (NO yes/no answers) 
1.
2.
3.