Transcript Albinism Powerpoint

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.
•Make more than one punnett square. Parents determine the ratio of probability
of offspring having the genetic disorder. Explain(see below) to the class how the
punnett square works.
•Female is on the left and father is represented on the top.
•*** Each punnett square represents the probability PER CHILD. Not all of the
children parents may have. ***
•homozygous dominant
•heterozygous dominant
•homozygous recessive
Explain probability using:
•Ratios
(must equal 4 because there are 4 possibilities)
homozygous dominant:heterozygous dominant:homozygous recessive
1
:
•Percentages
1GG :
2
2Gg
:
:
1
1gg
(must equal 100 because there are 4 possibilities 25% each)
homozygous dominant:heterozygous dominant:homozygous recessive
25%
:
25%GG :
50%
50%Gg
:
:
25%
25%gg
Use the same punnett square to use as your
model to explain…
•What these letter mean! GG? Gg? gg?
If G represents the dominant allele GREEN and g represents the recessive allele
yellow, then we can assume that:
•Phenotype (what you SEE)
GG= GREEN
Gg= GREEN (yellow gene carrier)
gg = yellow
•Genotype (what is in the GENES)
GG= Homozygous dominant (GREEN)
Gg= Heterozygous dominant (GREEN)
gg = homozygous recessive (yellow)
Use the same punnett square model to…
Explain Genotype and Phenotype probability using:
•Phenotype
-Ratios- 3 GREEN : 1 yellow
- Percentages- 75% GREEN : 25% yellow
•Genotype
- Ratios- 1GG : 2 Gg : 1 gg
- Percentages- 25% GG: 50% Gg : 25%gg
Student Practice
Punnett Square Practice
You provide genes for the students:
only parents and student fill in the box genotypes
and phenotypes
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.
X-linked
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.