Name: Olivia Taylor, Julia Dudkiewicz, and
Date: January 28, 2010
While viewing the following
presentation please be
Is an inherited disease that makes the host unable to metabolize
galactose. Galactose is a simple sugar found in ½ of milk.
People with Galactosemia either don’t have, or lack the enzyme
(GALT) that helps break down galactose.
Infants that inherit Galactosemia who are feed dairy/milk products,
jaundice, vomiting, lethargy, and also mental retardation, cirrhosis,
and kidney failure can occur.
Children with Galactosemia have lower (IQ) levels then their
Ovarian failure may occur in girls, and that most girls with it
can’t conceive naturally. Though boys have normal testicular
.Galactosemia gene is located on the
How do you get this disorder?
Autosomal recessive pattern
To get this disorder, a child must get one defective gene from each parent
If the child inherits one normal & one bad gene, they are okay. But can still pass
the bad one to their kids. This gives their child another possibility of having
What’s an Autosomal Recessive?
Is when a child has to get a copy of a gene from each parent to have that trait
What’s an Autosomal Dominant?
Is when a child has to only get one defected gene from one parent to inherit a
What’s Sex linked/X-linked?
Is when a gene gets carried on a sex chromosome, especially an x-chromosome
Determines sex & sex characteristics
Alleles are represented by a small letter on the punnett square.
-Capital letters are dominant, and lower case letters are recessive.
• Alleles are a way to identify in a gene pair, which gene produces what
phenotypes. You get them from your parents
• Depending on the disease a small letter (Alleles) can be good or bad
genes. In our disease it is bad.
• Example: In order to have Galactosemia you need two bad genes, or two
small Alleles, or recessive(aa) genes. Having two of the same genes (aa) is
called a homozygous pair. To be a carrier you need a dominant and a
recessive gene (Aa), having a bad and a good genes is called a
Punnett squares to show the possibility of each child
receiving the galactosemia gene
• gg= homozygous recessive (has the complete Galactosemia gene)
• GG= homozygous dominant (does not have the gene at all)
• Gg= heterozygous dominant (Has a carrier of the gene but it does not
• Remember each punnett square is the possibility for EACH child to get
the Galactosemia gene!
• The Father is on the top of the punnett square and the mother is on
the left of the punnett square.
Punnett Square to explain probability with
Ratios, and Percentages.
Heterozygous dominant Homozygous recessive
• If you add them up they should = 4 because there are
only 4 possibilities
• PercentagesHomozygous dominant Heterozygous dominant Homozygous recessive
All the percentages added must equal 100%, because there
are four boxes each representing 25%
Here we use the punnett squares to show what
we can see and what is in our genes
What each letter represents
G is the dominant allele
g is the recessive allele
Phenotype is what we would see
GG = No Galactosemia gene
Gg = No Galactosemia gene
gg = Galactosemia gene
Genotype is what is in our genes
GG is Homozygous dominant (no Galactosemia gene)
Gg is Heterozygous dominant (carrier of
gg is homozygous recessive (Galactosemia gene)
Using Punnett Square
Mo t he r
•Ratios: 2 no Galactosemia: 2 Galactosemia
•Percentages: 50% no Galactosemia: 50%
•Ratios: 2 Gg (heterozygous dominant): 2 gg (homozygous recessive)
•Percentages: 50% Gg: 50% gg
•Ratio: 1 Homozygous Dominant: 2 Heterozygous Dominant :1 Homozygous Recessive:
•Percentage: 25% Homozygous D : 50% Heterozygous Dominant : 25% Homozygous
•Ratio: 3 no Galactosemia: 1 Galactosemia
•Percentage: 75% no Galactosemia: 25% Galactosemia
All Orange :Person has two
bad genes; has Galactosemia
All white: Person may be a
carrier of disorder, but is fine.
All White: Person is a carrier
All Orange: Person has the
disease, has two bad genes
1. In generation I, when the parents have children, which is not possible. For the
children to have the Galactosemia or not to have Galactosemia? Explain.
2. In generation II to the right, what is the percentage of their child not carrying
any Galactosemia gene?
3. In generation 3 to the left, if one of the males mated with an homozygous
recessive person what all of the possibilities of the offspring of what their
children might be?