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Galactosemia - PowerPoint PPT Presentation

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Galactosemia. Name: Olivia Taylor, Julia Dudkiewicz, and Varsha M. Date: January 28, 2010 Period: 3. While viewing the following presentation please be respectful Thank you . Summary of Galactosemia.

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Name: Olivia Taylor, Julia Dudkiewicz, and Varsha M.

Date: January 28, 2010

Period: 3

Summary of galactosemia
Summary of Galactosemia respectful

  • 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.

Did you know
Did you know??? respectful

  • Children with Galactosemia have lower (IQ) levels then their siblings

  • Ovarian failure may occur in girls, and that most girls with it can’t conceive naturally. Though boys have normal testicular function.

Mode of inheritance
Mode of Inheritance respectful

  • 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 Galactosemia.

  • 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 disease

  • What’s Sex linked/X-linked?

  • Is when a gene gets carried on a sex chromosome, especially an x-chromosome

    • XX- Female

    • XY-Male

    • Determines sex & sex characteristics

What are alleles
What are Alleles respectful

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 Heterozygous pairs.

Punnett squares to show the possibility of each child receiving the galactosemia gene
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 show)

  • 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
Punnett Square to explain probability with Ratios, and Percentages.

  • Ratios-


    Homozygous dominantHeterozygous dominantHomozygous recessive

  • If you add them up they should = 4 because there are only 4 possibilities

  • Percentages-

    Homozygous dominantHeterozygous dominant Homozygous recessive

    25%50% 25%

    GG Gg gg

  • All the percentages added must equal 100%, because there are four boxes each representing 25%

What each letter represents Percentages.G is the dominant allele g is the recessive allelePhenotype is what we would seeGG = No Galactosemia geneGg = No Galactosemia gene gg = Galactosemia geneGenotype is what is in our genesGG is Homozygous dominant (no Galactosemia gene)Gg is Heterozygous dominant (carrier of Galactosemia gene)gg is homozygous recessive (Galactosemia gene)

Here we use the punnett squares to show what we can see and what is in our genes


Mo t he r


Mo t he r

Using punnett square
Using Punnett Square Percentages.


  • Phenotype:

    • Ratios: 2 no Galactosemia: 2 Galactosemia

    • Percentages: 50% no Galactosemia: 50% Galactosemia

Mo t he r

  • Genotype:

    • Ratios: 2 Gg (heterozygous dominant): 2 gg (homozygous recessive)

    • Percentages: 50% Gg: 50% gg

G Percentages.




  • Genotype:

    • Ratio: 1 Homozygous Dominant: 2 Heterozygous Dominant :1 Homozygous Recessive:

    • Percentage: 25% Homozygous D : 50% Heterozygous Dominant : 25% Homozygous Recessive

  • Phenotype:

    • Ratio: 3 no Galactosemia: 1 Galactosemia

    • Percentage: 75% no Galactosemia: 25% Galactosemia

Pedigree Percentages.

Autosomal recessive


Autosomal Recessive

All Orange :Person has two bad genes; has Galactosemia gene.

All white: Person maybe a carrier of disorder, but is fine.

Student practice
Student Practice Percentages.


Circle: Female

Square: Male

All White: Person is a carrier

All Orange: Person has the disease, has two bad genes



  • 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.

  • In generation II to the right, what is the percentage of their child not carrying any Galactosemia gene?

  • 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?