Lecture 2- Flashcards
What is incomplete/ partial dominance?
When neither trait is dominant over the other, thus they both show up in an intermediate form.
What is the function of hexosaminidase?
an enzyme involved in lipid metabolism
What is the threshold effect?
When the phenotype of the individual is normal even though there is a mutation or error in their genes.
Define codominance
When both alleles/ genes are dominant, they they both are expressed within the phenotype of the individual
What is Tay-Sachs disease (TSD)?
A recessive disorder that causes non-recoverable damage to the nervous system
Are infants with Tay -Sachs disorder affected at birth?
no, they are unaffected at birth and will develop normal until the age of 6 months
Describe the development of Tay-Sachs disease?
Infants at birth are unaffected until 6 months later. They will begin to lose their mental and physical abilities, and will eventually become blind, deaf, mentally retarded and paralyzed within a year or two.
When do individuals with Tay-Sachs disease die?
5 years old or younger
What causes TSD?
The loss of the activity of hexosaminidase (an enzyme)
Where is hexosaminidase found?
within lysosomes within cells
What is the function of hexosaminidase?
breakdown ganglioside (GM2)
What is ganglioside?
a lipid which makes up nerve cell membranes
What happens when hexosaminidase is not functioning?
The gangliosides will accumulate in the neurons within the brain–> deterioration of the nervous system
What happens to the individual if they are heterozygous for Tay-Sachs disorder?
The individuals body will make about 50% normal hexosaminidase. The individual will not show any symptoms of the disorder as one normal gene is enough to allow the individual’s nervous system to function and
Where is the gene that causes TSD located?
Chromosome 15, it codes for the alpha subunit of Hexosaminidase enzyme
