Genetics of Sickle Cell Anemia
Genetics of Sickle Cell Anemia
Objectives
• To observe how a disease can act as a selective force
• To describe changes in allele frequencies in a population as a result of a selective force
Hypothesis
The starting ratio of HbA to HbS is 3:1; in a typical population, the Homozygous Dominant Gene would become the standard, but because carrying the Heterozygous version of the allele has an advantage to fighting Malaria it will become the dominant Allele for the population. The HbA/HbS gene will thrive because it helps in the fight against Malaria, turning a typically negative trait into an advantage. The Homozygous Recessive will disappear from the population because either way it has a fatal disease. The Homozygous Dominant has a 50% chance of living, it will continue to populate but the dominant Allele will remain the HbA/HbS Gene. Data Tables
F1 Generation Tally
Sack Total
HbA 28
HbA / HbS 19
HbS 3 F1 Generation Surviving Alleles
Surviving HbA 51
Surviving HbS 19
F2 Generation Tally
Sack Total
HbA 28
HbA / HbS 17
HbS 1 F2 Generation Surviving Alleles
Surviving HbA 47
Surviving HbS 17
Discussion Questions
What happened to the frequency of the HbA allele & the HbS allele over the course of this experiment?
As the experiment progressed, the HbA took a sharp dive but quickly evened out; the HbS followed the very same pattern. I think that if it were to continue, the two allele’s would come much closer to the same number, however the HbA would always outnumber the HbS because it still has a 50% chance of possibility of surviving without the aid of the Sickle Cell Gene.
Will the frequencies continue to change as they did in the first three generations (the parental generation as well as the F1 and F2)? Why or why not?
The frequencies will even out, become less rapid, and find an equilibrium. The first generation took a very sharp dive in frequency, but as with all populations they will even out soon. The HbS
Objectives
• To observe how a disease can act as a selective force
• To describe changes in allele frequencies in a population as a result of a selective force
Hypothesis
The starting ratio of HbA to HbS is 3:1; in a typical population, the Homozygous Dominant Gene would become the standard, but because carrying the Heterozygous version of the allele has an advantage to fighting Malaria it will become the dominant Allele for the population. The HbA/HbS gene will thrive because it helps in the fight against Malaria, turning a typically negative trait into an advantage. The Homozygous Recessive will disappear from the population because either way it has a fatal disease. The Homozygous Dominant has a 50% chance of living, it will continue to populate but the dominant Allele will remain the HbA/HbS Gene. Data Tables
F1 Generation Tally
Sack Total
HbA 28
HbA / HbS 19
HbS 3 F1 Generation Surviving Alleles
Surviving HbA 51
Surviving HbS 19
F2 Generation Tally
Sack Total
HbA 28
HbA / HbS 17
HbS 1 F2 Generation Surviving Alleles
Surviving HbA 47
Surviving HbS 17
Discussion Questions
What happened to the frequency of the HbA allele & the HbS allele over the course of this experiment?
As the experiment progressed, the HbA took a sharp dive but quickly evened out; the HbS followed the very same pattern. I think that if it were to continue, the two allele’s would come much closer to the same number, however the HbA would always outnumber the HbS because it still has a 50% chance of possibility of surviving without the aid of the Sickle Cell Gene.
Will the frequencies continue to change as they did in the first three generations (the parental generation as well as the F1 and F2)? Why or why not?
The frequencies will even out, become less rapid, and find an equilibrium. The first generation took a very sharp dive in frequency, but as with all populations they will even out soon. The HbS