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What else can I help you with?
How is sickle-cell disease a representation of codominance?
It's not sickle-cell itself, but rather being a heterozygous carrier of the disease. People with one dominant and one recessive allele for the disease are immune to malaria without the crippling effects of having sickle-cell anemia. I don't think that it can even represent codominance, though.
What causes sickle cell allele?
The sickle cell allele is caused by a mutation in the HBB gene, which encodes a protein called hemoglobin. This mutation causes an abnormal form of hemoglobin (HbS) to be produced, leading to the characteristic sickle shape of red blood cells in individuals with sickle cell disease.
For sickle-cell disease assume S is the dominant allele and s the recessive allele Which genotypes are possible for offspring of a carrier (Ss) and a person who lacks the sickle-cell allele (SS)?
SS,Ss
Which person on the pedigree could not pass the allele for sickle cell disease to his her offspring?
V
Is there any genotype that is SC?
Yes, the genotype SC refers to individuals who have inherited one sickle cell allele (S) and one C allele, resulting in a sickle cell trait that is different from having sickle cell disease. This genotype can lead to some symptoms similar to sickle cell disease under certain conditions.
Can a person who has been successfully treated for sickle cell disease still transmit the disease-causing allele to offspring?
Sickle-cell anemia can only be transmitted if both partners have the disease.
The genetic disorder sickle cell disease is an example of heterozygous dominance?
Sickle cell disease is an example of codominance, not heterozygous dominance. In individuals who are heterozygous for the sickle cell allele, they exhibit a milder form of the disease called sickle cell trait, which demonstrates codominance of the normal and mutant hemoglobin alleles.
Is caused by a mutated allele that produces a defective form of the protein hemoglobin.?
False, Sickle Cell Disease :))
Can give example about overdominance?
Overdominance is when the heterozygote has an advantage over both the recessive and dominant homozygotes. Sickle cell disease is an example of this. When the individual is homozygous for the sickle cell allele, sickle cell disease is shown. When the the individual is homozygous for the wildtype allele, they appear normal. However, when the individual is heterozygous, he or she appears normal and will also be resistent to malaria.
What was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population?
The absence of the selection pressure malaria. Without selection, in the form of the malarial environment, the sickle cell allele will be lost in the overall US population. Even the heterozygous condition is somewhat deleterious and, statistically without malarial selection pressure the allele will be selected out.
Why heterozygous for sickled cell anemia are resistant to malaria?
Because individuals who inherit the gene from only one parent produce red blood cells which are distorted. This distortion makes the cells unpalatable to malaria parasites, without seriously harming the individual. This tends to protect against malaria and that protection causes selection for this allele. Individuals who get the sickle cell gene from both parents suffer serious distortion of the red blood cells. This protects against malaria, but also reduces the oxygen-carrying capacity of the red cells to a dangerous degree. This causes a disease called sickle-cell anaemia, which causes selection against the gene. In malarial regions a balance is established. When a population with sickle cell alleles moves to an area with effectively no malaria present, the sickle cell alleles are steadily selected against. This shifts the balance steadily towards low levels.
How is the DNA in the Sickle Cell allele different from the normal allele?
Normally, the 6th position of the beta chain of hemoglobin is a Glutamic acid, encoded on the DNA as GAG. The sickle cell mutation has the sequence GTG, resulting in a Valine in the 6th position instead.
