Question

Q5.1. Which of the following is FALSE? If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection. Natural selection does not favor individuals who are homozygous for the sickle- cell allele, because these individuals typically die before they are old enough to reproduce. Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell disease persists in wetter, mosquito-prone regions in Africa • In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HBA).

Answer 1

Answer-

According to the given question-

Sickle cell disease generally affected the hemoglobin found in the red blood cells that are responsible for carrying the oxygen to cells of the body. here the individuals that are affected with this disease are have crescent or sickle  shape hemoglobin known as hemoglobin S. sickle cell disease is due to the Mutations in the HBB gene which code for beta-globin of haemoglobin and leads to  hemoglobin S or HbS and it was inherited as an autosomal recessive disease.

Now considering each options one by one-

• If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection- this statement is true because if a disease is responsible for reducing fertility then the effect of this disease in their offspring is decreases and if disease is not offering any  advantage it will after some times disapper from the populations due to the natural selection which is not responsible for acting it.
• Natural selection does not favor individuals who are homozygous for the sickle-cell allele, because these individuals typically die before they are old enough to reproduce.-  this statement is true because the humans have two copy of sickle cell allele which are resistant to malaria but due to the breakdown of hemoglobin rapidly in sickle cell anemia causes the mortality.
• Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell disease persists in wetter, mosquito-ridden regions in Africa. this statement is true because the individuals of Africa have   heterozygous HbA/HbS genotype due to presence of favorable conditions in the for the growth and development of mosquito and the natural selection also play an important role for this protection.

• In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA).this statement is false because the the individuals who have copy of sickle cell allele which are resistant to malaria but due to the breakdown of hemoglobin rapidly in sickle cell anemia causes the mortality and the fitness advantage does not help for those who have heterozygous HbA/HbS.