1). The inheritance of recessive genes (disease causing) can remain prevalent if presence of two copies of an allele is disadvantageous and presence of one copy of the allele may be advantageous. For example in case of sickle cell anaemia, two alleles may cause sickle cell anaemia but carrying one allele is advantageous in regions where malaria is common because this single copy of allele offers resistance against malaria. Thus, many people still carry the allele of sickle cell anaemia, as natural selection does not remove it; this is called “balanced polymorphism.” Thus, people carrying one copy of sickle cell disease causing allele migrated to the regions of Africa and develops resistance to malaria parasite. They passed this protective allele to their offspring. However, two carriers with protective allele might have a child with sickle cell disease. Today, the prevalence of malaria parasite is decreased well by artificial control methods. This change in climate caused decreased number of sickle cell allele carriers. 2). Yes, the individuals homozygous for the mutation are susceptible for the sickle cell anemia, whereas the heterozygous individuals are resistant to malaria. 3). Increased incidence of malaria causes the persistence of sickle cell allele as it increases the fitness of an individual. Solution 1). The inheritance of recessive genes (disease causing) can remain prevalent if presence of two copies of an allele is disadvantageous and presence of one copy of the allele may be advantageous. For example in case of sickle cell anaemia, two alleles may cause sickle cell anaemia but carrying one allele is advantageous in regions where malaria is common because this single copy of allele offers resistance against malaria. Thus, many people still carry the allele of sickle cell anaemia, as natural selection does not remove it; this is called “balanced polymorphism.” Thus, people carrying one copy of sickle cell disease causing allele migrated to the regions of Africa and develops resistance to malaria parasite. They passed this protective allele to their offspring. However, two carriers with protective allele might have a child with sickle cell disease. Today, the prevalence of malaria parasite is decreased well by artificial control methods. This change in climate caused decreased number of sickle cell allele carriers. 2). Yes, the individuals homozygous for the mutation are susceptible for the sickle cell anemia, whereas the heterozygous individuals are resistant to malaria. 3). Increased incidence of malaria causes the persistence of sickle cell allele as it increases the fitness of an individual..

1. 1). The inheritance of recessive genes (disease causing) can remain prevalent if presence of two
copies of an allele is disadvantageous and presence of one copy of the allele may be
advantageous.
For example in case of sickle cell anaemia, two alleles may cause sickle cell anaemia but
carrying one allele is advantageous in regions where malaria is common because this single copy
of allele offers resistance against malaria. Thus, many people still carry the allele of sickle cell
anaemia, as natural selection does not remove it; this is called “balanced polymorphism.”
Thus, people carrying one copy of sickle cell disease causing allele migrated to the regions of
Africa and develops resistance to malaria parasite. They passed this protective allele to their
offspring. However, two carriers with protective allele might have a child with sickle cell
disease.
Today, the prevalence of malaria parasite is decreased well by artificial control methods. This
change in climate caused decreased number of sickle cell allele carriers.
2). Yes, the individuals homozygous for the mutation are susceptible for the sickle cell anemia,
whereas the heterozygous individuals are resistant to malaria.
3). Increased incidence of malaria causes the persistence of sickle cell allele as it increases the
fitness of an individual.
Solution
1). The inheritance of recessive genes (disease causing) can remain prevalent if presence of two
copies of an allele is disadvantageous and presence of one copy of the allele may be
advantageous.
For example in case of sickle cell anaemia, two alleles may cause sickle cell anaemia but
carrying one allele is advantageous in regions where malaria is common because this single copy
of allele offers resistance against malaria. Thus, many people still carry the allele of sickle cell
anaemia, as natural selection does not remove it; this is called “balanced polymorphism.”
Thus, people carrying one copy of sickle cell disease causing allele migrated to the regions of
Africa and develops resistance to malaria parasite. They passed this protective allele to their
offspring. However, two carriers with protective allele might have a child with sickle cell
disease.
Today, the prevalence of malaria parasite is decreased well by artificial control methods. This
change in climate caused decreased number of sickle cell allele carriers.
2). Yes, the individuals homozygous for the mutation are susceptible for the sickle cell anemia,
whereas the heterozygous individuals are resistant to malaria.

2. 3). Increased incidence of malaria causes the persistence of sickle cell allele as it increases the
fitness of an individual.