Final answer:
The correct answer is option 4. The genes responsible for the alpha and beta chains in human hemoglobin, which arose from gene duplication and divergence, are known as paralogous genes (option 4).
Step-by-step explanation:
Human hemoglobin is a protein molecule present in red blood cells that consists of four polypeptide chains: two alpha (α) chains and two beta (β) chains. These chains are produced by two different genes, the alpha-hemoglobin and beta-hemoglobin genes. Given their sequence differences and structural similarities, it is suggested that both genes were produced by a gene duplication event earlier in evolutionary history.
Such genes, which arise from a duplication within the same species and then diverge, are known as paralogous genes. Therefore, in the context of human hemoglobin and its evolutionary origins, the alpha-hemoglobin and beta-hemoglobin genes would be best described as paralogous genes, making the correct option (4) Paralogous genes.
Additionally, abnormalities in hemoglobin, such as in sickle cell anemia, arise due to mutations in the coding region of these genes. Variations in these genes lead to different forms of hemoglobin, like adult hemoglobin (Hb A), which has 2α2β chains, fetal hemoglobin (Hb F) with 2α2γ chains, and minor adult hemoglobin (Hb A₁) with 2α2δ chains.