Question

The model of globin gene evolution shown in Figure 21.14 suggests that an ancestral gene is duplicated and mutated to become α- and β-globin genes, and then each one was further duplicated and mutated. What features of the data set to support the model?

Short answer

Hemoglobin disorders are common disorders in humans, and these are also inherited diseases. If any new gene has appeared in the genome during mutation, it eventually develops differences between organisms.

In adults, an alpha-chain of the normal hemoglobin has 141 amino acids, and a beta-chain has 146 amino acids. Changing the number of amino acids will eventually make different proteins.

In the data, A_γand G_y have the highest numbers of amino acids compared to others.

Step-by-step solution

Goblin genes

The Goblin gene has two clusters and is composed of 4 polypeptide chains that are linked together. The goblins consider the superfamily of globular proteins, and these globular proteins have heme in their structures and help in the transportation of oxygen and oxygen binding.

Alpha-globin and beta-globin protein

Both alpha-globin and beta-globin genes are defined as the subunits of hemoglobin.These genes are essential for red blood cells to carry oxygen throughout the human body.

Hemoglobin has four subunits: two alpha-globin subunits and two beta-globin subunits.

In humans, the cluster of an alpha-globin gene is present on chromosome number 16, and the beta-globin gene is present on chromosome number 11 (mainly in its short arm).

Ancestral gene duplication and mutation

In methemoglobinemia, a mutation will occur in the HBB gene, and this mutation will change the beta-globin proteins, and the heme iron will change to ferric by converting ferrous. Due to the alteration, the color of hemoglobin also changes from red to brown color.

Alpha-globin gene mutation will occur in two ways. One is general deletion, and another is non-deletions associated with point mutations, generally deletion of both α+ and α- phenotypes.

Hence, the data table will indicate the change in the number of amino acids in the subunits of the alpha family and beta family. It will support that the ancestral genes’ duplicated and mutated to give rise to alpha and beta genes.