Multigene families include two or more nearly identical genes with related functions. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16. Some of these genes produce hemoglobin only in the fetus or embryo. Others are very similar to functional genes, but have accumulated mutations and are no longer functional. The first figure shows the scheme of alpha globin gene family. Alpha globin gene cluster is located on chromosome 16 and includes loci: zeta, pseudozeta, pseudoalpha-2, pseudoalpha-1, alpha-2, alpha-1, pseudotheta. Zeta gene produces hemoglobin in the embryo; alpha-2 and alpha-1 produce hemoglobin in the fetus and adult. The second figure shows the scheme of beta-globin gene family. Beta-globin locus is located on chromosome 11.The order of the genes in the beta-globin cluster is: epsilon, gamma-G, gamma-A, pseudobeta, delta, beta. Epsilon produces hemoglobin in the embryo, gamma-G and gamma-A produce hemoglobin in the fetus. Delta and beta produce hemoglobin in the adult.
What is the most likely mechanism for a gene sequence moving from one chromosome to another?
A. Errors in replication during meiosis followed by deletion of the original sequence in the second meiotic division
B. Multiple recombinations between homologous chromosomes during mitosis
C. Transposition to different chromosomes by the ancestral gene.
D. Crossing over between sister chromatids during meiosis