Figure 1. Model for homologous recombination between 4.2 kb repeats (open boxes) flanking the human glutathione S-transferase M1 (GSTM1) gene leading to gene deletion (Xu et al., 1998). M1, M2, M4 and M5 denote the GSTM1, GSTM2, GSTM4 and GSTM5 genes respectively. Vertical lines denote EcoR I and Hind III restriction sites. The sizes of the EcoR I/Hind III fragments are shown. (Figure from Cooper DN 1999 Human Gene Evolution with the kind permission of BIOS Scientific Publishers, Oxford.)

Figure 2. Examples of deletions flanked by short direct repeats within noncoding sequences of mammalian -globin genes. (From Efstratiadis et al. 1980.) Pairwise alignments of sequences within noncoding regions of mammalian -globin genes are shown. A deletion is assumed in the upper sequence with respect to the lower sequence. Dashes denote the nucleotides not present in the upper sequence. Short direct repeats are underlined. The two aligned human A large intron sequences are those of two different alleles. (Figure from Cooper DN 1999 Human Gene Evolution with the kind permission of BIOS Scientific Publishers, Oxford.)

Figure 3. Alignment of -globin gene sequences from colobus monkey (C), rhesus macaque (R), baboon (B), spider monkey (S) and human (H). (After Vincent and Wilson 1989) Transcribed sequences are denoted by upper case letters, flanking regions are in lower case letters. +1 denotes the site of trancriptional initiation. Underlined bases represent an imperfect inverted repeat which may contribute to the formation of a hairpin loop. (Figure from Cooper DN 1999 Human Gene Evolution with the kind permission of BIOS Scientific Publishers, Oxford.)