The Zebrafish but is fully conserved on the

The first explanation involves
mutation rate within DNA replication between species. In vertebrates, a shorter generation time leads to faster rates of
evolution as replication is more often per unit time. (Bromham et al. 1996). Also, replications per generation vary; in gametes, it takes fewer cell generations to make
Zebrafish ova than Humans. (Bromham and
Leys. 2005). Regarding Figure 7, there is a greater
variety of genes in lower vertebrates, compared to the Human and Mouse that
appear more conserved. An example is the SEMA6D gene which appears in
Zebrafish and Xenopus and novel genes in Chickens and Xenopus. Furthermore,
gene insertions shape genetic diversity and cause a shift in order or introduction of genes, shown in Figure
7 by the addition of GM9913 in the Mouse
genome. 
(Yan, Y., et al. 2014).

Transposition of genes can change
genome size, sequence and expression during speciation and evolution. Transposition
induced changes (stress) can produce alterations once inserted, which include
insertions, translocations and duplications. (Clegg M T., et al. 2003). Furthermore, transposable elements can participate in
re-organisation of the genome, through the mobilisation
of non- transposable elements or as
recombination substrates. This could
result from the homology of two sequences
located on the same/different chromosomes, leading to alterations in the
chromosome. (Kidwell, et al. 2001). In relation to Figure 7,
the region of DUT – SLC12A1 – CTXN2 –
MYEF2 – SLC24A5 is on the left of the FBN1 gene in Zebrafish but is fully
conserved on the right of the gene in Human, Mouse and Chicken. 

Chromosomal translocation can also support the
conservation of single genes between species- not by position but by presence. Chromosomal
rearrangements can include deletions, duplications, translocations and
inversions. These can be caused by DNA double
helices breakage at two locations, followed by re-joining of the ends to
produce a new arrangement of genes, different from the gene order
before. Inversions specifically, are balanced rearrangements so do not
change the amount of genetic material, but the order of the genes. (Griffiths., et
al. 1999). Therefore, implying that each species share the same set
of genes but could be upstream or downstream to the FBN1 gene.