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692 Chapter 20 NEL

The single nucleotide differences have most likely

resulted from point mutations, while the nine-

nucleotide segment in species Y is probably the

result of an insertion. (Note that this is much more

likely than the alternative possibility—that each of

the other species experienced an identical deletion

event in its past.) The type of pattern observed in

species Y often results from a SINE or LINE

insertion.

2. Copy the DNA sequences in Figure 7into your
   notebook. Align the homologous sections vertically.


3. Use a highlighter to colour all positions that have the
   same nucleotide in all four species.


4. Use a different colour to highlight the SINE
   insertion.

Analysis and Evaluation I

(a) Identify any nucleotide differences in the SINE

sequences. Explain how these differences might have

occurred.

(b) Identify whether mutations that occur within the

SINE are likely to be harmful, beneficial, or neutral.

Explain.

(c) Based on the data alone, construct a chart similar to

Table 1showing the phylogenetic relationship of

these species.

Part II: Evolution Displayed by SINEs and LINEs

Procedure II

5. Study the data in Table 1. DNA sequencing was used
   to document the presence or absence of interspersed
   elements A through I in five mammals. Camels are
   included as the outgroup.
   6. Use the data to construct a chart showing the
   phylogenetic relationships between these mammals.
   Clearly indicate the relative positions at which each
   insertion most likely occurred.

Analysis and Evaluation II

(d) Are whales more closely related to cows or

hippopotamuses? Explain your rationale.

(e) Identify which insertion happened first: A or B?

Explain your reasoning.

Synthesis

(f ) Explain whether pigs and camels are more closely

related than hippopotamuses and camels.

(g) What must be true about the genomes of all whale

species (i.e., which SINEs must they all contain)?

Explain your rationale.

(h) A researcher interested in the evolution of whales

wants to know whether orcas are more closely related

to white-sided dolphins or to pilot whales. Describe a

way to answer this question.

LAB EXERCISE 20.Bcontinued Table 1 Molecular Evidence for the Evolution of Whales*

Group SINE or LINE

AB CD E F GH I

cow  

pig  

whale  

deer  

hippopotamus  

camel  

+ indicates presence of element - indicates absence of element

* Data modified from Nikaido 1999

P AAAT TGC T T CGTATTTTCGAA

Q AACTTGCTTCGTAT TAAGC TG

S AACT TGCTACGTAT TAAGCCG

R

Species
Species

Species

Species AATTTGCTTCGTTTTTTCGAA

T TGCCCCGC TAAAGCGC T T TAGC

T TGCGTAAAGT TAGTACGAAT TGC

T TGCGTAAAGT TAGGACGAAT CGC

T TGCCCCGC TAAAGCGC T T TAGC

CCCGG T GAAGCGCTTTAGC

CACGG T GACGCGCT TGAGC

Figure 7

Homologous DNA sequences from four species