21) Phylogenetic trees construicted from evidence from molecular systematics are
ID: 268785 • Letter: 2
Question
21) Phylogenetic trees construicted from evidence from molecular systematics are based on similarities in A) biochemical pathways B) C) habitat and lifestyle choices D) the pattern of embryological development E) mutations to homologous genes The question(s) below refer to the following table, which compares the % sequence homology of four different parts (two introns and two exons) of a gene that is found in five different eukaryotic species. Each part is numbered to indicate its distance from the promoter (for example, Intron I is the one closest to the promoter). The species A were obtained by comparing DNA from one member of species A to another member of species A. Exon I Intron VI Exon V 100% 100% 100% 100% 97% 94% 99% 80% 22) Based on the tabular data, and assuming that time advances vertically, which phylogenetic tree is the most likely depiction of the evolutionary relationships among these five species? B) A) O B A CE E C BD A D) C) of these four gene parts should allow the construction of the most accurate phylogenetic tree, 23) Whicho that this is the only part of the gene that has acted as a reliable molecular clock B) Exon V A) Intron VI C) Exon I D) Intron IExplanation / Answer
21) We know that features of a specific living being will give information about its origins and similarities in comparison to other living beigns; however, this is not a reliable way to set how silimar is a living being to another one, even though Darwin began to compare living beaings this way.
As we know, habitat and lifestyle choices are decisions that we take and even though this is influenced by genetics and environment, that's not the right answer. Biochemical pathways, morphology and pattern of embryological development are features but they are set by genetics. We need a reliable characterstic less influence by environment and only influenced by origin. We know that every single living being has a genetic code and this is inherited from its parents. This a characteristic that changes from generation to generation . So, we need genetics to know how similar is a living being to another one. We analyze mutations to homologous genes (homologous means the same gene but in another living being) because its a reliable way to know it and this is the way evolution is analyzed.
That's why the answer is letter E.
22)Phytogenetic trees show how similar is a specie to another one and we can observe that because the distance between them is longer.
% of homology is how similar is a gene, intron or exon to another one from another specie. As the % decreases, less similar are these species between each other. We have to take into account that specie A has 100% of homology in every intron and exon because specie A is the base. Since the specie E has the lowest values of % of homology, we can say that this specie is the less similar to specie A.
If we keep on analyzing, we will see that the order from the less similar to the most similar to specie A will be: E-B-C-D-A. That's why the right answer is letter D.
23) We need a genetic sequence, whose % of homology is different from a specie to another one. This would be a reliable molecular clock because we could see differences between species. In this case intron VI is the most different between species. That's why the answer is letter A.
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