Concept explainers
To review:
The relationship between the number of synonymous substitutions and the years of divergence between each pair of species, with the help of a graph. Also, estimate the rates of synonymous substitutions per million years and per generation for the complete axon on a per-site basis.
Given:
In the given study, a hypothetical gene encodes for the transcription factor in various species of Drosophila. According to the diagram (Figure 1) given below, one exon of this gene is sequenced in four species.
Figure 1: Million of years ago.
The matrix shows the number of synonymous and nonsynonymous substitutions between pairs of different Drosophila species, which evolved as a result of evolution. There are 2,000 nonsynonymous and 600 synonymous substitutions sites of the exon (Figure 2).
Figure 2: Matrix showing the number of synonymous and nonsynonymous substitutions between pairs of species of Drosophila.
Introduction:
Biologists are able to make inference about the type of natural selection, by the study based on molecular evolutionary patterns of genes. These inferences are important to know, about the gene functioning and how they evolve over the time, in response to the new function and conditions.
Explanation of Solution
According to the given analysis, there are, on an average, 54 synonymous substitutions occurs between the lineages. These lineages were diverged 18 million years ago. So, there are about 1.5 synonymous substitutions per million year for the entire exon.
Therefore, the information used for calculation of the rate is:
Time period: 18 million years ago
Substitution per million years: 1.5
Lineages: 2
Generation per year: 5
Synonymous sites: 600
Thus, for rate of substitution per generation is:
90,000,000 years
Similarly, the rate of substitution per site is:
(90,000,000 years
Graph given below shows number of substitution along with millions of years.
Therefore, it can be concluded that the rates are 3
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Chapter 23 Solutions
LIFE: THE SCIENCE OF BIOLOGY
- Suppose species 1, 2, and 3 are endemic to a group of islands (such as the Galápagos) and are all descended from species 4, an outgroup. We sequence a gene and find ten nucleotide sites that differ among the four species (among many other loci that do not vary). The nucleotide bases at these sites are Species 1: GCTGATGAGT Species 2: ATCAATGAGT Species 3: GTTGCAACGT Species 4: GTCAATGACA Estimate the phylogeny of these taxa by plotting the changes on each of the three possible trees and determine which tree requires the fewest evolutionary changes. (Please answer including what are 3 possible trees.? )arrow_forwardA researcher studying two species (species 1 and species 2) sequences a short stretch of eight codons from the same gene, gene B, in each and compares them. Species 1 and species 2 had a most recent common ancestor 50 million years ago. Species 1: ATC GGG CGG GAC TTA CTA TAT GCC Species 2: ATT GGG CGG GAC TTG CTA TAT GCC Given the differences between the sequences of the two species' genes shown here, what evolutionary force can you predict is most likely in operation on gene B?arrow_forwardWhat is maximum likelihood (ML) in phylogenetics? The probability of the model of sequence evolution given the tree, the sequences, and the branch lengths O The probability of the tree given the sequences, the model of sequence evolution, and the branch lengths O The probability of the branch lengths given the sequences, the tree, and the model of sequence evolution O The probability of the sequences given the tree, the model of sequence evolution, and the branch lengthsarrow_forward
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