Concept explainers
Why might mitochondrial, Y chromosome, and autosomal DNA provide different perspectives on our evolutionary past
To analyze:
The reason for the relationship of mitochondria, Y chromosome, and autosomal DNA with different aspects of our evolutionary past, for example regarding our relationship with Neandertals.
Introduction:
The evolutionary relationships of closely related organisms show different evolutionary processes in a relatively short time that has been of interest to a biologist since a long time. The comparative study of phylogenies concluded from the DNA sequences with different inheritance patterns i.e. mitochondrial, autosomal, and X & Y chromosomal loci delivers best widespread conclusions of the evolutionary history.
Explanation of Solution
Mitochondria DNA: The first genetic evidence for an African origin of modern humans was analyzed from the study of mitochondrial DNA (mtDNA) polymorphism. The mtDNA specifically gives the genealogical history and evolutionary relationship of mammalian species.
The mtDNA are inherited maternally; they do not show any recombination of alleles; unlike the nuclear genome, some non-coding mtDNA can evolve quickly which leads to a variation in the mtDNA within closely related species. In mammals, the rate of mutation in mtDNA is higher than nuclear genomes i.e.
The regions around the Great Rift Valley of East Africa have been home to humans and hominin ancestors for at least 4 million years. The model of Human evolution called as RAO model (for recent African origin) proposes humans are evolved from a small African population. The RAO model suggests that modern humans arose approximately
Y chromosome: The Y chromosome sequence variation provides complementary mtDNA analysis. Y chromosome is strictly paternally inherited, and outside the pseudo-autosomal region, it does not show any recombination with other chromosomes. Y chromosome sequence is poor and provides very less sequence diversity. It has short tandem repeats (Y-STR) that can mutate rapidly about
According to the RAO model, more diversity is observed within African Y chromosome sequence than non-African sequences. As the mtDNA and Y chromosomes are strictly maternal and paternal, their haplotypes can be used to trace the migration patterns.
Autosomal DNA: The analysis of thousands of human genome sequences demonstrated that autosomal genetic diversity in African population is greater compared to the non-African population. Likewise, the study of Single nucleotide polymorphic DNA of worldwide sample population revealed the highest frequency of unique alleles in Africans compared to Non- Africans.
From all of these aspects, the mtDNA of Neandertals is different from the modern human, and it also does not show any inbreeding. The comparative nuclear genome sequences revealed that
The hybridization of Neandertals genome with modern human genome revealed that inbreeding took place after the migration of modern humans out of Africa. The other analysis also revealed that Neandertal DNA is unevenly distributed in the human genome; for example, no Neandertal DNA on the X chromosome, rather on autosomes, carries Neandertal DNA with precise distribution.
The comparative study of phylogenies concluded from the DNA sequences with different inheritance patterns i.e. mitochondrial, autosomal, and X & Y chromosomal loci, delivers best widespread conclusions of the evolutionary history.
Want to see more full solutions like this?
Chapter D Solutions
Study Guide And Solutions Manual For Genetic Analysis: An Integrated Approach
- Genomics and Human Evolution The Denisovan genome contains sequences that originated from an unknown human species. Using Figure 19.11, speculate on which species this might be. Is it possible that there are other ancestral species that may remain to be discovered that would change the phylogeny presented in the figure? FIGURE 19.11 Estimates for the dates of origin and extinction for the three main groups of hominins (green, blue, and orange). The australopithecines split into two groups about 2.7 million years ago. One of those groups, the genus Homo, contains the ancestors to our species, H. sapiens.arrow_forwardIf mutations such as those of the Ubx gene can drastically change morphology in a single step, why do most evolutionary biologists maintain that modification of existingtraits and the evolution of novel characters have generally proceeded by successive small steps?arrow_forwardWhy do you think such a small portion of Neandertal or Denisovan DNA exists in the gene pool of modern humans?Β Why not more?arrow_forward
- As pointed out in the section Evolution of the Y Chromosome, some researchers have predicted that the human Y chromosome will continue to lose genetic information in the future and will completely disappear from the species in about 10 million years. What would happen if the Y chromosome disappeared from the human species?arrow_forwardDenisovans are ancient humans. What would you least expect? Β A. They would have a larger brain than H. floresiensis. Β B. Fusion of chromosome 2a and 2b would not have occurred. Β C. Their mtDNA would show more similarity to Neanderthals than to H. sapiens. Β D. They probably did not have a spoken language. Β E. There would be evidence of them interbreeding with Homo sapiens and Neanderthals.arrow_forwardWhen I first studied hominin evolution, they had found "Lucy", an Australopithecus afarensis, and everyone thought her species was an early ancestor of Homo sapien. The picture is much more complicated, with lots of hominins living in close proximity for millions of years...much different than our now singular species. Look at the phylogenetic tree and use it as a guide to briefly describe hominin lines in Africa up to Homo. Do not discuss Homo.Just discuss a sense that you generally can grasp what was going on in Africa with our Genus for 6 or 7 million years!arrow_forward
- How would cladists and evolutionary taxonomists differ in their interpretations of the statement that humans evolved from apes, which evolved from monkeys?arrow_forward. As of this writing in 2016, no Neanderthal-derivedY chromosome nor mitochondrial DNA sequenceshas ever been found in a modern human. Proposetwo alternative explanations.arrow_forwardHow do modern evolutionists view the relationship between ontogeny and phylogeny? Explain how the observation of paedomorphosis conflicts with Haeckelβs βbiogenetic law.βarrow_forward
- If mutations such as those of the Ubx gene candrastically change morphology in a single step,why do most evolutionary biologists maintainthat modification of existing traits and the evolution of novel characters have generally proceeded by successive small steps?arrow_forwardHow do these similarities and differences relate to the evolutionary relationships between these species?arrow_forwardConsidering the evolution of species, could a gene that is conserved from yeast to humans have evolved to confer some of the complex traits that we observe in modern animals, like multicellularity? Briefly explain.arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning