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Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Sanders 3rd EditionCh. 17 - Organelle Inheritance and the Evolution of Organelle Genomes문제 6
17장, 문제 6

What are the differences between the universal code and that found in the mitochondria of some species? Given that some changes (UGA =stop→Trp) have occurred multiple independent times in evolution, can you think of any selective advantage to the mitochondrial code?

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Understand the universal genetic code: The universal genetic code is a set of rules by which the nucleotide sequence of mRNA is translated into the amino acid sequence of proteins. It is nearly universal across all organisms, with codons (triplets of nucleotides) specifying particular amino acids or signaling stop codons.
Identify differences in the mitochondrial genetic code: Mitochondria have their own DNA and use a slightly different genetic code. For example, in human mitochondria, the codon UGA, which is a stop codon in the universal code, is translated as tryptophan (Trp). Similarly, other codons like AUA (isoleucine in the universal code) are translated as methionine (Met) in mitochondria.
Consider the evolutionary context: Changes in the mitochondrial genetic code, such as UGA = stop → Trp, have occurred independently in different lineages. This suggests that these changes may have been driven by selective pressures specific to mitochondrial function or environment.
Evaluate potential selective advantages: One possible advantage of the mitochondrial code changes could be optimization for mitochondrial protein synthesis. For example, reassigning a stop codon to an amino acid like tryptophan might allow for more efficient or specialized protein production in the mitochondria, which is critical for energy production and cellular metabolism.
Reflect on mitochondrial specialization: Mitochondria are highly specialized organelles with unique requirements for protein synthesis. The deviations in their genetic code may reflect adaptations to their specific roles in energy production, oxidative stress management, and other cellular processes, providing a selective advantage in certain evolutionary contexts.

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Universal Genetic Code

The universal genetic code refers to the set of rules by which information encoded in genetic material (DNA or RNA) is translated into proteins. It consists of 64 codons, which correspond to 20 amino acids and serve as the foundation for protein synthesis across most organisms. This code is largely conserved, meaning that it is similar across diverse species, highlighting a common evolutionary origin.
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11:43
The Genetic Code

Mitochondrial Genetic Code

The mitochondrial genetic code is a variation of the universal genetic code found in the mitochondria of eukaryotic cells. It differs in several codon assignments, such as UGA, which typically signals a stop codon in the universal code but can code for tryptophan in some mitochondrial codes. These variations can arise due to evolutionary adaptations specific to the energy-producing functions of mitochondria.
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가이드 코스
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The Genetic Code

Selective Advantage

Selective advantage refers to a genetic trait that enhances an organism's ability to survive and reproduce in a specific environment. In the context of mitochondrial code variations, such as the reassignment of UGA, these changes may provide metabolic efficiencies or adaptations that improve energy production or stress responses, thereby offering a competitive edge in certain ecological niches.
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Natural Selection
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교과서 질문

Consider the phylogenetic tree presented in the following figure (Figure 17.17). How were the origins of secondary endosymbiosis in the brown algae determined?

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교과서 질문

Outline the steps required for a gene originally present in the endosymbiont genome to be transferred to the nuclear genome and be expressed, and for its product to be targeted back to the organelle of origin.

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교과서 질문

Draw a graph depicting the relative amounts of nuclear DNA present in the different stages of the cell cycle (G₁,S,G₂,M). On the same graph, plot the amount of mitochondrial DNA present at each stage of the cell cycle.

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교과서 질문

What is the evidence that transfer of DNA from the organelles to the nucleus continues to occur?

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교과서 질문

What is the evidence that the ancient mitochondrial and chloroplast endosymbionts are related to the alphaproteobacteria and cyanobacteria, respectively?

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교과서 질문

The human mitochondrial genome encodes only 22 tRNAs, but at least 32 tRNAs are needed for cytoplasmic translation. How are all codons in mitochondrial transcripts accommodated by only 22 tRNAs? The Plasmodium mitochondrial genome does not encode any tRNAs; how are genes of the Plasmodium mitochondrial genome translated?

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