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?

Verified step by step guidance

1. Understand that the human mitochondrial genome uses a reduced set of tRNAs due to a phenomenon called 'wobble pairing', where the third base of the codon can pair with more than one base in the anticodon of the tRNA, allowing fewer tRNAs to recognize multiple codons.
2. Recognize that the genetic code in mitochondria is slightly different from the universal genetic code, which allows for some codons to be read differently, further reducing the number of tRNAs needed.
3. For Plasmodium, note that its mitochondrial genome does not encode tRNAs, which suggests that it relies on importing tRNAs from the cytoplasm into the mitochondria for translation.
4. Consider the role of the mitochondrial import machinery, which facilitates the transport of necessary tRNAs from the cytoplasm into the mitochondria in organisms like Plasmodium.
5. Reflect on the evolutionary implications of these adaptations, such as the efficiency of the mitochondrial genome and the reliance on host cellular machinery for translation in Plasmodium.

Key Concepts

Mitochondrial tRNA and Codon Usage

Mitochondrial tRNAs are specialized molecules that facilitate the translation of mitochondrial mRNA into proteins. Despite the human mitochondrial genome encoding only 22 tRNAs, the genetic code allows for some tRNAs to recognize multiple codons due to wobble base pairing. This flexibility enables the accommodation of all mitochondrial codons, even with a limited number of tRNAs.

Wobble Hypothesis

The wobble hypothesis explains how the third position of a codon can pair with multiple tRNA anticodons, allowing a single tRNA to recognize more than one codon. This phenomenon is crucial in mitochondrial translation, where the reduced number of tRNAs must still cover the full range of codons. It highlights the efficiency of the genetic code and the adaptability of tRNA molecules.

Alternative Translation Mechanisms in Plasmodium

The Plasmodium genus, which includes malaria-causing parasites, has evolved unique mechanisms for translating its mitochondrial genes despite lacking tRNAs. These organisms utilize nuclear-encoded factors or rely on host cell machinery to facilitate translation. This adaptation underscores the diversity of genetic translation strategies across different organisms, particularly in parasitic species.