Gene And Genetic Code PdfBy Ethan B. In and pdf 02.02.2021 at 13:48 7 min read
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Genes are composed of DNA and are linearly arranged on chromosomes.
- Origin of the Genetic Code
- The Biological Significance of the Genetic Code
- Genetic code
- Heritable expansion of the genetic code in mouse and zebrafish
Origin of the Genetic Code
Although cells and tissues of mouse can be transduced transiently to incorporate Uaas 5 , it remains unknown whether transgenic vertebrates with a heritable expanded genetic code system-wide can be generated, as it is unclear whether the biological complexity of vertebrates allows the introduction, maintenance and transmission of the newly introduced genetic material for code expansion.
Here we for the first time report the generation of transgenic mice and zebrafish with an expanded genetic code, providing valuable vertebrate model animals for biological and biomedical research. Laboratory mouse Mus musculus is a widely used mammalian model for developmental, physiological and pathological studies due to its high genetic homology with humans.
The resulting offspring were viable and indistinguishable from WT littermates, and in general these crossing produced normal litter sizes along with a Mendelian inheritance pattern. Generation and characterization of transgenic mice and zebrafish with an expanded genetic code. A Schematic diagram of the construct used to generate transgenic mice and the reporter construct.
GAPDH serves as an internal loading control. The plot shows whole-transcriptome fragments per kilobase of exon per million fragments mapped FPKM. Representative images are shown for primary neuronal cells D , bone marrow cells E and fibroblasts F transduced with lentivirus carrying the reporter gene eGFP-amb-mCherry in the presence or absence of 1 mM AzF.
G Schematic diagram of the construct used to generate transgenic zebrafish and the reporter construct. The embryos were incubated in water with or without 2. The fluorescence images of whole embryos I , and mesenchymal J and notochord K tissues are shown. Arrowheads indicate cells with AzF incorporation. We next evaluated the potential impact of gene integration in the living mice.
F2 transgenic mice and descendants were used in subsequent characterization. Through histology analysis, no detectable morphological differences were observed between transgenic mice and the littermate controls from analyzed tissues including brain, heart, liver, colon, kidney, skeletal muscle and lung Supplementary information, Figure S1C.
To further assess effects of the transgene on gene expression, we used RNA-seq to analyze the transcriptomes of the liver tissue, where AzFRS showed the highest expression Figure 1B.
Among those liver-specific genes, the upregulated genes fell into a variety of categories related to metabolism Supplementary information, Figure S1D. Among the downregulated genes, there was a slight enrichment of primary metabolic enzymes associated with insulin signaling processes, suggesting that the transgene may have a repressive effect on primary metabolism in liver.
To test whether these small expression changes impaired the liver function in the transgenic line, we measured blood chemical indexes Supplementary information, Figure S1E.
No significant difference was observed between WT and transgenic mice in levels of blood aspartate transaminase AST , alanine transaminase ALT , albumin and other indexes.
Neurospheres isolated from the subventricular zone of transgenic mice were induced to differentiate into neurons and simultaneously transduced with the lentivirus carrying the eGFP-amb-mCherry reporter Figure 1D. In addition, through infecting with the eGFP-amb-mCherry reporter and adding AzF, amber suppression was also detected in primary bone marrow cells from transgenic mice Figure 1E but surprisingly absent in fibroblasts Figure 1F and Supplementary information, Figure S1G.
We also sought to expand the genetic code in zebrafish Danio rerio , which is a popular vertebrate model for live imaging and shares many conserved molecular and cellular mechanisms with mammals.
AzFRS expression was detected via its C-terminal FLAG tag in both larvae 2 days post fertilization dpf and adult caudal fin in F2 generation Figure 1H , revealing the successful and stable integration of the transgene. In the presence of AzF, there was a significant increase in the number of cells with eGFP signals 24 h post fertilization hpf , indicating suppression of the amber stop codon Figure 1I and Supplementary information, Figure S2B.
Images with higher magnification showed that the eGFP signal in the nucleus could be observed in all cell types analyzed, i. This work thus demonstrates the successful code expansion in living beings of a higher biological complexity than reported, suggesting unexpectedly high malleability of the genetic code. Of note, these vertebrate models can be equipped with Uaas of tailored chemical, physical and biological properties, e.
Uaa incorporation in vivo has the potential to impact developmental and behavior studies by precisely probing and manipulating target proteins in their native habitat.
Moreover, with Uaa-incorporated cells, tissues and whole animal derived from the same transgenic animal, it now becomes possible to correlate Uaa incorporation-enabled results from single cells to organs and the intact organism in a cohesive manner.
Science ; — Annu Rev Biochem ; 79 — ACS Chem Biol ; 7 — Nat Chem Biol ; 8 — Neuron ; 80 — Nature ; — Stem Cells ; 29 — Methods Mol Biol ; — Fehrentz T, Schonberger M. Trauner D. Angew Chem Int Ed Engl ; 50 — Nat Methods ; 10 — Chem Bio Chem ; 15 — Download references. Supplementary information is linked to the online version of the paper on the Cell Research website.
Supporting data figure for generation and characterization of transgenic mice with an expanded genetic code. PDF kb. PDF 71 kb. Reprints and Permissions. Chen, Y. Heritable expansion of the genetic code in mouse and zebrafish. Cell Res 27, — Download citation. Published : 09 December Issue Date : February Proceedings of the National Academy of Sciences Communications Biology Chem Frontiers in Bioengineering and Biotechnology ChemBioChem Advanced search. Skip to main content Thank you for visiting nature.
Download PDF. Subjects Biological models Genetic engineering Medical research. Figure 1. Full size image. View author publications. Additional information Supplementary information is linked to the online version of the paper on the Cell Research website. Supplementary information. Supplementary information, Figure S1 Supporting data figure for generation and characterization of transgenic mice with an expanded genetic code.
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The Biological Significance of the Genetic Code
Progress in Molecular and Subcellular Biology pp Cite as. The classical biologist, however, may find himself hard put to grasp the biological significance of this achievement. Would the cell we see today have been any different had not UUU been assigned to phenylalanine? Unable to display preview. Download preview PDF.
The genetic code is the set of rules used by living cells to translate information encoded within genetic material DNA or mRNA sequences of nucleotide triplets, or codons into proteins. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries. The code defines how codons specify which amino acid will be added next during protein synthesis. With some exceptions,  a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. The vast majority of genes are encoded with a single scheme see the RNA codon table. That scheme is often referred to as the canonical or standard genetic code, or simply the genetic code, though variant codes such as in human mitochondria exist.
Metrics details. Departures from the standard genetic code in eukaryotic nuclear genomes are known for only a handful of lineages and only a few genetic code variants seem to exist outside the ciliates, the most creative group in this regard. Most frequent code modifications entail reassignment of the UAG and UAA codons, with evidence for at least 13 independent cases of a coordinated change in the meaning of both codons. However, no change affecting each of the two codons separately has been documented, suggesting the existence of underlying evolutionary or mechanistic constraints.
Genetic code , the sequence of nucleotides in deoxyribonucleic acid DNA and ribonucleic acid RNA that determines the amino acid sequence of proteins. Though the linear sequence of nucleotides in DNA contains the information for protein sequences, proteins are not made directly from DNA. Three adjacent nucleotides constitute a unit known as the codon , which codes for an amino acid.
Translation is the process of translating the sequence of a messenger RNA mRNA molecule to a sequence of amino acids during protein synthesis. The genetic code describes the relationship between the sequence of base pairs in a gene and the corresponding amino acid sequence that it encodes. In the cell cytoplasm, the ribosome reads the sequence of the mRNA in groups of three bases to assemble the protein.
Халохот оглядел дворик. Он .
Heritable expansion of the genetic code in mouse and zebrafish
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Such genes are sometimes qualified by calling them structural genes or coding regions A synonym for gene is locus (plural = loci), the Latin word meaning site.
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