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The double-helix structure of DNA was identified in 1953 by James Watson and Francis Crick. DNA strands are composed of long chains of molecules known as nucleotides.
Each nucleotide consists of three chemical components: a phosphate group, a five-carbon sugar, and one of the nitrogenous bases—adenine, guanine, cytosine, thymine, or uracil.
A gene is the fundamental unit of heredity. It is a specific sequence of nucleotides that carries the information required to produce functional biological molecules and, more broadly, to support the processes of life.
Genes contained in chromosomes
Genes are organized into chromosomes, which are located within the cell nucleus. Each chromosome contains hundreds or even thousands of genes.
Human cells typically contain 23 pairs of chromosomes, for a total of 46. Of these, 22 pairs are autosomes, while the remaining pair consists of the sex chromosomes. Females have two X chromosomes, whereas males have one X and one Y chromosome.
From the early 2000s onward, researchers developed a range of synthetic nucleic acid analogues collectively known as XNAs, or xeno nucleic acids.
Like DNA and RNA, XNAs are polymers capable of storing and transmitting genetic information. However, they differ from natural nucleic acids in the chemical structure of their backbone. The letter “X” stands for xeno, meaning foreign or alien, and highlights their molecular distinction from naturally occurring DNA and RNA.
Synthetic biologists investigate XNAs in order to design biological systems and molecular functions that do not exist in nature. Different forms of XNA are produced by replacing the natural sugar component of DNA or RNA with alternative molecules. Examples include threose nucleic acid, or TNA; glycol nucleic acid, or GNA; and hexitol nucleic acid, or HNA.
These structural modifications make it possible to create synthetic genetic systems with distinctive chemical properties, potentially enabling the development of artificial genes, new forms of molecular information storage, and biological mechanisms beyond those found in natural organisms.
XNA : Glycol
XNA : Glycol
XNA : Threose
XNA : Threose
XNA : Hexose
XNA : Hexose
XNA encompasses a variety of synthetic nucleic acid structures that differ chemically from their natural counterparts. These structures can incorporate alternative sugar backbones, such as threose, glycol, or hexitol, enabling the creation of xeno-nucleic acids and artificial genetic systems with properties distinct from those of natural DNA.
Xeno Dna with tetrahedral or octahedral helix structure
Unlike natural DNA, XNAs contain chemically modified molecular backbones and may therefore adopt a range of helical geometries and structural configurations. These differences can provide distinctive properties, including enhanced chemical stability, resistance to enzymatic degradation, and the ability to store and transmit sequence-defined genetic information.
Experimental studies have demonstrated that certain XNAs can undergo heredity and Darwinian evolution under controlled laboratory conditions. This makes them promising candidates for the development of synthetic genes, artificial chromosomes, and genetic systems that operate independently of natural DNA and RNA.
In the future, such technologies could contribute to the creation of highly engineered microorganisms or xeno-organisms with biological functions not found in nature. However, fully autonomous organisms whose genetic systems are based entirely on XNA have not yet been created, and their development remains a long-term objective of synthetic biology.
Meiosis
Meiosis
Mitosis
Mitosis
Embryonic
Embryonic
Meiosis is a specialized form of cell division in which a single cell undergoes two successive divisions, producing four daughter cells, each containing half the original number of chromosomes.
Mitosis, by contrast, is the process through which one cell divides to produce two genetically identical daughter cells, while preserving the same number of chromosomes as the parent cell.
Through the controlled duplication and distribution of synthetic chromosomes, researchers could theoretically initiate the development of an embryonic xeno-life form. However, the creation of a viable organism based entirely on an artificial genetic system remains a speculative objective rather than an established scientific achievement.
Syntetic virus created from Xna genes
Synthetic bacterium created from Xna genes
Synthetic chromosomes with Xna genes
Synthetic embryo models can progress beyond gastrulation, reaching neurulation and the early stages of organogenesis.
These integrated embryoid systems provide a powerful in vitro platform for investigating the roles of specific cell lineages, genes, and molecular pathways during development. The findings demonstrate that embryonic stem cells, together with two distinct types of extra-embryonic stem cells, can self-organize and partially reconstruct key stages of mammalian development, from gastrulation through neurulation and into early organ formation.
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