A nuclear gene is a gene located in the cell nucleus of a eukaryote. The term is used to distinguish nuclear genes from the genes of the endosymbioticorganelle, that is genes in the mitochondrion, and in case of plants and algae, the chloroplast, which host their own genetic system and can produce proteinsfrom scratch. Eukaryotic genomes have distinct higher-order chromatin structures that are closely packaged and ultimately organized in a certain construct that functionally relates to gene expression. These cells function to package the genome "several thousand-fold into the confines of the cell nucleus," ensuring the maintenance of the gene accessibility along with chromatin structure, which accommodate highly dynamic processes such as: gene transcription, replication, and DNA repair. It is important to understand the mechanisms and molecular contributors involved in genome organization, this is essential in order to fully comprehend the fundamental relationship between nuclear organization and genome function. Nuclear genes also play major roles in the expression of chloroplast genes. Vast amounts of nuclear genes are required for mRNA processing. The majority of proteins in a cell are the product of messenger RNAtranscribed from nuclear genes, including most of the proteins of the organelles, which are produced in the cytoplasm like all nuclear gene products and then transported to the organelle. Genes in the nucleus are arranged in a linear fashion upon chromosomes, which serve as the scaffold for replication and the regulation of gene expression. As such, they are usually under strict copy-number control, and replicate a single time per cell cycle. Many nuclear-derived transcription factors have played a role in respiratory chain expression. These factors may have also contributed to the regulation of mitochondrial functions. Nuclear respiratory factorfuses to respiratory encoding genes proteins, to the rate-limiting enzyme in biosynthesis, and to elements of replication and transcription of mtDNA.The second nuclear respiratory factor is necessary for the production of cytochrome c oxidase subunit IV and Vb to be maximized. Nuclear cells such as platelets do not possess nuclear DNA and therefore must have alternative sources for the RNA that they need to generate proteins.
