Question

what is a gene? state its functions

Answer 1

A gene is a locus (or region) of DNA which is made up of nucleotides and is the molecular unit of heredity.
Functions
1> helps in the inheritance of characteristics for one generation to another.

Answer 2

A gene is a locus (or region) of DNA which is made up of nucleotides and is the molecular unit ofheredity. The transmission of genes to an organism's offspring is the basis of the inheritance ofphenotypic traits. Most biological traits are under the influence of polygenes (many different genes) as well as thegene–environment interactions. Some genetic traits are instantly visible, such as eye colour or number of limbs, and some are not, such as blood type, risk for specific diseases, or the thousands of basic biochemical processes that comprise life.

Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotype traits. Colloquial usage of the term "having a gene" (e.g., "good genes," "hair colour gene") typically refers to having a different allele of the gene. Genes evolve due to natural selection or survival of the fittest of the alleles.

The concept of a gene continues to be refined as new phenomena are discovered.[3] For example, regulatory regions of a gene can be far removed from its coding regions, and coding regions can be split into several exons. Some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. Therefore, a broad, modern working definition of a gene is any discrete locus of heritable, genomic sequence which affect an organism's traits by being expressed as a functional product or by regulation of gene expression.[4][5]

Structure and function[edit]

  The structure of a eukaryotic protein-coding gene. Regulatory sequence controls when and where expression occurs for the protein coding region (red). Promoter and enhancer regions (yellow) regulate the transcription of the gene into a pre-mRNA which is modified to add a 5' cap and poly-A tail (grey) and remove introns. The mRNA 5' and 3' untranslated regions (blue) regulate translation into the final protein product.   The structure of a prokaryotic operon of protein-coding genes. Regulatory sequence controls when expression occurs for the multiple protein coding regions (red). Promoter, operator and enhancer regions (yellow) regulate the transcription of the gene into an mRNA. The mRNA untranslated regions (blue) regulatetranslation into the final protein products.

The structure of a gene consists of many elements of which the actualprotein coding sequence is often only a small part. These include DNA regions that are not transcribed as well as untranslated regions of the RNA.

Firstly, flanking the open reading frame, all genes contain a regulatory sequence that is required for their expression. In order to be expressed, genes require a promoter sequence. The promoter is recognized and bound by transcription factors and RNA polymerase to initiate transcription.[2]:7.1 A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end.[30] Promoter regions have a consensus sequence, however highly transcribed genes have "strong" promoter sequences that bind the transcription machinery well, whereas others have "weak" promoters that bind poorly and initiate transcription less frequently.[2]:7.2 Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.[2]:7.3

Additionally, genes can have regulatory regions many kilobases upstream or downstream of the open reading frame. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site.[31] For example, enhancers increase transcription by binding anactivator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.[32]

The transcribed pre-mRNA contains untranslated regions at both ends which contain a ribosome binding site, terminator and start and stop codons.[33] In addition, most eukaryotic open reading frames contain untranslated intronswhich are removed before the exons are translated. The sequences at the ends of the introns, dictate the splice sites to generate the final mature mRNA which encodes the protein or RNA product.[34]

Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit.[35][36] The products of operon genes typically have related functions and are involved in the sameregulatory network