Difference between revisions of "Gene"
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Revision as of 01:47, 9 July 2014
A gene is defined as a functional unit of genetic inheritance that is located at a physical position on a chromosome and ultimately contributes to a phenotype.
Contents
Misconceptions
- Genes do not have to be organized into discrete units along a strand of DNA. Functionally different genes can overlap.
- Genes do not always code for a polypeptide (protein) sequence. Many genes code for RNA sequences with their own function distinct from protein coding mRNA.
- There is confusion between the definitions of genes and alleles. Alleles are versions of genes. There is not a gene for red hair or blue eyes in people. There are alleles of genes that can result in red hair or blue eyes (in the right genotype configuration).
Generalities
Genes have a promoter that initiates transcription of the DNA sequence by an RNA polymerase into an RNA sequence.
Common Example
Protein Coding Genes
Non-Coding RNA
Exceptions
- In the case of RNA virus genome, genes do not exist as DNA but are RNA sequences.
- It is difficult to precisely define the physical boundaries of a gene. Sequences that affect expression can sometimes be found at a long distance away or even on different chromosomes.
