Although our genome includes approximately 25,000 protein encoding genes, our cells can produce some 400000 different proteins.
How can so few genes specify so many proteins
- INTRONS: by removing different combinations of introns from mRNA molecule, a cell can produce several proteins from one gene
What is the function of the 98.5 % of our genome that does not encode protein
- some are regulatory ( e.g. Enhancers that control gene expression
- much is transcribed to rRNA, tRNA, & microRNA
- chromosomes also contain pseudogenes that are not able to be translated
- TRANSPOSON: The human geneome is riddled with highly repetitive squences that have no known function. The most abundant type are TRANSPOSON ( these moveable pieces of Dna make up 45% of the human geneome
- TANDEM REPEATS: ( AKA SATELITE DNA)
found in silent Dna, consist of one or more bases repeated several times
DNA sequences that are very similarto protein encoding genes and that are transcribed but whose mRNA is not translated into protein
How can the number of proteins encoded in DNA exceed the number of genes in the genome?
The 25,000 or so genes can make 400,000 proteins in part by changing which introns are removed prior to splicing together the mRNA.
List some functions of the 98.5% of the human genome that does not specify protein
Some of the 98.5% of the human genome that does not code for protein encodes rRNA, tRNA, and regulatory sequences that control gene expression. It also contains pseudogenes that may be remnants of non-functional DNA that encoded proteins in our ancestors; transposons (transposable elements) that jumped from bacteria and viruses to humans; and tandem repeats of DNA sequences in telomeres, centromeres, and on the Y chromosome.