Content deleted Content added
fixing typos |
Rescuing 2 sources and tagging 0 as dead.) #IABot (v2.0 |
||
Line 41:
[[File:DNA replication split.svg|thumb|left|[[DNA replication]]. DNA is unwound and [[nucleotide]]s are matched to make two new strands.]]
If the sequence of the nucleotides in a gene changes, the sequence of the amino acids in the protein it produces may also change—if part of a gene is deleted, the protein produced is shorter and may not work anymore.<ref name=NIGMS/> This is the reason why different alleles of a gene can have different effects on an organism. As an example, hair color depends on how much of a dark substance called [[melanin]] is put into the hair as it grows. If a person has a normal set of the genes involved in making melanin, they make all the proteins needed and they grow dark hair. However, if the alleles for a particular protein have different sequences and produce proteins that can't do their jobs, no melanin is produced and the person has white skin and hair ([[albinism]]).<ref>[http://www.albinism.org/publications/what_is_albinism.html What is Albinism?] {{Webarchive|url=https://web.archive.org/web/20120514003907/http://albinism.org/publications/what_is_albinism.html |date=14 May 2012 }} The National Organization for Albinism and Hypopigmentation, Accessed 20 May 2008</ref>
===Genes are copied===
Line 68:
==Genetic engineering==
{{main|Genetic engineering}}
Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how [[genetic engineering]] works. For example, rice can be given genes from a maize and a soil bacteria so the rice produces [[beta-carotene]], which the body converts to Vitamin A.<ref>Staff [http://www.goldenrice.org/ Golden Rice Project] Retrieved 5 November 2012</ref> This can help children suffering from Vitamin A deficiency. Another gene being put into some crops comes from the bacterium ''[[Bacillus thuringiensis]]''; the gene makes a protein that is an [[insecticide]]. The insecticide kills insects that eat the plants but is harmless to people.<ref>[http://ars.usda.gov/is/ar/archive/nov99/pest1199.htm Tifton, Georgia: A Peanut Pest Showdown] USDA, accessed 16 May 2008</ref> In these plants, the new genes are put into the plant before it is grown, so the genes are in every part of the plant, including its seeds.<ref>[http://www.gmo-safety.eu/basic-info/129.bacterial-arsenal-combat-chewing-insects.html Genetic engineering: Bacterial arsenal to combat chewing insects] {{Webarchive|url=https://web.archive.org/web/20110515134013/http://www.gmo-safety.eu/basic-info/129.bacterial-arsenal-combat-chewing-insects.html |date=15 May 2011 }} GMO Safety, Jul 2010</ref> The plant's offspring inherit the new genes, which has led to concern about the spread of new traits into wild plants.<ref>[http://www.geo-pie.cornell.edu/gmo.html Genetically engineered organisms public issues education] Cornell University, Accessed 16 May 2008</ref>
The kind of technology used in genetic engineering is also being developed to treat people with [[genetic disorder]]s in an experimental medical technique called [[gene therapy]].<ref>{{cite web| last = Staff|date= November 18, 2005| url = http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml| title = Gene Therapy| format = FAQ| work = Human Genome Project Information| publisher = [[Oak Ridge National Laboratory]]| accessdate = 2006-05-28}}</ref> However, here the new gene is put in after the person has grown up and become ill, so any new gene is not inherited by their children. Gene therapy works by trying to replace the allele that causes the disease with an allele that works properly.
| |||