iSpace Web Page of cea: Class of 2010
Chromosomal Mutations
Different species of organisms each have a specific number of chromosomes. For example, humans have 23 pairs of chromosomes and therefore a total of 46 chromosomes. This is the normal number of chromosomes for the species, however there are situations in which individuals have aberrations, or disruptions in the normal chromosome content of a cell. Chromosomal mutations create changes in whole chromosomes (multiple genes) or in the number of chromosomes present. These aberrations can result in various serious disorders, such as Down Syndrome; the specific disorder depends on where there is an extra or missing chromosome. Situations in which a chromosome is missing or there is an extra chromosome can be lethal or lead to serious disorders. However, in other situations, such as inversions, carriers do not have the disease, but their children have a bigger chance of having a disorder. You can see all an individuals chromosome pairs in something called a karyotype, and can therefore see if there is a large error in any of an individual's chromosomes, such as an extra or deleted chromosome or part of a chromosome.
This is an image of a karyotype of healthy human male.
http://www.biotechnologyonline.gov.au/popups/img_karyotype.cfm
Types of Chromosomal Mutations:
Duplication- results in extra copies of a part of a chromosome or of a whole chromosome
http://content.answers.com/main/content/wp/en/thumb/4/4c/220px-Chromosome_duplication.jpg
Deletion- the loss of part or all of a chromosome.
http://content.answers.com/main/content/wp/en-commons/5/5f/Deletion.gif
Translocation- results when part of a chromosome breaks off and attaches to another chromosome.
http://content.answers.com/main/content/wp/en/thumb/5/50/180px-Translocation-4-20.png
Inversion- results when the position of a segment of the chromosome is changed so that the linear order of the genes is reversed on the chromosome
http://evolution.berkeley.edu/evosite/history/images/inversion.gif
Examples of Human Chromosomal Disorders:
- Cri du chat-This disorder is caused by the deletion of part of the short arm of chromosome 5. Cri du chat causes babies to have high-pitched cries that sound like a cat, hence the disorder's name. Affected individuals have wide-set eyes, a small head and jaw and have moderate to severe mental retardation and are very short.
- Down Syndrome-This disorder, the most common trisomy, is caused by an extra copy of chromosome 21 (trisomy 21). The characteristics include decreased muscle tone, asymmetrical skull, slanting eyes, and mild to moderate mental retardation.
- Edward's Syndrome-This disorder, a trisomy of chromosome 18, is the second most common trisomy after Down Syndrome. Symptoms include mental and motor retardation as well as multiple congenital anomalities that cause serious health problems. About 90% die in infancy, while those who live past a year are usually healty afterwords. Affected individuals have charecteristically clenched hands and overlapping fingers.
Why Did I Pick This Topic?
I choose to do my iSpace about chromosomal mutations because i was really interested in the whole genetics topic that we covered in biology class, and was curious to further research it. Then, I found chromosomal mutations to be a good subtopic of genetics to base my iSpace on. I was really interested on how the different types of mutations occur and how they can have such a huge variety of effects on organisms.