277
edits
Down syndrome: Difference between revisions
From CreationWiki, the encyclopedia of creation science
Jump to navigationJump to search
→Trisomy 21
(→:)) |
|||
| Line 15: | Line 15: | ||
==Trisomy 21== | ==Trisomy 21== | ||
[[Image:Trisomy_in_Down_syndrome.jpg|frame|right|[[Trisomy]], the hallmark of Down syndrome, results when a baby is born with three copies of [[chromosome]] 21 instead of the usual two.]] | |||
Down syndrome is a disease caused by an irregular number of chromosomes. There are three main causes of trisomy 21. [http://www.ds-health.com/trisomy.htm]The most common is called nondisjunction. Nondisjunction happens during cell division. When a cell goes normally through meiosis, the chromosome are divided evenly between the two daughter cells, but when no disjunction occurs, the chromosomes are split unevenly, giving one daughter cell extra chromosomes and the other one a less than normal amount. [http://www.wrongdiagnosis.com/n/nondisjunction/intro.htm] If and egg or sperm cell with and uneven number of chromosomes combines with a normal cell, the resulting fetus will have a third twenty-first chromosome, and therefore, will have Down syndrome. | Down syndrome is a disease caused by an irregular number of chromosomes. There are three main causes of trisomy 21. [http://www.ds-health.com/trisomy.htm]The most common is called nondisjunction. Nondisjunction happens during cell division. When a cell goes normally through meiosis, the chromosome are divided evenly between the two daughter cells, but when no disjunction occurs, the chromosomes are split unevenly, giving one daughter cell extra chromosomes and the other one a less than normal amount. [http://www.wrongdiagnosis.com/n/nondisjunction/intro.htm] If and egg or sperm cell with and uneven number of chromosomes combines with a normal cell, the resulting fetus will have a third twenty-first chromosome, and therefore, will have Down syndrome. | ||
| Line 21: | Line 23: | ||
The third cause of trisomy 21 is mosaicism. Mosaicism is a condition were an individual has cells that do not all have the same genes. Some cells have a normal number of chromosomes while others have an abnormal amount. This condition can affect a person’s sperm and egg cells as well. If a parents reproductive cells has and abnormal amount of chromosomes, their child could be born with Down syndrome.[http://www.nlm.nih.gov/medlineplus/ency/article/001317.htm] | The third cause of trisomy 21 is mosaicism. Mosaicism is a condition were an individual has cells that do not all have the same genes. Some cells have a normal number of chromosomes while others have an abnormal amount. This condition can affect a person’s sperm and egg cells as well. If a parents reproductive cells has and abnormal amount of chromosomes, their child could be born with Down syndrome.[http://www.nlm.nih.gov/medlineplus/ency/article/001317.htm] | ||
==Common Characteristics== | ==Common Characteristics== | ||
