The Occurrence of Down Syndrome Most of the time, the occurrence of Down syndrome is due to a random event that occurred during formation of the reproductive cells, the ovum or sperm. As far as we know, Down syndrome is not attributable to any behavioral activity of the parents or environmental factors. The probability that another child with Down syndrome will be born in a subsequent pregnancy is about 1 percent, regardless of maternal age. For parents of a child with Down syndrome due to translocation trisomy 21, there may be an increased likelihood of Down syndrome in future pregnancies. This is because one of the two parents may be a balanced carrier of the translocation. The translocation occurs when a piece of chromosome 21 becomes attached to another chromosome, often number 14, during cell division. If the resulting sperm or ovum receives a chromosome 14 (or another chromosome), with a piece of chromosome 21 attached and retains the chromosome 21 that lost a section due to translocation, then the reproductive cells contain the normal or balanced amount of chromosome 21. While there will be no Down syndrome associated characteristics exhibited, the individual who develops from this fertilized egg will be a carrier of Down syndrome. Genetic counseling can be sought to find the origin of the translocation. However, it is important to realize that not all parents of individuals with translocation trisomy 21 are themselves balanced carriers. In such situations, there is no increased risk for Down syndrome in future pregnancies. Researchers have extensively studied the defects in chromosome 21 that cause Down syndrome. In 88% of cases, the extra copy of chromosome 21 is derived from the mother. In 8% of the cases, the father provided the extra copy of chromosome 21. In the remaining 2% of the cases, Down syndrome is due to mitotic errors, an error in cell division which occurs after fertilization when the sperm and ovum are joined. The incidence of Down syndrome rises with increasing maternal age. From: Ali Sabah Al-Takmachi, College: Medicine , UOS Reference: http://www.nichd.nih.gov/publications/pubs/downsyndrome.cfm
A description, often mathematical, of how (not why) a process occurs.
Evaporation occurs when particles have enough energy to escape as gas from the suface of the liquid. So it occurs all the time, just that the rate at which it occurs is slowed down or speeded up by other factors such as humidity, surface are exposed, wind, temperature & light (sun).
They move up and down, but do not move forward (NJASK8 Earth Science)
There are instances when corrosion occurs at the junction of a carbon steel pipe and a brass valve. This is often the result of a pipe threading failure.
The theory of rapid evolution rather than over a very long time.
Down Syndrome often occurs when chromosomes fail to separate properly during meiosis.
Secondary succession occurs most often
it occurs often
lightning occurs quite often in florida. it occurs at least 5 times a month.
If you mean annual event, it occurs yearly.
The mode reports that value that occurs most often.
You really shouldn't be looking for the answer of a test or homework on the computer. But the answer is How often a wave occurs is the waves frequency.
earthquakes
Mesothelioma pictures are often targeted where the mesothelioma occurs. It typically occurs in the lungs since the fibers are often inhaled when they become airborn.
frequency
Yes, erosion occurs when something like a rock and a wave break it down over time.
When there is a presence of external negativity market failure often occurs because there is no trust left between a business and society. For example, a corporation that is openly protesting human rights, may have a fluctuation in stock prices that is so low as to cause a shut down of the business.