Biology, asked by Vishal101100, 2 months ago

Hello guys!


If a women over 40 year have a baby, it is always have a risk to the baby to have down syndrome ! why it is so ? Explain !​

Answers

Answered by Arpita102028
3

Answer

Women over age 35 are at higher risk for giving birth to a child with Down syndrome.

People have long recognized there is a connection between maternal age and Down syndrome.

In the early 1900s, researchers noticed children with the condition were frequently the last-born in large families and came shortly before a woman experienced menopause. At the time, they believed the condition was a sign that the mother had simply exhausted her reproductive potential.

Decades later, a French pediatrician made the association between the condition and an extra chromosome that was present in skin cells of some of his patients. We now understand even more about Down syndrome, including another cause that may run in families and is not associated with a woman’s age at the time she conceives.

But what’s really groundbreaking is we are starting to understand why maternal age matters for the development of Down syndrome.

More women are waiting to have children

On average, women in the United States are waiting later and later to have their first child. A recent report from the Centers for Disease Control and Prevention found that in 2014, the mean age of women having their first baby rose from 24.9 years to 26.3 years.

The report also found 9.1 percent of the first births happened in women over age 35, which is typically when we talk about an increased risk of chromosome abnormalities. Twenty percent of first births were in women age 30 to 34. For those women, subsequent additions to their families are accompanied with increasingly higher risks of chromosome abnormalities.

Causes of Down syndrome

There are actually three different causes of Down syndrome.

The most common is trisomy 21, which accounts for about 95 percent of all cases. “Tri” designates three – so instead of having two copies of chromosome 21 in each cell in the body, there are three. This typically happens when there is uneven division of the chromosomal material in the mother’s eggs – more on that later.

Another cause of Down syndrome, accounting for about 4 percent of cases, is translocation. This means that either a full or partial copy of chromosome 21 attaches to another chromosome. The presence of that extra material, even if it’s not a full chromosome, is enough to cause the characteristics of Down syndrome.

Answered by Anonymous
7

The most common is trisomy 21, which accounts for about 95 percent of all cases. “Tri” designates three – so instead of having two copies of chromosome 21 in each cell in the body, there are three. This typically happens when there is uneven division of the chromosomal material in the mother’s eggs – more on that later.

Another cause of Down syndrome, accounting for about 4 percent of cases, is translocation. This means that either a full or partial copy of chromosome 21 attaches to another chromosome. The presence of that extra material, even if it’s not a full chromosome, is enough to cause the characteristics of Down syndrome.

And finally, a very small percentage of cases are due to the child having a mixture of normal cells that contain two copies of chromosome 21 as well as some cells that contain three copies of the chromosome.

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