Why does the risk of down syndrome increases if the age of mother exceeds forty years?
Answers
Answered by
1
Down Syndrome
Definition
Down syndrome (DS) is the most common cause of mental retardation and malformation in a newborn. It occurs because of the presence of an extra chromosome. It was first described in 1866 by Dr. John L. H. Down (1828–1896), an English physician.
Down syndrome occurs about once in every 800 births. It is estimated that about 6,000 children are born with DS each year in the United States.
Veriato Computer Monitoring - Unmatched Visibility.
Veriato 360 Enterprise Computer Monitoring. Increase Productivity. Free Eval.
veriato.com/Monitoring/FreeEval | Sponsored▼
Description
Chromosomes are the units of genetic information that exist within every cell of the body. Twenty-three distinctive pairs, or 46 total chromosomes, are located within the nucleus (central structure) of each cell. When a baby is conceived by the combining of one sperm cell with one egg cell, the baby receives 23 chromosomes from each parent, for a total of 46 chromosomes. Sometimes, an accident in the production of a sperm or egg cell causes that cell to contain 24 chromosomes. This event is referred to as nondisjunction. When this defective cell is involved in the conception of a baby, that baby will have a total of 47 chromosomes. The extra chromosome in Down syndrome is labeled number 21. For this reason, the existence of three such chromosomes is sometimes referred to as trisomy 21.
Report Advertisement
In a very rare number of Down syndrome cases (about 1-2%), the original egg and sperm cells are completely normal. The problem occurs sometime shortly after fertilization; during the phase where cells are dividing rapidly. One cell divides abnormally, creating a line of cells with an extra chromosome 21. This form of genetic disorder is called a mosaic. The individual with this type of Down syndrome has two types of cells: those with 46 chromosomes (the normal number), and those with 47 chromosomes (as occurs in Down syndrome). Some researchers have suggested that individuals with this type of mosaic form of Down syndrome have less severe signs and symptoms of the disorder.
Dell® Business Laptops - Standard Free Shipping
Shop The World's Most Secure, Reliable Business-Class Laptops w/ Intel Core.
dell.com/Official/Site | Sponsored▼
Another relatively rare genetic accident which can cause Down syndrome is called translocation. During cell division, the number 21 chromosome somehow breaks. A piece of the 21 chromosome then becomes attached to another chromosome. Each cell still has 46 chromosomes, but the extra piece of chromosome 21 results in the signs and symptoms of Down syndrome. Translocations occur in about 3-4% of cases of Down syndrome.
Down syndrome occurs in about one in every 800-1,000 births. It affects an equal number of boys and girls. Less than 25% of Down syndrome cases occur due to an extra chromosome in the sperm cell. The majority of cases of Down syndrome occur due to an extra chromosome 21 within the egg cell supplied by the mother (nondisjunction). As a woman's age (maternal age) increases, the risk of having a Down syndrome baby increases significantly. For example, at younger ages, the risk is about one in 4,000. By the time the woman is age 35, the risk increases to one in 400; by age 40 the risk increases to one in 110; and by age 45 the risk becomes one in 35. There is no increased risk of either mosaicism or translocation with increased maternal age.
Down syndrome sometimes occurs together with such other developmental disorders as Rett syndrome. Although such double diagnoses are very rare, it is important for parents to recognize that the presence of one chromosomal abnormality does not exclude the possibility that their child may have a second anomaly.
Causes and symptoms
Report Advertisement
While Down syndrome is a chromosomal disorder, a baby is usually identified at birth through observation of a set of common physical characteristics. Babies with Down syndrome tend to be overly quiet, less responsive, with weak, floppy muscles. Furthermore, a number of physical signs may be present. These include:
flat appearing facesmall headflat bridge of the nosesmaller than normal, low-set nosesmall mouth, which causes the tongue to stick out and to appear overly largeupward slanting eyesextra folds of skin located at the inside corner of each eye, near the nose (called epicanthal folds)rounded cheekssmall, misshapen earssmall, wide handsan unusual, deep crease across the center of the palm (called a simian crease)a malformed fifth fingera wide space between the big and the second toesunusual creases on the soles of the feetoverly-flexible joints (sometimes referred to as being double-jointed)shorter than normal height
Definition
Down syndrome (DS) is the most common cause of mental retardation and malformation in a newborn. It occurs because of the presence of an extra chromosome. It was first described in 1866 by Dr. John L. H. Down (1828–1896), an English physician.
Down syndrome occurs about once in every 800 births. It is estimated that about 6,000 children are born with DS each year in the United States.
Veriato Computer Monitoring - Unmatched Visibility.
Veriato 360 Enterprise Computer Monitoring. Increase Productivity. Free Eval.
veriato.com/Monitoring/FreeEval | Sponsored▼
Description
Chromosomes are the units of genetic information that exist within every cell of the body. Twenty-three distinctive pairs, or 46 total chromosomes, are located within the nucleus (central structure) of each cell. When a baby is conceived by the combining of one sperm cell with one egg cell, the baby receives 23 chromosomes from each parent, for a total of 46 chromosomes. Sometimes, an accident in the production of a sperm or egg cell causes that cell to contain 24 chromosomes. This event is referred to as nondisjunction. When this defective cell is involved in the conception of a baby, that baby will have a total of 47 chromosomes. The extra chromosome in Down syndrome is labeled number 21. For this reason, the existence of three such chromosomes is sometimes referred to as trisomy 21.
Report Advertisement
In a very rare number of Down syndrome cases (about 1-2%), the original egg and sperm cells are completely normal. The problem occurs sometime shortly after fertilization; during the phase where cells are dividing rapidly. One cell divides abnormally, creating a line of cells with an extra chromosome 21. This form of genetic disorder is called a mosaic. The individual with this type of Down syndrome has two types of cells: those with 46 chromosomes (the normal number), and those with 47 chromosomes (as occurs in Down syndrome). Some researchers have suggested that individuals with this type of mosaic form of Down syndrome have less severe signs and symptoms of the disorder.
Dell® Business Laptops - Standard Free Shipping
Shop The World's Most Secure, Reliable Business-Class Laptops w/ Intel Core.
dell.com/Official/Site | Sponsored▼
Another relatively rare genetic accident which can cause Down syndrome is called translocation. During cell division, the number 21 chromosome somehow breaks. A piece of the 21 chromosome then becomes attached to another chromosome. Each cell still has 46 chromosomes, but the extra piece of chromosome 21 results in the signs and symptoms of Down syndrome. Translocations occur in about 3-4% of cases of Down syndrome.
Down syndrome occurs in about one in every 800-1,000 births. It affects an equal number of boys and girls. Less than 25% of Down syndrome cases occur due to an extra chromosome in the sperm cell. The majority of cases of Down syndrome occur due to an extra chromosome 21 within the egg cell supplied by the mother (nondisjunction). As a woman's age (maternal age) increases, the risk of having a Down syndrome baby increases significantly. For example, at younger ages, the risk is about one in 4,000. By the time the woman is age 35, the risk increases to one in 400; by age 40 the risk increases to one in 110; and by age 45 the risk becomes one in 35. There is no increased risk of either mosaicism or translocation with increased maternal age.
Down syndrome sometimes occurs together with such other developmental disorders as Rett syndrome. Although such double diagnoses are very rare, it is important for parents to recognize that the presence of one chromosomal abnormality does not exclude the possibility that their child may have a second anomaly.
Causes and symptoms
Report Advertisement
While Down syndrome is a chromosomal disorder, a baby is usually identified at birth through observation of a set of common physical characteristics. Babies with Down syndrome tend to be overly quiet, less responsive, with weak, floppy muscles. Furthermore, a number of physical signs may be present. These include:
flat appearing facesmall headflat bridge of the nosesmaller than normal, low-set nosesmall mouth, which causes the tongue to stick out and to appear overly largeupward slanting eyesextra folds of skin located at the inside corner of each eye, near the nose (called epicanthal folds)rounded cheekssmall, misshapen earssmall, wide handsan unusual, deep crease across the center of the palm (called a simian crease)a malformed fifth fingera wide space between the big and the second toesunusual creases on the soles of the feetoverly-flexible joints (sometimes referred to as being double-jointed)shorter than normal height
Meghanath777:
Is this the brainliest to you?
Similar questions