Question

19. A couple's only child has Down Syndrome. An examination of the child's karyotype reveals that he has 46 chromosomes per cell, but that one chromosome is unusually large, and appears include large portions of chromosome 14 and chromosome 21. The couple fears that if they have another child, it will also have Down Syndrome. a. Estimate the probability that their next child would have Down Syndrome. Show your work. b. The mother is 25 and learned from her genetics course that for a woman her age, the chance of giving birth to a child with Down syndrome is 1 in 120S. Should the couple expect that their chances of having a Down syndrome child are about 1 in 1205? Explain. Note for b: you can assume that the observation of 1 in 1205 women having a Down- Syndrom e child is accurate. In other words, there was no significant sampling error.)

Answer 1

DOWN SYNDROME

It is a symptom appeared when there is the fault in one or more than one chromosomes, chromosomes are the design which holds genes and genes are the parts of cells of the body that provides instruction to the body hoe they have to function and work.

down syndrome is also called trisomy 21 and it the most common abnormality of chromosomes in the developed nations.

down syndrome occurs when there is an extra copy of 21st chromosomes developed, in every individual, there are 23 pairs of chromosomes, one from father and another from the mother but in down syndrome, the extra copy of 21 st chromosomes brings changes in mind and body functioning. the exact cause of having down syndrome is not known, some assumption is like the sperm that fertilizes the egg carries extra chromosomes, etc.

a) Answer

your age is one of the main factors when you get pregnant and chances of having a baby with down syndrome,

the more your age is the higher your chance is to develop down syndrome, some

if you already have a baby with down syndrome, the risk of having another baby with the same condition increases with each pregnancy up to the ag 40 years, the chances of having the baby with down syndrome is 1 in 100 with each successive pregnancy.

it is necessary to contact a genetic counselor to be aware of the genetic defect and other problems that rums in the family of father or mother.

Different types of down syndromes are :

1. Trisomy 21.

it is the common type of down syndrome and the chances of developing this kind of down syndrome are 96 out of 100 children with down syndrome, in this condition, there is an extra copy of 21 st chromosomes are seen which alters brain and body normal functioning.

2. A large portion of chromosomes 14 mosaics down syndrome.

This type of chromosomal defects occurs rarely and has fewer chances of developing down syndrome, the 14th chromosomes play an important role in bodybuilding and maintains and control various function of the body, some times 3 copies of chromosomes 14th causes defect that leads to down syndrome.

so, it is better to get the early screening and all the lab test done including regular ultrasound to avoid a chromosomal defect in the baby and also to produce eugenics baby in the community to live his / her life to the fullest.

b) Answer

age is the important factors of delivering a baby with down syndrome, the more the age of mother the higher the chances of delivering the baby with the down syndrome.

at age 25 the risk of having the baby with down syndrome is 1 in 1205

at age 30 risk of having a baby with Down syndrome is 1 in 940

at age35 risk of having a baby with Down syndrome is 1 in 353

at age 40 risk of having the baby with Down syndrome is 1 in 85

BUT REGARDLESS OF THE AGE ALL WOMEN WHO ARE PREGNANT SHOULD BE OFFERED GENETIC TESTING OR SCREENING, ALL BLOOD TEST AND ALSO THE THICK MASS THAT APPEARED ON THE BABY'S NECK WITH DOWN SYNDROME CAN BE DETECTED IN ULTRASOUND AND THE COMPLICATION CAN BE AVOIDED.

AND ALSO DNA TEST OF FETUS IN THE FIRST TRIMESTER OF PREGNANCY HELPS IN DETECTING DOWN SYNDROME WITH THE 90 % ACCURACY RATE.

IN the 2ND TRIMESTER MULTIPLE MARKER SCREENING HELPS IN DETECTION OF DOWN SYNDROME WITH 80 % OF ACCURACY.

IF ABOVE TEST WARNS YOU YOU CAB GO FOR AMNIOCENTESIS AND CHORIONIC VILLI SAMPLING TEST WITH VERY LITTLE CHANCES OF MISCARRIAGE, ALSO TAKE ALL THE ESSENTIAL NUTRIENTS DURING PREGNANCY TO VOID CHROMOSOMAL DEFECTS,

IF IS DETECTED AT THE EARLY PHASE OF PREGNANCY THERE ARE VARIOUS SERVICES BY THE GOVERNMENT WHO OFFERS SERVICES FOR THE MOTHER AND THE CHILD WITH DOWN SYNDROME, THERE ARE VARIOUS AGENCIES WHO WORK FOR THE CHILDREN WITH DOWN SYNDROME AND OTHER CHROMOSOMAL DEFECT TO LEAD A HAPPY AND MEANINGFUL LIFE IN THE WORLD.