Step 1: Read the diagram:
The diagram shows fluid being withdrawn with a syringe from the amniotic cavity of a pregnant uterus. The fluid is centrifuged. Cells settle at the bottom and are cultured in a dish.
This is the procedure called amniocentesis.
Step 2: Part (a): explain the procedure:
A little amniotic fluid is drawn through the abdominal wall with a thin needle, usually at the 14th to 16th week of pregnancy.
The fluid holds cells shed by the foetus. After centrifugation these cells are cultured.
Their chromosomes and enzymes are then examined to find genetic and metabolic disorders.
Step 3: Part (a): one advantage and one disadvantage:
Advantage: it detects chromosomal disorders (for example Down syndrome) and metabolic disorders before birth. Parents can then decide on medical help.
Disadvantage: it can be misused to find the sex of the foetus, which leads to female foeticide. For this reason the law bans its use for sex determination. It also carries a small risk of miscarriage.
Step 4: Part (b): composition of Saheli:
Most oral pills contain hormones, a progestogen alone or a progestogen with oestrogen. These are taken daily for 21 days.
Saheli is a non-steroidal pill. Its active compound is centchroman. It was developed at CDRI, Lucknow.
Step 5: Part (b): advantage of Saheli:
Saheli is taken only once a week after the first three months of twice-weekly dosing. It has few side effects because it is not hormonal. It also has a high contraceptive value.
Final Answer:
(a) Amniocentesis: tests foetal cells from amniotic fluid to detect genetic disorders; advantage is early detection of disorders; disadvantage is misuse for sex determination. (b) Saheli is non-steroidal (centchroman), taken once a week, with few side effects, unlike the hormonal daily pills.
