(a) (A) Amniocentesis : It is also known as amniotic fluid test. This test detects chromosomal abnormalities in the fetus. After 16 weeks of pregnancy, sample of amniotic fluid is taken from amniotic sac and its DNA is examined for genetic abnormalities.
(B) Lactational amenorrhea : Absence of menstruation during the intense lactation following delivery. This period is used as a contrceptive method upto six months following delivery as long as the mother breast-feeds the child.
(C) ZIFT : Zygote intra fallopian transfer in an invitro fertillization (IVF) technique where the zygote or early embryo having upto 8 blastomeres is transferred into the fallopian tube to complete its further development.
(a) Apomixis is a special mechanism of production seeds by flowering plants without fertilisation. Apomictic seed can develop.
(i) Diploid egg cell is formed without reduction division which develops into the embryo without the fertilisation. Example - Grassesss.
(ii) Nucellar cells surrounding hte embryo sac divide and protrude into the embryo sac and develop into embryos. Example - citrus and mango.
(b) Apomixis makes use of hybrid seed more economical. Apomixis provides on opportunity to the farmers to keep using same hybrid seeds year after year and not buy hybrid seed every year. One disadvantage of apomictic seeds is that it reduces genetic diversity from parent to offsprings due to lack of variations in asexual reproduction.
(c) Hybrid seeds production is costlier because it novolves cross pollination of plants in an artificial manner. If require lots of scientific research, scientists try thousands of combinations of parents to identify a desired hybrid. It also takes a lot of time (nearly 10 years) to develop hybrid seeds. Hybrid seed production also require complete isolation.
