Question

what is blastocyst

PART IV 57 Name Section Mitosis Meiosis TABLE 10.2 TSI Human Organism Location where does it take place in the body? Number of cells formed at the end of mitosis and meiosis II. Number of chromosomes pres- ent at the end of the cell division cycle (mitosis and meiosis II). Does the process increase genetic diversity? List two examples of how genetic variation is accomplished. Crossing over-Does it occur? If so, name the stage it occurs. mie is best described as

Answer 1

	Mitosis	Meiosis
Location	The mitosis is a process which divides the somatic cells into two daughter cells that are genetically identical to each other. The mitosis occurs within the nucleus of the cell.	The meiosis is a process in which the gametic or germ cell divides and produces cells which are not genetically identical. This process occurs within the primordial germ cells and they help with sexual reproduction.
Number of cells formed at end	At the end of mitosis, it is responsible for production of two daughter cells that are identical to each other.	At the end of meiosis II, it tends to form four gametic cells which are haploid in nature.
Number of chromosomes at end	At the end of mitosis, it produces 2n or diploid chromosome and hence consists of 46 chromosomes. In human cells, there are 23 pair of chromosomes produced at end of mitosis.	At the end of meiosis, it produces 4 cells and each of it consists of half the chromosome number. During the end of meiosis I, it consists of 23 chromosome and total of 46 chromatids. At the end of meiosis II, the chromosome is further halved and it consists of 23 chromatids.
Example of genetic variation	Generally, genetic variation does not take place in mitosis.	i)DNA swapping is one of the causes which can cause genetic variation in daughter cells. Generally this happens in prophase I when there is crossing over that happens between homologous chromosome and a chromatid might break and reconnect again, introducing genetic variation. Basically there is exchange of chromosome segment which takes place between non-sister chromatids. Hence crossing over is one example. ii) Random segregation is another way in which chromosomes are shuffled between the four gametes and this can introduce genetic variation.
Crossing over	In the mitosis, crossing over rarely takes place.	Yes, it takes place in meiosis and it leads to introduction of genetic variation. It is basically the exchange of genetic material that takes place between two homologous chromosome and non-sister chromatids, usually takes place during prophase I.

Blastocyst is a structure which is formed during the early developmental period and it consists of an inner cell mass which leads to the formation of embryo. It forms from the 16-cell stage of morula and forms blastocyst which consists of the inner cell mass which gradually forms the inner cell mass and outer layer is known as trophoblast. The blastocyst formation in humans starts after 5 days of fertilization and it is a fluid filled cavity formed from morula. After a week of fertilization, the blastocyst is implanted into the endometrium of uterine wall which further starts the process of gastrulation forming three germ layers – endoderm, ectoderm and mesoderm.