<span>At the end of prophase , nuclear membrane , nucleolus and all the cell organelles disappears and there is no distinction between the nucleoplasm and cytoplasm</span>
Answer:
In humans, genetic variations are caused because humans reproduce by a sexual life cycle which is termed as meiosis. In such a life cycle, the offspring receives half the chromosomes from the mother and half from the father. Crossing over and random assortment of chromosomes are two phenomenons which occur during meiosis. Due to these two phenomenons, genetic variations are caused.
During crossing over, the exchange of DNA segments between the homologous chromosomes takes place which brings about the genetic variations.
Explanation:
A stem cell is a cell with the unique ability to develop into specialised cell types in the body. In the future they may be used to replace cells and tissues that have been damaged or lost due to disease.