Answer:
Crossing over or recombination
Explanation:
Crossing over or genetic recombination is a stage in the late prophase of meiosis I where homologs lie close to each other in pairs to exchange chromosomal material creating new combination of genes as each homologs is derived from either the father or the mother.
This exchange determines the material to be inherited by the offspring producing genetic variation which males the offspring typically different from the parents (genetic variation).
They are prokaryotic cells....
Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess water, from rain, snowmelt, or other sources flow over the land. This is a major component of the water cycle or the hydrological cycle.
Active transport could transport material across the membrane against the concentration gradient
Answer:
Germ cells are highly specialized cells that form gametes, and they are the only cells within an organism that contribute genes to offspring. Germline stem cells (GSCs) sustain gamete production, both oogenesis (egg production) and spermatogenesis (sperm production), in many organisms. Since the genetic information contained within germ cells is passed from generation to generation, the germ line is often referred to as immortal. Therefore, it is possible that germ cells possess unique strategies to protect and transmit the genetic information contained within them indefinitely. On the other hand, it was shown that germ cells are pluripotent in all stages of development. We and other groups succeeded in the long-term culture of spermatogonial stem cells (SSCs) of mice. The cells were phenotypically similar to the ES/embryonic germ cells except for their genomic imprinting pattern. They differentiated into various types of somatic cells in vitro under the conditions used to induce the differentiation of the ES cells, and the SSCs formed germline chimeras when injected into blastocysts. Furthermore, we have shown that somatic stem cells are able to differentiate to germ cells. Derivation of both male and female gametes in vitro raises the possibility of using these gametes to gain a better understanding of basic reproductive biology and, in particular, to extend the potential for therapeutic cloning, transgenic technologies and the treatment of infertility. We started three different approaches for establishment of the in vitro gametogenesis systems: 1) ES-derived gametogenesis, 2) derivation of germ cells from somatic stem cells and 3) in vitro gametogenesis based on cultured spermatogonial stem cells. We developed a strategy for the establishment of germline stem cell lines from embryonic stem cells. These cells are able to undergo meiosis, generate haploid male gametes in vitro and are functional, as shown by fertilization after intra-cytoplasmic injection into mouse oocytes. Molecular and cellular mechanisms underlying differentiation of ES to functional gametes should be elucidated in future research. In other approach, we show that bone marrow stem (BMS) cells are able to trans-differentiate into male germ cells. BMS