Answer:
1. They must be removed before sister chromatids or homologous chromosomes can separate
Explanation:
During the S-phase of the cell cycle, not only does DNA have to be replicated, but also newly synthesized DNA molecules have to be connected with each other. This replicated DNA (sister chromatids) remain physically connected with each other from S phase until metaphase. This physical connection is called Sister chromatids cohesion.
Sister chromatid cohesion depends on COHESIN, a tripartite protein complex that forms a ring structure to hold sister chromatids together during mitosis and meiosis. Cohesin regulates the separation of sister chromatids during cell division, either mitosis or meiosis. This sister chromatid cohesion is essential for the biorientation of chromosomes on the mitotic or meiotic metaphase spindle, and is thus an essential prerequisite for chromosome segregation. Without the cohesion, sister chromatids would not be segregated symmetrically between the forming daughter cells, resulting in aneuploidy.
Cohesion is established during S-phase of DNA replication, and the cohesins hold the sister chromatid together after DNA replication until anaphase when the removal of cohesin leads to separation of sister chromatids (meiosis II and mitosis) and homologous chromosomes (meiosis I).
Isotopes are elements with same atomic number Z= number of protons but different mass number A, where A= Z+N, N= number of neutrons which is variable. As for radioisotopes, I’ve never heard of them before !
True
Fossil fuels like coal and petroleum takes millions of years to form. The rate of usage of fossils is not equal to its formation. As the rate of formation is slow it is important to use energy in an efficient way so that it is not consumed in a wrong way. The transformation of energy should be more efficient to avoid the wastage of energy. By doing this we can decrease the consumption of fossil fuels as it cause pollution in the environment. The burning of fossil fuel releases carbon dioxide, nitrogen oxide ,and other harmful gases which is injurious to the health of people. So, the fossil fuel should be used in a decreased manner.
