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).
Answer:
Lady Mary Wortley Montagu adapted "variolation" instead of "vaccination" to prevent smallpox in her children. She learned about it when she was in Constantinople (Turkey) with her husband. There, prisoners were intentionally inoculated with smallpox virus under their skin. When she saw that they didn't develop the disease and were among survivors, she inoculated smallpox virus to her children (son and daughter) as well using a needle. Later on, efforts of Edward Jenner towards vaccination were also recognized and it became a fashion to inoculate smallpox as a preventive measure.
Answer: Some arid-climate plants are able to conserve water because of their reduced leaf size. Less leaf surface area results in reduced water loss through the epidermis. Small leaves have fewer stomata than larger leaves, and that adaptation also reduces water loss.
Answer:
Human impact on the environment.
Explanation:
Human is the main responsible for the change in the environment. Human activities causes severe damage to the environment. The habitat of different species were destroyed by human for its own purpose. Large number of forest were eliminated for making land suitable for construction and living. Due to vehicles and industries, large amount of carbondioxide is emitted in the atmosphere which contribute in rising the temperature of the earth atmosphere. This global warming change the habitat of different organisms and these organism will die or migrate to other suitable places. Acid rain also occurs due to the emission of CO2, CO and SO2 from vehicles and industries. This acid rain causes adverse effect on the animals, plants and infrastructure or buildings.
I think it is D but I'm not sure, however, 4 seems pretty right.
