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).
B. Viruses are not living.
A virus is nothing more than a packet of genetic material that does not display the characteristics of living organisms.
Answer:
As comic is not available, lets try to understand genetic drift generally.
Explanation:
Genetic drift can be described as the changes in the allele frequency or changes in the genotype variations of a population due to certain reasons such as death etc. In genetic drift, a particular genotype of a species starts to decrease, while the other genotype might start to increase. For example, imagine there are 6 colours of rabbits to be seen in a population. An event such as a diseases takes over which results in death of most of the rabbits. Only a few rabbits are left having brown and grey colour. Hence, the genetic drift changes from 6 to only 2.
Answer:
D. All cells must be reproduced by another cell.
Explanation:
The cell theory has a couple key components, which are as follows:
#1. Cells are the basic unit of life.
#2. Cells have hereditary data that is passed down to their offspring.
#3. All cells come from preexisting cells.
#4. All organisms, both unicellular and multicellular, are made of one or more cells.
#5. Energy flows through cells.
#6. All cells have a similar composition.
Answer:
Magnetic reversals
Explanation:
When the Earth's magnetic field reverses, a new stripe, with the new polarity, begins. Such magnetic patterns led to recognition of the occurrence of sea-floor spreading, and they remain some of the strongest evidence for the theory of plate tectonics.
Have a great day!! Hope this helps!!
