Answer:
There is no mixing of oxygen-rich and oxygen-poor blood.
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The right atrium and right ventricle of the human heart pump oxygen-poor blood to the lungs and the left atrium receives oxygen-rich blood. They never mix.
Temperate grasslands have hot summers and cold winters. Summer temperatures can be well over 100 degrees Fahrenheit, while winter temperatures can be as low as -40 degrees Fahrenheit. They typically have between 10 and 35 inches of precipitation a year, much of it occurring in the late spring and early summer.
Answer:
<u>Option- D: </u>Is the best choice to choose from the given options.
Now, let us explain the term Cell cycle in a more comprehensive way.
<u>As the cell cycle is controlled at three checkpoints.</u>
- The integrity of the DNA is assessed at the G₁ checkpoint.
- Proper chromosome duplication is assessed at the G₂ checkpoint.
- Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint.
Explanation:
The cell cycle is controlled by three internal checkpoints that evaluate the condition of the genetic information.
- <u>The G₁ Checkpoint</u>:This stage determines whether all conditions are favorable for cell division to proceed. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into G₀ (inactive) phase and await further signals when conditions improve.
- <u>The G₂ Checkpoint:</u> The most important role of the G₂ checkpoint is to ensure that all of the chromosomes have been accurately replicated without mistakes or damage.
- <u>The M Checkpoint:</u>It occurs near the end of the meta-phase stage of mitosis. it determines whether all the sister chromatids are correctly attached to the spindle micro-tubules
Explanation:
Cancer occurs in dividing cells only because genetic materials divide into two equal portions during division. This process may be interrupted by carcinogenes or mutagenes to make mutate cells and then render them as cancer cells. In the brain, the cells are differentiated and there is no chance to start division, then how can cancer be found in the brain.
