<span>B. A prokaryotic cell does not have nucleus and the other one does. The most defining characteristic of eukaryotic cells is their true nucleus. Prokaryotes lack true nucleus</span> and membrane bound organelles.
That is when extinction occurs. Hope I helped!
Natural Selection.
It favors the better adapted organisms.
Answer: There is presence of tumor.
Explanation: The adhesion of cells to extracellular matrix (EMC) through integrins ( cell-EMC binding molecules, which are collagens, laminins and fibronectin) causes the activation of kinases in the cytoplasm.
However, kinanes helps in controlling the epithelial cell differentiation and upholding the epithelial tissues. This is done by the addition of phosphate groups to a substrate protein which is termed Protein phosporylation. Then, the kinases direct the affairs of the cell and it's activities. For example, it determines the cell division, anabolic and catabolic activities of the cell, movement of ions between the cell and it's environment (signal transduction), protein functions and etc.
Conclusively, since the activities of the cell like cell division and protein functions is dictated by the kinase, reduction in cell division that gave rise to rapid growth is put on hold. Hence, the tumor is been suppressed.
Note: the binding of cell-EMC is regulated by Transforming Growth Factor (TGF) β.
Answer:
DNA replication a process of copying of a cell's DNA. DNA replication is semiconservative process which means that each strand in the double helix helps in the synthesis of new, complementary strand and conserve the parent template.
The Molecular mechanism of DNA replication is as following:
- The double starnded DN in binded with hydrogen bond, the enzyme helicase opens up the DNA at the replication fork.
- A single stranded binding protein prevent the rewinding of DNA and so binds to the DNA around the replication fork
- Topoisomerase prevent supercoiling at replication fork.
- The ezymes primase come in action and produces RNA primers which are complementary to the DNA strand.
- DNA polymerase III help to extends the primers and allow them to add to the 3' end, to make new DNA.
- DNA Polymerase then remove RNA primers and replace with DNA.
- DNA ligase blocks the the gaps between DNA fragments.
So, this is the molecuar mechanism of DNA replication.
