Upwelling brings greater concentrations of dissolved nutrients to the ocean surface
<span>#1) With reference to the role of oncogenes, explain how the normal controls over the cell cycle can be lost.
Answer: The way that cell cycle can be lost is by going through changes in the activity of cell cycle regulators. Cancer causes different types of mutations. There are two types of cell cycle regulators that can promote the development of cancer:
-Positive Regulators that can be over activated (become oncogenic).
-Negative Regulators (tumor suppressors) which can be inactivated.
I hope it helps, Regards. <span /><span>
</span></span>
The bond formed between the sugar of one nucleotide and the phosphate of an adjacent nucleotide is a covalent bond. A covalent bond is the sharing of electrons between atoms. A covalent bond is stronger than a hydrogen bond (hydrogen bonds hold pairs of nucleotides together on opposite strands in DNA).
<span>LD
means lethal dose. LD50 is the amount of a material, administered at once to
cause the death of half (50%) of a group of test organisms. A test which shows that LD50 of a certain
chemical is 20 mg per kg means that 20 milligrams of that chemical for every 1
kilogram body weight of the test animal when administered in one dose, causes
the death of 50% of the test group.</span>
