Answer:
The geosphere or geosphere is the internal and solid part of the Earth that is composed of three concentric layers called crust, mantle and nucleus. Without the geosphere, human beings cannot live on the planet, since there is no solid ground. In the Earth's geosphere are rocks, minerals, magma, sand and mountains.
This layer interacts with the other layers of the earth system, including the atmosphere, hydrosphere and biosphere, and is in a state of constant motion; Sedimentary, igneous and metamorphic rocks within the Earth's geosphere undergo continuous recycling.
It is said that the Earth formed about 4.6 billion years ago from the collision of meteoric debris that created the solar system. Due to the constant collisions during its formation, the initial temperature of the planet was extremely high; It was all molten matter.
But during the next phase of Earth's formation there was a cooling, and with it, the differentiation of the Earth's layers. Dense materials sank in the center, forming a core rich in iron and nickel. The lighter magma rose to the surface, forming the thickest layer of the Earth called the mantle.
Eventually, the outermost magma cooled to form the thin layer we call Earth's crust.
A) Crossing over is the mechanism of genetic variation that results from the exchange of gene segments between non-sister chomatids.
Scientific discovery allows us to develop new technologies, solve practical problems, and make informed decisions — both individually and collectively.
Answer/Explanation:
DNA polymerase is the enzyme responsible for replicating DNA. It is hugely important that is performs its functions accurately, as if incorrect bases are incorporated this can lead to mutations that disrupt the structure and function of genes. It adds nucleotides in a 5' - 3' direction only.
DNA polymerase III also has high processivity, which means that for every time it binds DNA, it is able to add many bases before it becomes dissociated.
A. DNA polymerase avoids the incorporation of improperly paired nucleotides in two ways:
- The first way depends on the structure of the enzyme. If the nucleotide that the enzyme is in the process of adding is not complementary to the template, then the nucleotide will not align with the template, and thus it is more inefficient to add. This inefficiency means the nucleotide is more likely to leave the active site before it is added, and DNA polymerase can replace it with the correct nucleotide.
- It also has proofreading capabilities. This means, when an incorrect base is added, it recognises the error and can fix this. It can do this because it possesses 3'-5' exonuclease activity. That means, it can chop out incorrectly added bases.
B. Ribonucleotides are the nucleotides that are incorporated into a growing RNA molecule. They are different from deoxyribonucleotides because of the differences in the sugar backbone (ribose vs deoxyribose). Their incorporation would disrupt the structure and function of the DNA, leading to problems with transcription and replication.
DNA polymerase avoids incorporating these nucleotides primarily because of the structure of the enzyme. Ribonucleotides cannot fit into the active site of DNA polymerase due to what is called a "steric filter" or "steric gate". This gate/filter function is performed by specific amino acid residues which usually have a bulky side chain and thus block the incorporation of the 2'OH of the ribose sugar (which is lacking in the deoxyribose sugar)
