The hydrogen bonding of nucleotides into a new DNA molecule is facilitated by enzymes. Hydrogen bonding is the electromagnetic attraction between polar molecules in which hydrogen is bound to a larger atom, such as oxygen or nitrogen. The nucleotides in a base pair are complementary which means their shape allows them to bond together with hydrogen bonds. The A-T pairs forms two hydrogen bonds while the C-G pair forms three. The enzymes called DNA polymerases join the nucleotides by way of phosphodiester bonds.
Melanin provides pigmentation to the skin and it also provides UV ray protection (which is its role in the epidermis).
Answer:
Pregnancy, which is characteristically associated with changes in hormone levels in the body is a process tightly regulated by the hormon Human Chorionic Gonadotropin
Explanation:
The so-called pregnancy hormone is the Human Chorionic Gonadotropin (HCG). It only occurs during the gestation period and is responsible for regulating the entire process. Segregated by the placenta, it can be found in urine and blood.
The presence of the hormone in the urine allows to confirm the pregnancy with the test. As in pregnancy, the placenta begins to form, the cells that make it up begin to stimulate the production of HCG, which causes the hormone levels to increase very rapidly in the first trimester of pregnancy
Explanation:
The speed of water in a stream is affected by the gradient of the geography. The steeper the geography the higher the speed of the water flow and the higher the erosion capacity of the stream. This means the stream will be narrow and deep. There is also less meandering of the stream.
When the gradient is less steep, the stream flow slows down and so does the erosion force it bears especially on the river bed. This therefore result in a higher horizontal erosion than vertical erosion. The steam becomes wide and shallow. The stream is also more likely to meander.
The volume of water in the stream also affects the size, shape, and flow of streams and rivers. A higher volume of water has more erosion power due to the weight of the water column. The stream is, therefore, more likely to be bigger in size than a stream that carries low water volume.
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