Answer:
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Explanation:
DNA is composed of nucleotides, which are composed of three parts:
1. A five carbon carbohydrate (pentose)
Pentose is classified as a monosaccharide (simple carbohydrate), and its molecular formula is represented by 
. They are water soluble molecules with sweet taste. Monosaccharides may have from three carbon atoms (trioses) to six (hexoses). In DNA is present pentose (5 carbon atoms)
2. A nitrogenous base
Nitrogenous bases are ring-shaped compounds that contain nitrogen in their molecular structure. They are classified into two groups: purines and pyrimidines
The purine bases are adenine (A) and guanine (G). They are larger and contain more than one ring in their structure,.
The pyrimidines, cytosine (C), uracil (U) and thymine (T), are smaller and composed of a single ring.
3. One or more phosphate groups
A phosphate consists of a trivalent anion that contains one phosphorus atom and four oxygen atoms. Its molecular formula is expressed by 
.
Oxygen and nutrients from the mother's blood are transferred across the placenta to the fetus through the umbilical cord. This enriched blood flows through the umbilical vein toward the baby's liver. There it moves through a shunt called the ductus venosus. This allows some of the blood to go to the liver.
A small amount of the blood continues on to the lungs. Most of this blood is shunted through the ductus arteriosus to the descending aorta. This blood then enters the umbilical arteries and flows into the placenta. The oxygen rich blood then returns to the fetus via the third vessel in the umbilical cord (umbilical vein). The oxygen rich blood that enters the fetus passes through the fetal liver and enters the right side of the heart.
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The atmosphere is the part of the carbon and water cycles but absent from the phosphorous cycle. Carbon cycle depends on photosynthesis and respiration. Water cycle connects aquatic and terrestrial biomes.
