HD is called an autosomal dominant disorder because only one copy of the defective gene, inherited from one parent, is necessary to produce the disease. The genetic defect responsible for HD is a small sequence of DNA on chromosome 4 in which several base pairs are repeated many, many times.
Carbon dioxide cannot pass through the protective waxy layer covering the leaf (cuticle), but it can enter the leaf through an opening (the stoma; plural = stomata; Greek for hole) flanked by two guard cells. Likewise, oxygen produced during photosynthesis can only pass out of the leaf through the opened stomata.
It is produced during the light reaction of photosynthesis. Explanation: Photosynthesis comprises of two main stages, the light reaction (also known as Hill reaction/photolysis of water) and the dark reaction (also known as the Calvin Cycle/reduction of carbon dioxide). However, the production of oxygen only occurs in during the light reaction, which takes place in the grana of chloroplasts. During the light reaction, chlorophyll captures light energy which excites the electrons of the chlorophyll molecules to higher energy levels.