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.
As mentioned above, photosynthesis converts carbon dioxide from the air to. carbohydrates and other kinds of ï¬xed carbon and releases oxygen to the atmosphere. When we burn ï¬rewood, ethanol, or coal, oil and other fossil fuels, oxygen is consumed, and carbon dioxide is released back to the atmosphere.