Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
Answer:
The majority of mutations are neutral in their effects on the organisms in which they occur. Beneficial mutations may become more common through natural selection. Harmful mutations may cause genetic disorders or cancer.
Explanation:
They are both important because mechanical has to do with physical - cause mechanical means physical, so chewing your mouth is physical (you break your food into smaller pieces physically). And then chemical digestion is when food and saliva mix together. They happen when breaking down food into nutrients - enzymes. Enzymes are important for that process, because they make a nutrient.
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