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.
The red-green color blindness is a recessive X-linked trait. The females are not affected unless both the X chromosomes have the affected allele. Mostly, the females are the carriers, and the males are affected as they have only one X chromosome. In the given pedigree, the father of Irene have the normal allele, while her mother is a carrier. However, Irene is neither a carrier nor affected. This means that she carries normal alleles on both X chromosomes. Hence, her allele combination is 
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The correct answer is vacuole. Vacuole controls the water input and water output of an amoeba. It is found within endoplasm. The vacuole is an essential part of an amoeba because it maintains the life of an amoeba. Malfunction can cause the amoeba to burst.
Hey there!
<span>The near extinction of many bird species was caused by:
Answer: </span>
<span> use of DDT
Hope this helps
Have a great day (:
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A im guessing? soz if i get it wrong.
