Answer:
The presence of an additional chromosome
Explanation:
Look at "pair" 21. See how there are THREE chromosomes instead of TWO? Normally, there would only be two chromosomes in each pair but this karyotype shows a trisomy (see def. below) of the 21st pair. This was caused by a nondisjunction mutation of the 21st pair. The is also the karyotype of a person with Down's Syndrome.
Definition of Trisomy:
A condition of the presence of three chromosomes in a pair instead of two. This normally causes developmental irregularity.
A punnet square shows you the different possible combinations and trait outcomes of the alleles.
provide the barrier that marks the boundaries of a cell.
Answer:
➢ In a mercury thermometer, <u>a glass tube is filled with mercury</u> and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts, and the temperature can be read from the scale. Mercury thermometers can be used to determine body, liquid, and vapor temperature.

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The answer u r looking for is- D* failure of the immune system to distinguish self from nonself. Hope I’ve helped ;)