Down syndrome in humans is due to of the 21 st chromosome.

Down syndrome in humans is due to ADDITIONAL, PARTIAL OR FULL COPY of the 21 st chromosome.

Explanation:

Down syndrome is a genetic disorder in which an individual has a total of 47 chromosomes instead of 46 that is, 23 pairs of chromosomes which is found in normal individuals. This occurs as a result of the presence of additional, partial or full copy of chromosome 21. There are generic variations that occurs in chromosome 21 leading to down syndrome, these include:

-->Trisomy 21 : the individual has three copies of chromosome 21 instead of two copies due to abnormal cell division that occurred during development of sperm or egg.

--> Mosaic Down syndrome: the individual has some cells with an extra copy of chromosome 21 and it's caused by abnormal cell division after fertilization.

--> Translocation down syndrome: This type of down syndrome occurs when chromosome 21 gets attached to another chromosome which occurs during or after conception.

Generally the symptoms due to the presence of this extra genetic material includes:

--> short heights

--> poor muscle development

--> short neck

--> short fingers with small hands and feet

--> increased risk to development of dementia

--> greater tendency to develop obesity

lysosome is this part of the cell is surrounded by a very thick outer membrane to protect the rest of the cell from its strong enzymes.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."