What effect does Down syndrome have on the chromosomes?

Answer 1

Down syndrome is usually caused by a condition known as Trisomy 21, which means that a person has three copies of Chromosome 21, rather than the usual two copies. An extra chromosome is added. The normal amount is 46, but people with Down syndrome have 47.

Occasionally, the condition is a result of part of Chromosome 21 becoming fused to the end of another chromosome.

More info on Chromosome 21

While Chromosome 21 isn't the shortest chromosome, it is the one that contains the fewest genes (other than the Y chromosome). This is because genes on Chromosome 22 are more closely spaced, and thus the chromosome contains more genes, despite its smaller size.

Answer 2

A baby will have an extra 21st chromosome on each strain of their DNA. This means on each DNA set there are three of 21 instead of two, which is why Down Syndrome is also referred to as Trisonomy 21.

Answer 3

Down syndrome is caused by an extra copy of chromosome 21, resulting in a total of 47 chromosomes in each cell instead of the usual 46. This extra genetic material leads to physical and cognitive differences in individuals with Down syndrome.

Answer 4

You have the terms reversed. Chromosomes, or the genes within them, cause Downs Syndrome

Answer 5

No, Down Syndrome is caused by having an extra copy (three in total) of chromosome 21. This is why Down Syndrome is also known as Trisomy 21.