Chromosomal Mutation: Down Syndrome
If you look at the picture above, you can immediately see an asymmetrical Chromosome pair (triplet in this case). This is the widely-recognized cause of Down Syndrome, an extra chromosome.
Down syndrome is usually caused by an error in cell division called nondisjunction. (see below pic and explanation)
This is a chromosomal deletion syndrome. What's happening is a part of the chromosome breaks off and is deleted. It happens whenever there is something wrong with karyotyping. Because of this, it effects the phenotype.
Down syndrome is usually caused by an error in cell division called nondisjunction. (see below pic and explanation)
This is a chromosomal deletion syndrome. What's happening is a part of the chromosome breaks off and is deleted. It happens whenever there is something wrong with karyotyping. Because of this, it effects the phenotype.
As you can see above, nondisjunction happens when a pair of chromosomes fails to separate during egg (or sperm) formation. When that egg unites with a normal sperm to form an embryo, the embryo ends up with three copies of chromosome 21 instead of the normal two. The extra chromosome is then copied in every cell as the baby develops.