Chromosome Disorders

1.The term that means an extra or missing chromosome is Aneuploidy.
2.An example of an aneuploidy is Down syndrome.
3.A section of chromosomes gets turned around, reversing the order of the genes is Inversion.
4.Term that means identical twins is Monozygotic.

Aneuploidy
•Caused by nondisjunction during meiosis.
•Nullisomy (2n-2): Missing both copies of one chromosome
•Monosomy (2n-1): Missing one chromosome

Polyploidy-having more than two sets of chromosomes.
•Causes
-errors in meiosis: results in diploid gametes
-events at fertilization: dispermy- two sperm cells penetrate and fertilize the egg.

Human Chromosome Disorders
Monosomy
Missing one chromosome from a pair
•Rare in live births
•turner syndrome (45, x): xo female. The female is missing an x chromosome
•causes-nondisjunction in meiosis or mitosis




Notice in the picture that the last chromosome only contains one allele when it should have two.


Trisomy (more common than monosomy)
Trisomy is an abnormality in which there are three copies, instead of two, of chromosomes. It is a type of aneuplodiy
•13 (Patau Syndrome)
-cleft palate, eye defects…
•18 (Edward Syndrome)
-small birth weight, slow growth
•21 (Down Syndrome)
-translocation of chromosome 21 (usually)
• Deletion of chromosome 15
-Cri-du-chat & Pradar-willi syndrome
Translocation (one piece changes play but the other doesn’t. It is deletion)