As it turns out, March is Trisomy Awareness Month. I’ll try to post some facts on it even though I’m still trying to learn more about it myself, with my very rusty knowledge from college biology.
Chromosomes are thread-like structures located in the nucleus of a cell. They are made of protein specially structured to hold tightly coiled DNA. The DNA is what contains our genes. Humans have 23 pairs of chromosomes, a copy from each parent, resulting in 46 total. Trisomy occurs when there are three copies of a particular chromosome. Finn had three copies of chromosome 9.
The most severe chromosome disorders are numerical abnormalities caused by the loss or gain of whole chromosomes, which can affect thousands of genes. The chromosomes are numbered from largest to smallest in size (1 to 22). The largest chromosomes contain the most genes. With Trisomy, the smaller the chromosome number impacted, the more severe the effect on development, since more genes are impacted. Half of all miscarriages are due to chromosomal abnormalities. Numerical abnormalities are sporadic, and they do not usually recur in subsequent pregnancies. Most Trisomy 9 babies are miscarried in the first trimester, so it is difficult to estimate how many babies are affected and there isn’t a lot of information on it. Finn was a strong little baby to survive to late preterm (35 weeks)!
A karyotype describes the chromosome count that an organism has. A normal human karyotype contains 22 pairs of autosomal chromosomes and one pair of sex chromosomes (allosomes), making 46 total chromosomes. Normal karyotypes for females contain two X chromosomes and are denoted 46,XX; males have both an X and a Y chromosome which is denoted 46,XY. Since Finn was a boy with Trisomy 9 , his karyotype would be (47, XY, +9), indicating there were 47 total chromosomes with an extra 9th chromosome.