Cell growth briefly at M phase when the nucleus and then the cell divide in two. The process of cell division, called cell cycle, has four major parts called phases. The first part, called G phase is marked by synthesis of various enzymes that are required for DNA replication. The second part of the cell cycle is the S phase, where DNA replication produces two identical sets of chromosomes. The third part is the G phase in which a significant protein synthesis occurs, mainly involving the production of microtubules that are required during the process of division, called mitosis. The fourth phase,
Cell-free fetal DNA available. The test can be performed at nine weeks gestation. Autosomal dominant and recessive single gene disorders which have been diagnosed prenatally by analysing paternally inherited DNA include cystic fibrosis, beta thalassemia, sickle cell anemia, spinal muscular atrophy, and myotonic dystrophy. Prenatal diagnosis of single gene disorders which are due to an autosomal recessive mutation, a maternally inherited autosomal dominant mutation or large sequence mutations that include duplication, expansion or insertion of DNA sequences is more difficult. In cffDNA, fragments of 200 300 bp length involved in single gene disorders are more difficult to detect. For example, the autosomal dominant