phosphorylase, which is a key enzyme to mobilize glucose from stored glycogen, through phosphorylation. Glycogen is the polymer storage unit of glucose in the body. When the body requires energy it can use enzymes such as PHK to break down the glycogen into glucose for the body to use. Some symptoms of the disease are altered blood glucose levels, ketoacidosis, growth retardation, or liver distention. Recurrent miscarriages Skewed X-chromosome inactivation has been implicated in miscarriages in the past. Recurrent pregnancy loss can be defined as either two or three consecutive lost pregnancies within five months. In most cases, the loss of pregnancy can be attributed to genetic, hormonal, anatomical and immunological problems. However, there are still about 50% of cases without a known cause. A study hypothesized that skewed X-inactivation may play a role in these miscarriages. However, a 2003 study found that there was no significant correlation between miscarriages and skewed X-inactivation, with only 6.6% of the patients showing significant skewing as compared to the 3.9% rate in the control group. It also stated that there had been a lack of controlling for age-related skewing in similar studies and concluded that it is unlikely for skewed X-inactivation to influence recurrent miscarriages. Studying skewed X-inactivation To study skewed X chromosome inactivation, there must be a detectable difference between the two parental chromosomes. This difference, or polymorphism, will allow detection of which chromosome is active in the cell, so an inactivation ratio can be determined. Often, the methylation levels of the inactive DNA are detected in order to identify the inactive chromosome. Loci that are known to be polymorphic within the human population are selected. Assays that detect the methylation level of the highly polymorphic CAG trinucleotide at the 5’ end of the androgen receptor gene are often used in skewed X-inactivation studies. Other loci used include phosphoglycerate kinase, hypoxanthine phosphoribosyl transferase and the DXS255 locus. If these loci contain heavy methylation, it indicates the chromosome is inactive. At the turn of the 21st century, ratio detection moved to more direct methods by using mRNA or protein levels, and whole exome sequencing. With the exception of escaped genes, only the active X chromosome will transcribe mRNA and produce protein. The exome sequencing provides a dataset that shows target sequences, giving an indication of disease-related protein coding regions. mRNA sequencing is then used on these regions to focus on the X chromosome