The FLP gene can then be induced selectively, commonly using either the heat shock promoter or the GAL4/UAS system. The resulting clones can be identified either negatively or positively. In negatively marked clones, the fly is transheterozygous for a gene encoding a visible marker (commonly the green fluorescent protein) and an allele of a gene to be studied (both on chromosomes bearing FRT sites). After induction of FLP expression, cells that undergo recombination will have progeny  homozygous for either the marker or the allele being studied. Therefore, the cells that do not carry the marker (which are dark) can be identified as carrying a mutation. Using negatively marked clones is sometimes inconvenient, especially when generating very small patches of cells, where seeing a dark spot on a bright background is more difficult than a bright spot on a dark background. Creating positively marked clones is possible using the so-called MARCM ("mosaic analysis with a repressible cell marker" system, developed by Liqun Luo, a professor at Stanford University, and his postdoctoral student Tzumin Lee, who now leads a group at Janelia Farm Research Campus. This system builds on the GAL4/UAS system, which is used to express GFP in specific cells. However, a globally expressed GAL80 gene is used to repress the action of GAL4, preventing the expression of GFP. Instead of using GFP to mark the wild-type chromosome as above, GAL80 serves this purpose, so that when it is removed by mitotic recombination, GAL4 is allowed to function, and GFP turns on.
Gynecologic hemorrhage represents excessive bleeding of the female reproductive system. Such bleeding could be visible or external, namely bleeding from the vagina, or it could be internal into the pelvic cavity or form a hematoma. Normal menstruation is not considered a gynecologic hemorrhage, as it is not excessive. Hemorrhage associated with a  pregnant state  or during delivery is an obstetrical hemorrhage. Types
Metrorrhagia (metro = womb, -rrhagia = excessive flow) is uterine bleeding at irregular intervals, particularly between the expected menstrual periods. Postcoital bleeding is vaginal bleeding after sexual intercourse. Causes
Causes of gynecologic bleeding include:

Hormonal
Anovulation is a common cause of gynecological hemorrhage. Under the influence of estrogen the endometrium (uterine lining) is stimulated and eventually such lining will be shed off (estrogen breakthrough bleeding). The anovulation chapter discusses its multiple possible causes. Longstanding anovulation can also lead to endometrial hyperplasia and facilitate the development of endometrial cancer. Neoplasm
Cancer of the uterus is always a concern, specifically when the bleeding occurs after menopause. Other types of cancer include cervical cancer; bleeding in that case can sometimes be triggered by postcoital bleeding. Cancers of the vagina or fallopian tubes are rare causes of hemorrhage. Uterine fibroids represent a common, benign condition that may lead to bleeding, specifically if the lesion affects the uterine cavity. Polyps of the uterine lining are a common cause of bleeding, but such bleeding tends to be light. Trauma
Sexual assault and rape can lead to injury and gynecological hemorrhage. Accidents to the lower abdomen may lead to internal or external bleeding.