However, in spermatogenesis the ability to repair DNA damages decreases substantially in the latter part of the process as haploid spermatids undergo major nuclear chromatin remodeling into highly compacted sperm nuclei. As reviewed by Marchetti et al., the last few weeks of sperm development before fertilization are highly susceptible to the accumulation of sperm DNA damage. Such sperm DNA damage can be transmitted unrepaired into the egg where it is subject to removal by the maternal repair machinery. However, errors in maternal DNA repair of sperm DNA damage can result in zygotes with chromosomal structural aberrations.Melphalan is a bifunctional alkylating agent frequently used in chemotherapy. Meiotic inter-strand DNA damages caused by melphalan can escape paternal repair and cause chromosomal aberrations in the zygote by maternal misrepair. Thus both pre- and post-fertilization DNA repair appear to be important in avoiding chromosome abnormalities and assuring the genome integrity of the conceptus. Detection
Depending on the information one wants to obtain, different techniques and samples are needed. For the prenatal diagnosis of a foetus, amniocentesis, chorionic villus sampling or circulating foetal cells would be collected and analysed in order to detect possible chromosomal abnormalities. For the preimplantational diagnosis of an embryo, a blastocyst biopsy would be performed. For a lymphoma or leukemia screening the technique used would be a bone marrow biopsy. See also
Aneuploidy
Chromosome segregation
Genetic disorder
List of genetic disorders
Gene therapy
Nondisjunction
Obstetrical complications

References
External links
Chromosome+disorders at the US National Library of Medicine Medical Subject Headings (MeSH)
Children with impetigo can return to school 24 hours after starting antibiotic therapy as long as their draining lesions are covered. Treatment
Antibiotics, either as a cream or by mouth, are usually prescribed. Mild cases may be treated with mupirocin ointments. In 95% of cases, a single 7-day antibiotic course results in resolution in children. It has been advocated that topical antiseptics are inferior to topical antibiotics, and therefore should not be used as a replacement. However, the National Institute for Health and Care Excellence (NICE) as of February 2020 recommends a hydrogen peroxide 1% cream antiseptic rather than topical antibiotics for localised non-bullous impetigo in otherwise well individuals. This recommendation is part of an effort to reduce the overuse of antimicrobials that may contribute to the development of resistant organisms such as MRSA. More severe cases require oral antibiotics, such as dicloxacillin, flucloxacillin, or erythromycin. Alternatively, amoxicillin combined with clavulanate potassium, cephalosporins (first-generation) and many others may also be used as an antibiotic treatment. Alternatives for people who are seriously allergic to penicillin or infections with methicillin-resistant Staphococcus aureus include doxycycline, clindamycin, and trimethoprim-sulphamethoxazole, although doxycycline should not be used in children under the age of eight years old due to the risk of drug-induced tooth discolouration. When streptococci alone are the cause, penicillin is the drug of choice.When the condition presents with ulcers, valacyclovir, an antiviral, may be given in case a viral infection is causing the ulcer. Alternative medicine
There is not enough evidence to recommend alternative medicine such as tea tree oil or honey.