how can I Identify the source (mechanism) and types of increased mutations in older mother oocytes and older father sperm.
Delayed parenthood has increasingly adverse effects on reproduction. In an older male, sperm quality and fertilization ability is reduced and has adverse birth outcomes. In an older female, improper oocyte cycles result in inadequate maturation of oocyte that can lead to lower live birth rates and higher miscarriage rates.
Mutations result from errors in DNA replication that occurs during cell division such as meiosis.
3-month-old female fetus contains 2 million or more primary oocytes and their development arrested in prophase I. By the time of puberty, after which one or a few oocytes complete meiosis I each month. These secondary oocytes stop meiosis again, this time at metaphase II. Meiosis is completed only if fertilization occurs. Therefore, each oocyte produced regardless of age has undergone 22 germ-cell divisions and two meiotic divisions for a total of 23 chromosome replications (the final meiotic division that occurs at fertilization, does not require DNA replication).
As a female grows older, her oocytes do not undergo any further DNA replication events. Therefore the probability of occurrence of maternal mutation is low. In contrast, spermatogenesis is a continuous process and a complex sequence of differentiation events. Therefore aging in men increases the number of chromosome replication events, which depends on the number of cell divisions.
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