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Maternal to zygotic transition
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<p>Maternal to zygotic transition (MZT), also known as embryonic genome activation, is the stage in <a href="/facts/Embryonic_development/1lFY4EoW">embryonic development</a> during which development comes under the exclusive control of the <a href="/facts/Zygote/mSu2xMWA">zygotic</a> <a href="/facts/Genome/31Sm08JT">genome</a> rather than the maternal (egg) genome. The egg contains stored maternal genetic material <a href="/facts/MRNA/oUL6qxQn">mRNA</a> which controls embryo development until the onset of MZT. After MZT the diploid embryo takes over genetic control. This requires both zygotic genome activation (ZGA) and degradation of maternal products. This process is important because it is the first time that the new embryonic <a href="/facts/Genome/31Sm08JT">genome</a> is utilized and the paternal and maternal genomes are used in combination (ie. different <a href="/facts/Allele/8FxCS9KA">alleles</a> will be <a href="/facts/Gene_expression/alCPohLR">expressed</a>). The zygotic genome now drives embryo development. </p><p>MZT is often thought to be synonymous with <a href="/facts/Midblastula_transition/ydUQMCmA">midblastula transition</a> (MBT), but these processes are, in fact, distinct. However, the MBT roughly coincides with ZGA in many <a href="/facts/Metazoans/4b8J33nd">metazoans</a>, and thus may share some common regulatory features. For example, both processes are proposed to be regulated by the <a href="/facts/NC_ratio/Ypz2yulp">nucleocytoplasmic ratio</a>. MBT strictly refers to changes in the <a href="/facts/Cell_cycle/nLMT7K4r">cell cycle</a> and <a href="/facts/Cell_motility/5ySAMquQ">cell motility</a> that occur just prior to <a href="/facts/Gastrulation/kN8X10mK">gastrulation</a>. In the early <a href="/facts/Cleavage_(embryo)/v0osHpJC">cleavage</a> stages of <a href="/facts/Embryogenesis/1lFY4EoW">embryogenesis</a>, rapid divisions occur synchronously and there are no "gap" stages in the <a href="/facts/Cell_cycle/nLMT7K4r">cell cycle</a>. During these stages, there is also little to no <a href="/facts/Transcription_(genetics)/bDgp9HDN">transcription</a> of <a href="/facts/MRNA/oUL6qxQn">mRNA</a> from the <a href="/facts/Zygotic/mSu2xMWA">zygotic</a> <a href="/facts/Genome/31Sm08JT">genome</a>, but zygotic transcription is not required for MBT to occur. Cellular functions during early cleavage are carried out primarily by maternal products – <a href="/facts/Protein/Jxmagu3E">proteins</a> and <a href="/facts/Messenger_RNA/oUL6qxQn">mRNAs</a> contributed to the egg during <a href="/facts/Oogenesis/4yHrJAwe">oogenesis</a>. </p>