Ash, green, and red (Fraxinus spp.)âThe common. leaf spot and scorch on ash leaves is caused by the ash. anthracnose fungus, Gloeosporium aridum. Large areas of. infected leaves, especially along the edges, turn brown (Figure. 2). Premature leaf drop may occur.
How sperm and eggs develop precisely 23 chromosomes each. April 12, 2012. There are many tools that cells could use to separate DNA strands that cross over during meiosis. UC Davis researchers have identified the right tools for the job. Researchers at the University of California, Davis have discovered a key tool that helps sperm and eggs develop exactly 23 chromosomes each.
Sperm and eggs are sex cells. Meiosis is the start of the process of how a baby grows. Normally, meiosis causes each parent to give 23 chromosomes to a pregnancy. When a sperm fertilizes an egg, the union leads to a baby with 46 chromosomes. But if meiosis doesnât happen normally, a baby may have an extra chromosome (trisomy), or have a missing chromosome (monosomy).