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.
1 In a human egg or sperm, there are 23 chromosomes, one of which is an X or Y. 2  The number of chromosomes is reduced from 46 to 23 during the process of meiosis. 3  Fertilization of the egg by the sperm restores the diploid number of 46 chromosomes. All cells in a higher eukaryote (like us) are diploid Â­ EXCEPT ...for the germ cells Â­ eggs and sperm. 2  Germ cells have only half the number of chromosomes as a diploid cell Â­ one of each pair-and are termed haploid (n) .