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.
The sperm cell and the egg cell that come together to form the zygote each contain half the normal amount of DNA. There are 46 chromosomes in a typical human cell. The sperm and the egg each contain only 23 - one copy of chromosomes 1 through 22 plus an X or a Y. Egg cells can only contain an X but the sperm can contain an X or a Y. East Haven High School in CT (10th grade student)