Zachary Knott Biology 101

 The nucleus is the cell’s control center  It issues instructions to that control cell activities  It stores hereditary information

 Nuclear envelope: special kind of membrane that bounds the surface of the nucleus  Acts as a barrier between the nucleus and the cytoplasm, but substances need to pass through it  Nuclear Pores: openings that form when the two membrane layers pinch together

 The DNA of eukaryotes  Form by dividing into several segments and associating with protein  After cell division the chromosomes uncoil forming threadlike structures called chromatin  The chromatin is then available for protein synthesis

 Cite for several hundred genes that encode rRNA  rRNA: ribosomal RNA  Where ribosome subunits assemble

Nucleolus Nuclear Envelope Nuclear Pores Chromatin Chromosomes

 Huntington’s Disease  Caused by a faulty gene being present on chromosome 4  Having the faulty gene leads to damage of the nerve cells in areas of the brain  Result: gradual physical, mental, and emotional changes The Huntington Disease Association

1. What is chromatin? A. A barrier between the nucleus and the cytoplasm B. The place where ribosome subunits assemble C. Uncoiled DNA that is used in protein synthesis D. The cell’s control center 2. What is the role of nuclear pores? A. A special kind of membrane that bounds the surface of the cell B. It contains proteins that allow RNA in and out of a the cell C. Forms a barrier between the nucleus and the cytoplasm allowing certain to pass through it D. Openings that form when two membranes pinch together