Zachary KnottBiology 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

NucleolusNucleolusNuclear Nuclear EnvelopeEnvelope

Nuclear PoresNuclear Pores

ChromatinChromatinChromosomesChromosomes

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 http://www.hda.org.uk/charity/whatishd.html

1. What is chromatin?A. A barrier between the nucleus and the cytoplasmB. The place where ribosome subunits assemble C. Uncoiled DNA that is used in protein synthesisD. 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 cellB. 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 itD. Openings that form when two membranes pinch

together