I. Nucleus

A. Center of the cell

B. Control Center for all cell functions

1. Controls Growth

2. Controls division of cell

C. Consists of 3 main components

1. The nuclear envelope

a. consists of 2 membranes

2. Chromatin

3. Nucleuous (see III)

C. Oval-Shaped

D. Enclosed by two-layered membrane

E. Contains a liquid called nucleoplasm as strands of DNA covered with a coating of protein

F. Contains structure that transmits hereditary traits (Chromosomes)

II. Chromosomes

A. Microscopic thread like part of the cell

B. Located in Nucleus

C. Shaped like rods and must be stained to be seen clearly in a microscope

D. Consists of DNA and RNA

E. Varies in shapes and sizes

F. Usually occurs is pairs (example see Disorders, Down Syndrome)

G. Every different species has a characteristic number of chromosomes called a chromosome number

1. People usually have 46-48 chromosomes (23 pairs)

C. Carries hereditary information in forms of genes that determines qualities of an animal or person

1. Male (XY chromosomes) or female (XX chromosome)

2. Blue or brown eyes or tall or short

3. Sex-linked disorders-(healthy females may sometimes carry defective genes on an X chromosome, but a female rarely inherits two defective X chromosomes. Usually are expressed in males who have only one X chromosome.)

a. Hemophilia-(Blood doesn't clot properly causing extensive bleeding)

b. Muscular dystrophy- (Muscles deteriorate after time)

4. Chromosomes abnormalities-(can occur from structural defects in the Chromosome or from either having more or fewer then the normal 46 chromosomes)

a. Down Syndrome- (formally called mongolism) caused by an extra 21st chromosome

i. Mental retardation is moderate to serve

ii. Physical differences include small skull, a short flat- bridged nose, and usually short fingers and neck

5. Sex chromosomes aberrations

a. Turner's syndrome- (one of the two X chromosomes is absent in the female.

i. result in short, blocky physique and lack of sexual development

b. Klinefelter's syndrome- (the male usually has two X chromosomes, instead of one, and one Y chromosomes

i. result in small genitals, lack of sperm formation, late puberty, and, occasionally breast development

III. Nucleolus

A. At least one nucleolus is present in the nucleus of most cells

B. Takes part in protein synthesis

C. Consists of:

1. ribosomal RNA

2. protein

3. ribosome's in various stages of synthesis and DNA

D. Is where the nucleoproteins are assembled

E. Contains a concentration of RNA

1. Biologists think that RNA is made initially in the nucleus and are stored there.