Cytology Objectives: 1. What is Cytology? 2. Explain how prokaryotic & eukaryotic cells differ. 3. What is DNA? 4. Identify the parts and function of the Nucleus.

What is Cytology? It is the study of the structure and function of cells. The cell is the basic structural and functional unit of life so therefore cytology is the fundamental most important topic in all of biology.

Cytoplasm : area of space outside the nucleus; contains the organelles & cytosol. Organelles : are tiny structures in the cytoplasm which perform various jobs for the cell. Cytosol : is the fluid part of the cytoplasm.

Prokaryotic Cells They lack a nuclear membrane as well any other membrane covered organelles in their cytoplasm. Considered to be “Primitive Cells” Example : Bacteria & Blue- Green Algae

Eukaryotic Cells They possess a nuclear membrane as well as membrane bound organelles in their cytoplasm. Example : Plant & Animal Cells

The Nucleus is the computer or control center of the cell. contains the genetic material of life DNA (Deoxyribonucleic acid). discovered by James Watson, Francis Crick, & Rosalind Franklin (1953). a DNA molecule consists of nucleotides connected together.

Nucleotide A nucleotide consists of a : 1. Phosphate group 2. Deoxyribose sugar 3. Nitrogen base: 4 types Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DNA consists of two nucleotide chains connected together. A & T always pair up, while C & G do the same.

DNA Double Helix DNA is a double helix in which two strands are wound around each other. Each strand is made up of a chain of nucleotides. The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.

DNA Your genetic code is found in groups of 3 rungs in the ladder called DNA triplets 5’ 3’ C G A T Identify 5 prime (exposed phosphate) and 3 prime (no exposed phosphate) T A 3’ 5’

Assignment Complete the worksheet entitled “ODE to DNA” .

Long chains of DNA form Chromatin. Short sections of DNA along a piece of chromatin form Genes. Human genome contains about 30,000 genes! A gene will either produce or influence a specific trait in the offspring.

Chromatin Chromatin Nucleosome DNA double helix Coils Supercoils Eukaryotic chromosomes contain DNA wrapped around proteins called histones. The strands of nucleosomes are tightly coiled and supercoiled to form chromosomes. Histones

Nucleolus / Nucleoli (plural) : a dark spherical structure that is the site of ribosome formation. Ribosomes and other important chemical messages leave the nucleus through the Nuclear Pores. The membrane around the nucleus is called the Nuclear Membrane or Envelope.