Introduction to 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.

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.

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

They possess a nuclear membrane as well as membrane bound organelles in their cytoplasm.

Example : Plant & Animal Cells

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.

A nucleotide consists of a : 1. Phosphate group2. Deoxyribose sugar3. Nitrogen base: 4 types

Adenine (A)Thymine (T)Cytosine (C)Guanine (G)

DNA consists of two nucleotidechains connected together.

A & T always pair up, whileC & G do the same.

DNA Double Helix

Your genetic code is found in groups of 3 rungs in the ladder called DNA triplets

AA

TT

GG

TT

AA

CC

5’3’

5’3’

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

Supercoils

Nucleosome

DNA double helix

Histones

Coils

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.