Introduction to Molecular BiologyFirst Week

Gihan E-H Gawish, MSc, PhDAss. Professor

Molecular Genetics and Clinical Biochemistry

KSU

Molecular BiologyWhat is the molecular biology science? And

Why it is important to study?!

Molecular biology; the study of gene structure

and functions at the molecular level to

understand the molecular basis of hereditary,

genetic variation and the expression patterns of

genes

Molecular Biology

DNA the molecule of life

The totality of genetic information and is encoded in the DNA (or, for some viruses, RNA)

The Genome

Deoxyribonucleic Acid (DNA)

The genetic material of all cellular

organisms and most viruses, the

gigantic molecule which is used to

encode genetic information for all

life on Earth.

The Chromosomehttp://www.johnkyrk.com/chromosomestructure.html

The storage place for all genetic information, the number of chromosomes varies from one species to another.

In normal human cell

DNA contained in the

nucleus, arranged in 23

pairs of chromosomes.

22 pairs of chromosomes

(autosomes); the 23

chromosome pair

determines the sex of

individual and is composed

of either two (x)

chromosomes (female) or

an (x) and (y) chromosome

(male).

Genes located on

chromosome on it's place

or locus.

Base composition of DNA varies from one species to another.

All living things are

grouped into three

domain:

Eukaryotes

Prokaryotes

and Archaea.

In all cells, DNA does not exist free in solution but rather as a protein-coated complex called chromatin

:// . . / / / / .http www sumanasinc com webcontent animations content organelles html

Eukaryotic Cell Eukaryotes are generally more advanced than

prokaryotes.

Eukaryotic cells are found in animals; plants; fungi and protists cell.

Cell with a true nucleus, where the genetic material is surrounded by a membrane

Eukaryotic genome is more complex than that of prokaryotes and distributed among multiple chromosomes.

Eukaryotic DNA is linear.

Eukaryotic DNA is complexed with proteins called histones.

Numerous membrane-bound organelles.

Complex internal structure.

Cell division by mitosis.

Prokaryotic Cell Prokaryotic Cell Unicellular organisms, found in all

environments. These include bacteria and archaea.

Without a nucleus.

no nuclear membrane (genetic material dispersed throughout cytoplasm

No membrane-bound organelles

Cell contains only one circular DNA molecule contained in the cytoplasm

DNA is naked (no histone)

Simple internal structure.

Cell division by simple binary fission.

Archaea are prokaryotes; organisms without nucleus but some aspect of their molecular biology are more similar to those of eukaryotes.

Timeline Events of Molecular Biology:

• 1860 Mendel – Mendel’s law of inheritance, gene& chromosome

• 1868 Miescher – nuclein, contained an acidic material

• 1890 Weismann - substance in the cell nuclei controls development.

• 1900 Chromosomes shown to contain hereditary information, later shown to be composed of protein & nucleic acids.

• 1928 Griffith’s Transformation Experiment

• 1944 Avery’s Transformation Experiment

• 1953 Hershey-Chase Bacteriophage Experiment

• 1953 Watson & Crick propose double-helix model of DNA

• 1956 Gierer & Schramm/Fraenkel-Conrat & SingerDemonstrate RNA is viral genetic material.

The law of independent assortment

The law of independent segregation

The law of dominance

1 -Mendel’s Three Law of Inheritance:// . . / / /http www sumanasinc com webcontent animations c

/ / .ontent mendel mendel html

Comment: Genes are located on chromosomes

Called in nuclein since it was from the nucleus

Had large amounts of phosphorous and no sulfur so was very different than protein

2 -Friedrick Miescher, a Swiss chemist

(Discovery of Deoxyribonucleic acid)

Comment: the two constituents of chromosomes; Proteins & DNA

Analytical Tests forC, H,P,O and N

“Nuclein”