Molecular Genetics Molecular biology is the branch of

Molecular Genetics

• Molecular biology is the branch of biology that study gene structure and function at the molecular level. • The Molecular biology is the field overlaps with other areas, particularly genetics and biochemistry.

Histor y ‘‘DNA is the genetic material’’ u T. H. Morgan (1908) § u Frederick Griffith (1928) § u confirmation that DNA is genetic material Watson & Crick (1953) § u transforming factor is DNA Hershey & Chase (1952) § u a transforming factor can change phenotype Avery, Mc. Carty & Mac. Leod (1944) § u genes are on chromosomes determined double helix structure of DNA Meselson & Stahl (1958) § semi-conservative replication

• • Eukaryotic cells are found in animals, plants, fungi and protists cell; Cell with a 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 complexed with proteins called histones; Numerous membrane-bound organelles; Cell division by mitosis. Eukaryotes are generally more advanced than prokaryotes

Flow of genetic information in a cell. transcription DNA translation RNA protein

Mutations are changes in the genetic material of a cell n n Large scale mutations: chromosomal; always cause disorders or death u nondisjunction, translocation, inversions, duplications, large deletions Point mutations: alter 1 base pair of a gene 1. Base-pair substitutions – replace 1 with another Missense: different amino acid Nonsense: stop codon, not amino acid 2. Frameshift – m. RNA read incorrectly; nonfunctional proteins Caused by insertions or deletions

The Genome n n Totality of genetic information of an organism. Encoded in the DNA.

Species and Number of Chromosomes Species Human Mouse Rat Fruit flies Bacteria Number of chromosomes 46 40 42 8 1

Human Genome; Arranged on multiple chromosomes; twenty three pairs of chromosomes; n Twenty two pairs (autosomes). n One pair (sex chromosome) (xx) (female) or (xy) (male). Humans have 23 pairs of chromosome in every cell (except mature red blood cells. . ); Gametes or sex cells (sperm and eggs) have half the normal complement of chromosomes.

General Structure of Nucleic Acid DNA and RNA are long chain polymers of small chemical compound called nucleotides.

Nucleotides; ring shaped structures composed of: § Nitrogenous base; these bases are classified based on their chemical structures into two groups: Purine: double ringed structure (Adenine and Guanine). Pyrimidine: single ring structures (cytosine and thymine). § Sugar § Phosphate group

Nucleotides n DNA: Four different types of nucleotides differ in nitrogenous base: n A is for adenine; n G is for guanine; n C is for cytosine and n T is for thymine. n. RNA: thymine base replaced by uracil base.

Nucleotides

§ Deoxyribonucleic Acid (DNA) is the The DNA genetic material of all cellular organisms and most viruses. § DNA; the gigantic molecule which is used to encode genetic information for all life on Earth. § DNA responsible for preserving, copying and transmitting information within cells and from generation to generation.

Molecular Cloning or Recombinant DNA Technology: To clone means to make identical copies. DNA cloning involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copy of the selected gene. When cloned under an appropriate expression vector, a gene can be expressed (transcribed and translated), at desired level to produce recombinant proteins. This technology has made it possible to isolate, clone and produce DNA for all the genes in appropriate quantity so that they can be sequenced and characterized. Similarly, some of the genes which are expressed at very low level, can be cloned and desired amount of recombinant proteins can be produced.

Proteins made in animals Use recombinant DNA technology to express a human protein in the mammary glands of a cow, sheep, goat, (rabbits and hamsters used in early experiments) then patients drink the milk from these transgenic animals. • Blood-clotting factors for hemophiliacs • Collagen • Antibodies (vaccines)

BIOTECHNICALLY SIGNIFICANT PROTEINS n n A wide variety of proteins find industrial application. These include enzymes, antibodies, hormones, blood factors, growth factors and regulatory factors. Such proteins are employed as therapeutic and diagnostic agents.