Introduction to Studying DNA

DNA Structure and Function Most Biotechnology Industries’ R&D is centered around two basic concepts: The manipulation of DNA molecules within all cells (manipulation of genes). DNA’s role in the coding of proteins. (Proteins do all the work of the cells and give cells and organisms their unique characteristics.)

Central Dogma of Biology The basis of all biotechnology. Connects the genetic code to protein production. (gene: a section of DNA on a chromosome that contains the genetic code for a specific protein) Over 2000 different proteins synthesized by each cell. Each cell in an organism contains the exact same DNA (genome); however, every cell does not produce the same proteins. The more complex an organism is, the larger that organism’s genome will be.

Central Dogma of Biology In Nucleus In Cytoplasm Replication of the DNA Transcription Production of mRNA, rRNA, or tRNA Translation of the mRNA into protein

Central Dogma of Biology Replication Transcription Translation Tutorial Video

Comparisons of Genomes Organism # of Genes Genome Size (# of bp) H. Influenza (childhood ear infection) 1,749 1,830,137 M. Gentalium (free-living bacteria) 470 580,070 C. Elegans (free-living roundworm) 19,899 97,000,000 E. Coli (intestinal bacteria) 4,377 4,639,221 H. Sapiens (human) 40,000 3,000,000,000

Similarities in DNA Molecules Among All Organisms All DNA molecules are composed of four nucleotide monomers: A C G T Purines (double carbon rings) Pyrimidines (single carbon rings)

Similarities in DNA Molecules Among All Organisms DNA molecules form a double helix Sugar-Phosphate backbone Phosphodiester Bonds hold nucleotide to nucleotide – STRONG BONDS A always bonds to T C always bonds to G Hydrogen Bonds hold base to base; therefore, hold strand 1 to strand 2 – WEAK BONDS

Similarities in DNA Molecules Among All Organisms Purine always bonds to a Pyrimidine Therefore the rungs of the ladder are always the same width: A T = G C

Similarities in DNA Molecules Among All Organisms DNA strands are antiparallel The 5' end of one strand pairs with the 3’ end of the opposite strand. T C G A

Similarities in DNA Molecules Among All Organisms There are 10 base pairs for every complete turn of the helix. Maintains constant shape so enzymes and regulatory proteins can work! 4 3 5 7 8 9 2 6 10 1 1 complete turn of helix

Similarities in DNA Molecules Among All Organisms DNA undergoes semiconservative replication 2 daughter strands produced from a single parent strand. 1 parent strand goes into each daughter cell during cell division.

Similarities in DNA Molecules Among All Organisms: SUMMARY All DNA molecules are composed of four nucleotide monomers (A, T, C, & G). DNA molecules form a double helix. Purine always bonds to a Pyrimidine. (A T & G C) DNA strands are antiparallel. There are 10 base pairs for every complete turn of the helix. DNA undergoes semiconservative replication.

Variations in DNA Molecules Among Organisms The number of DNA strands (chromosomes) varies by organism. The more complex the organism… the more chromosomes that organism has. Humans – 46 total chromosomes in every cell (23 pairs) E. coli – 1 chromosomes + 2 plasmids

Variations in DNA Molecules Among Organisms The length of the DNA strands varies by organism. The more complex the organism… the greater the number of base pairs (bp) that organism has. Human Genome 3,000,000,000 bp E. Coli Genome 4,639,221 bp

Variations in DNA Molecules Among Organisms The number and types of genes varies by organism. The more complex the organism… the greater the number of genes that organism has. Human Genome ~40,000 genes E. Coli Genome 4,377 genes

Variations in DNA Molecules Among Organisms The shape of the DNA strand varies by organism. Eukaryotes…linear chromosomes Prokaryotes...circular chromosomes & plasmids Eukaryotic DNA -- linear Prokaryotic DNA -- circular

Variations in DNA Molecules Among All Organisms: SUMMARY The number of DNA strands varies by organism. (more complex = more chromosomes) The length of the DNA strand varies by organism. (more complex = more base pairs) The number and types of genes varies by organism. (more complex = more genes) The shape of the DNA varies by organism. (eukaryotic = linear DNA; prokaryotic = circular DNA)