DNA STRUCTURELS: Molecular

Deoxyribonucleic AcidDeoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses.

Deoxyribonucleic AcidSometimes DNA is compared to blueprints or a recipe, since it contains the instructions needed to construct the parts of a cell.

Deoxyribonucleic AcidDNA encodes our genes.Genes make proteins.Proteins make us what we are.

DNA Organization

Within cells, DNA is packaged in the form of chromatin; DNA is wrapped around proteins called histones (compact and organized).

Chromosome

Supercoils

Coils

Nucleosome

Histones

DNA

double

helix

Discovering DNAThomas Hunt Morgan, working with Drosophila, discovered that phenotypes are associated with chromosomes.

White-eyed males have a specific X chromosome.

Conclusion: Genes are on chromosomes. Is it DNA or Protein?

1908

Transforming PrincipleAvery, McCarty, & MacLeod

-Purified both DNA & proteins separately from Streptococcus pneumonia bacteria.

-Inserted protein into bacteria- no effect

-Inserted DNA into bacteria- transformed harmless bacteria into virulent bacteria

Oswald Avery Maclyn McCarty Colin MacLeod

1944

Blender Experiment

Double HelixWatson and Crick discovered the structure of DNA in 1953.

1953

Nucleotides

DNA is a polymer of nucleotides. Nucleotides are composed of a sugar, a phosphate, and a base.

Hydrogenbonds

Nucleotide

Sugar-phosphatebackbone

KeyAdenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Complementary BasesDNA bases are complementary; meaning...

Adenine always pairs with Thymine Cytosine always pairs with Guanine

Purines & Pyrimidines• A purine is a larger two

ring structure (purine ring paired to an imidazole ring.

• A pyrimidine is a smaller single ring structure.

Imidazole

Hydrogen Bonding

Complementary bases are held together by hydrogen bonds.

Deoxyribonucleic Acid

DNA is a code; the sequence of bases determines the genetic information.

Antiparallel StrandsThe two strands are anti-parallel, running in opposite directions.

DNA can only be read by the cells in one direction (5’-3’).

Genetic InformationEach molecule of DNA is composed of two strands. The sense strand contains the genetic information. The antisense strand is a complementary strand that is used as a template.

Generally only one strand of your DNA is used to make proteins.

DNA