Molecular Genetics

 Important Molecular Geneticists 1. Meischer-first to discover and isolate DNA from cells; called it nuclein (it was later renamed DNA) 2. Hershey and Chase-first to determine that DNA is the molecule that contains hereditary information 3. Watson and Crick-discovered that DNA has a double helix structure; won a Nobel Prize

4. Wilkins and Franklin-used x-ray crystallography experiments to help determine the structure of DNA along with Watson and Crick; Wilkins shared in the Nobel Prize; Franklin was given no credit because she died of cancer before the Nobel Prize was awarded

 DNA (deoxyribonucleic acid) Is the molecule that stores hereditary (genetic) information Provides the instructions for making proteins Has a double helix structure Is made of 2 chains of nucleotides DNA Nucleotides have 3 parts: 1. Deoxyribose Sugar 2. Phosphate Group 3. Nitrogenous Base

DNA’s Nitrogenous Bases  Adenine (a purine base)  Guanine (a purine base)  Thymine (a pyrimidine base)  Cytosine (a pyrimidine base) DNA’s Base Pairing Rules  Adenine bonds with Thymine (A with T)  Guanine bonds with Cytosine (G with C)

The sugar from one nucleotide is attached to the phosphate group of the nucleotide below it with a covalent bond Nitrogenous base pairs are attached to each other by hydrogen bonds

 RNA (ribonucleic acid) Is a molecule that is involved in protein synthesis RNA Nucleotides have 3 parts: 1. Ribose Sugar 2. Phosphate Group 3. Nitrogenous Base

RNA’s Nitrogenous Bases  Adenine (a purine base)  Guanine (a purine base)  Uracil (a pyrimidine base) *****  Cytosine (a pyrimidine base)

3 Types of RNA 1. Messenger RNA (mRNA)-carries instructions for making proteins from DNA in the nucleus to the ribosomes; structure is a single straight chain of nucleotides; codons are sequences of 3 mRNA nucleotides 2. Transfer RNA (tRNA)-carries amino acids from the cytoplasm to the ribosomes; structure is a single chain of nucleotides folded into a hairpin/cloverleaf shape; anti-codons are sequences of 3 tRNA nucleotides that are complementary to mRNA codons 3. Ribosomal RNA (rRNA)-makes up the structure of the ribosomes; has a globular structure