Homework questions to be emailed to  valenciabiologyhw@gmail.com

1. List the 3 components of a nucleotide
2. Distinguish between ribose and deoxyribose
3. Distinguish between the leading strand and the lagging strand
4. Explain how DNA differs from RNA
5. Explain how information flows from gene to protein

DNA Notes
Life’s Operating Instructions
In 1953, James Watson and Francis Crick shook the world
With an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA

Maurice Wilkins and Rosalind Franklin
Were using a technique called X-ray crystallography to study molecular structure
Rosalind Franklin
Produced a picture of the DNA molecule using this technique

Watson and Crick deduced that DNA was a double helix
Through observations of the X-ray crystallographic images of DNA

Franklin had concluded that DNA
Was composed of two antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule’s interior
The nitrogenous bases
Are paired in specific combinations: adenine with thymine, and cytosine with guanine

A eukaryotic chromosome
May have hundreds or even thousands of replication origins

A summary of DNA replication
Replicating the Ends of DNA Molecules
The ends of eukaryotic chromosomal DNA
Get shorter with each round of replication

During transcription
The gene determines the sequence of bases along the length of an mRNA molecule

Cracking the Code
A codon in messenger RNA
Is either translated into an amino acid or serves as a translational stop signal

The ribosome has three binding sites for tRNA
The P site
The A site
The E site

Building a Polypeptide
We can divide translation into three stages
Initiation
Elongation
Termination

Ribosome Association and Initiation of Translation
The initiation stage of translation
Brings together mRNA, tRNA bearing the first amino acid of the polypeptide, and two subunits of a ribosome

Elongation of the Polypeptide Chain
In the elongation stage of translation
Amino acids are added one by one to the preceding amino acid

Termination of Translation
The final stage of translation is termination
When the ribosome reaches a stop codon in the mRNA