MOLECULAR GENETICS

● what is DNA?● 23 and me ☺

History (1):The transforming principle

History (2):Hershey & Chase Experiment

Central Dogma of Molecular Biology

DNA → RNA → protein

1) DNA contains all the genetic information about an organism.

2) Regions on DNA that code for specific attributes are called genes.

3) In order for the information within a gene to be useful, it has to be translated into proteins.

The end proteins determine individual traits!

What makes good genetic material?

● Stable source of information

● Ability to replicate accurately

● Capable of change

DNA

-DNA Stands for DeoxyriboNucleic Acid

-DNA is the hereditary material inherited from past generations

-The vast majority ( >99%) of your DNA is in the nucleus of your cells

DNA Structure-double helix.

- sugar-phosphate backbone with nitrogenous groups attached

-monomers that make up nucleic acid

Three components

1. Pentose sugarDNA = deoxyribose

2. Nitrogenous base

3. Phosphate group attached to 5’ carbon

Nucleotides

Four bases:

Adenine and guanine are known as purines

Cytosine and thymine are known as pyrimidines

-Nucleotides are linked by phosphodiester bonds

Phosphodiester bond

- covalent bond between the phosphate group (attached to 5’ carbon) of one nucleotide and the 3’ carbon of the sugar of another nucleotide.

-very strong: DNA is remarkably stable- can be boiled without degrading!

● The DNA helix is composed of two ANTIPARALLEL strands

5’: phosphate3’: OH of sugar

5’ and 3’● the ends of the DNA chain are not the

same● One end of the chain has a 5’ carbon

(bound to phosphate group) and the other end has a 3’ carbon (bound to OH group)

- New nucleotides are added only at the 3’ end: 5’ → 3’ extension

5’ end

3’ end

COMPLEMENTARY BASE PAIRING● Polynucleotide chains join together

through hydrogen bonding◦ A forms 2 hydrogen bonds with T

◦ C forms 3 hydrogen bonds with G