DNA and DNA Replication

Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.

DNA is a long molecule made up of units called nucleotides

Nucleotides are made up of 3 basic components: (1) a 5-carbon sugar (2) A phosphate group (3) a nitrogenous group

There are 4 kinds of nitrogenous bases in DNA

1) Adenine

2) Guanine

3) Cytosine

4) Thymine

Rosalind Franklin was able to take X-Rays beams on DNA to find a distinct pattern

James Watson and Francis Crick took these results and were able to build a structural model of DNA

This model of DNA was a Double Helix, in which two strands were wound around each other

Prokaryotic Cells lack nuclei and many of the organelles found in Eukaryotes (HUMAN cells are Eukaryotic )

Eukaryotic DNA is more complicated then Prokaryotic Cells and is LOCATED in the cell nucleus in the form of a number of chromosomes

***Human cells have 46 Chromosomes

Eukaryotic chromosomes contain both DNA and protein tightly packed together to form a substance called chromatin

Chromatin consists of DNA that is tightly coiled around proteins called histones

Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing

If you could separate the two strands, the rules of base pairing would allow you to reconstruct the base sequence of the other strand.

DNA replication occurs in hundreds of places

During DNA replication, the DNA molecule produces two new complementary strands. Each strand of the double helix serves as a template for the new strand

Before a cell divides, it duplicates its DNA in a copying process called replication

DNA Replication is carried out by a series of enzymes

These enzymes "unzip" a molecule of DNA

The unzipping occurs when the hydrogen bonds between the base pairs are broken and the two strands of the molecule unwind.

The principal enzyme involved in DNA replication is called DNA polymerase

DNA polymerase also "proofreads" each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNA