DNA DNA is often called the blueprint of
DNA • DNA is often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell.
Why do we study DNA? DNA We study DNA for many reasons, e. g. , • its central importance to all life on Earth, • medical benefits such as cures for diseases, • better food crops.
DNA Fun Facts by the Numbers • Each cell has about 2 m of DNA. • The average human has 75 trillion cells. • The average human has enough DNA to go from the earth to the sun more than 400 times. The earth is 150 billion m or 93 million miles from • DNA has a diameter of the sun. only 0. 00002 m.
DNA double helix DN A (Deoxyribonucleic Acid) is the substance that makes up the genes and chromosomes of all living things.
DNA Double Helix 1. Two strands of nucleotides wound about each other in a twisting shape. 2. Sugar – phosphate backbones on the outside of the double helix and the nitrogen bases are on the inside.
DNA Double Helix Models
Building block of DNA is the nucleotide. A nucleotide consists of a sugar, phosphate and nitrogen base.
DNA Structure • 1. The sugar in DNA is deoxyribose. • 2. DNA contains four different nitrogenous bases. Thymine and cytosine have single-ring structures (pyrimidines). • 3. Adenine and guanine have doublering structures (purines)
Nitrogen Bases of DNA
Chargaff’s Rule: 1. Adenine and Thymine always join together A T 2. Cytosine and Guanine always join together C G
• The purine bases are adenine and guanine. • (LARGE and in charge) • The pyrimidine bases are cytosine and thymine. (U is for uracil found in RNA) • (CUT a piece of pie).
The nitrogen bases of DNA A=T G=C
DNA structure
Replication - DNA is copied • 1 st step - two chains separate at replication fork • 2 nd step - helicase enzymes break hydrogen bonds between base pairs • 3 rd step - DNA polymerase binds new nucleotides to existing chains -G -A -C -T -A -G -C-T-G-A-T-C- -G-C-A-T-C-G-T-A-A-T-G-C- -G-A-C-T-A-G- CTGATC-
- Slides: 17