DNA DEOXY - RIBO - NUCLEIC ACID

DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: 1. Phosphate group 2. Pentose sugar 3. Nitrogenous base

Nucleotides Phosphate Deoxyribos e Sugar Nitrogenous Base

Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

Nucleotides A Adenine T Thymine G Guanine C Cytosine

Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

DNA Structure Because of this complementary base pairing, the order of the bases on one side of the DNA molecule/“ladder” determines the order of the bases in the other, opposite side of the ladder.

G G A T T A A C T G C A T C One side of the DNA moleculeOpposite side of the DNA molecule The complimentary Nitrogen bases fit together Like puzzle pieces.

DNA Structure To crack the genetic code found in DNA we need to look at the sequence of bases. The bases are arranged in triplets called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C

Each gene has a unique sequence of nitrogen bases. These gene sequences are specific instructions for making proteins and proteins are VERY important building blocks of organisms. It is these proteins and combinations of proteins that build cells & tissues or work as enzymes (chemical communicators) in organisms. Proteins are made of many chains of amino acids.

The gene determines the order of the amino acids in the protein. A change in the amino acid order results in a different protein. Different proteins create different tissues or give instructions for different traits in organisms.

Protein DNA Gene Trait

DNA Structure Video - 1:19

Steps to Copying DNA: During the S1 Phase of Interphase… 1. Enzymes act to separate the sides of the DNA at the bond between the nitrogen bases. (like a zipper unzipping) 2. Nucleotides, floating freely around the molecule, then attach themselves like magnets at the nitrogen base bonding sights of both halves of the molecule. 3. When all open nitrogen base bonding sites are full, a new, complete, HOPEFULLY identical DNA molecule is formed. There now are two. Both are copies of each other. 4. The cell is now ready to undergo division cell. * Occasionally the DNA replication process doesn’t go perfectly and that can lead to problems called Mutations. We will discuss this later.

* Genes are found in the nucleus of cells. * Proteins are synthesized in the ribosomes in the cells. * The instructions in the genes, for constructing the proteins, is carried from the nucleus to the ribosomes of the cell by another type of nucleic acid, known as ribonucleic acid or RNA

* RNA molecules are similar to DNA. Instead of the sugar Deoxribose, RNA has the sugar molecule Ribose. And, instead of the nitrogen base Thymine (T), it contains the nitrogen base Uracil (U). * Three main types of RNA are: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)