DNA
What is DNA? A code in the cell that contains the hereditary material The code is a chemical called deoxyribonucleic acid Every cell in your body contains DNA
DNA Structure Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form by using an X-ray Similar to twisted ladder James Watson & Francis Crick made a model of DNA molecule
A DNA Model Each side of the ladder is made of sugar-phosphate molecule Called the “backbone” Sugar = deoxyribose
Rungs of the ladder are made up of nitrogenous bases There are four types of bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)
Base Pairing Adenine always pairs with Thymine A-T Cytosine always pairs with Guanine C-G
Copying DNA The two sides of DNA unwind and separate Each side becomes a pattern for a new DNA strand
Genes DNA in your cells stores the instructions for making proteins Each chromosome contains hundreds or thousands of genes
Making Proteins Genes are found in the nucleus, but proteins are made on ribosomes in the cytoplasm The code for making proteins are carried from the nucleus by RNA or Ribonucleic Acid
Ribonucleic Acid U = Uracil RNA is different from DNA RNA is not a spiral, but one single strand RNA has the bases A, G, C, and U not T U = Uracil Sugar is ribose, not deoxyribose
DNA VS. RNA DNA RNA STRUCTURE SUGAR BASES Double Helix Single Strand Deoxyribose Ribose BASES A, T, C, G A, U, C, G
Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
Controlling Genes Each cell only uses some of the thousands of genes to make proteins Cells must be able to control genes by turning some genes on and others off
Mutations Permanent changes in the DNA sequence of a gene These happen when the DNA is not copied correctly They cause incorrect proteins to be made
Causes of Mutations X-rays Sunlight Some chemicals
Results of Mutations Some mutations are beneficial They add variety to the species Many mutations are harmful and can cause death Cystic Fibrosis Some mutations have no effect on the organism