Chapter 4: DNA – The Code of Life Lesson 1: The Genetic Code Cells and Heredity Chapter 4: DNA – The Code of Life Lesson 1: The Genetic Code

The Structure of DNA Ladder structure called a “double-helix”. The sides are made of sugar molecules called deoxyribose and phosphate molecules. The rungs are made of nitrogen bases (nucleotides), which contain nitrogen and other elements.

DNA and the Genetic Code There are four nucleotides: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Adenine always pairs with thymine (AT or TA) Cytosine always pairs with guanine (CG or GC) “all tigers can growl”

The Connection A gene is a section of your DNA. It is made up of several nucleotides in a row. The order that these nucleotides are organized determines the type of protein that will be made.

The Connection It is the order of these bases that forms the code for proteins. The genetic code is a triplet code: 3 nucleotide bases codes for 1 amino acid (protein). Some amino acids have one code, while others have 2, 3, or 4.

DNA Replication The process in which an identical copy of a DNA strand is made for a new cell. The strands “unzip” between the nucleotides, forming two strands with an open side. The matching nucleotides (A-T; C-G) join the bases and form a complete strand of DNA.

Chapter 4: DNA – The Code of Life Lesson 2: How Cells Makes Proteins Cells and Heredity Chapter 4: DNA – The Code of Life Lesson 2: How Cells Makes Proteins

Protein Synthesis Protein synthesis is the production of proteins in a cell. Cells use the information from genes/chromosomes to produce specific proteins. Takes place in the cytoplasm.

Protein Structure There are 20 amino acids, but they can combine in different ways to make thousands of proteins.

RNA RNA stands for ribonucleic acid. RNA only has one strand, and instead of having thymine it has uracil (U). Messenger RNA (mRNA): copies the message from DNA in the nucleus and brings it to the ribosomes in the cytoplasm. Transfer RNA (tRNA): carries amino acids to the ribosome and adds them to the protein.

Protein Synthesis A strand of DNA unzips, and a strand of RNA is made in a similar way of DNA replication. C-G still pair together, T pairs with A, but A pairs with Uracil. (C-G, G-C, T-A, A-U) When the strand is made, the mRNA leaves the nucleus and goes to a ribosome.

Protein Synthesis The ribosome attaches to the strand, and the triplet code is provided. tRNA attaches to mRNA based on the codes. As amino acids are produced by the codes/ribosomes, they are linked together to form a protein. There are “stop” triplet codes that tell the RNA when protein synthesis is complete.

Chapter 4: DNA – The Code of Life Lesson 3: Mutations Cells and Heredity Chapter 4: DNA – The Code of Life Lesson 3: Mutations

What is a Mutation? Mutation: any change in the DNA of a gene or chromosome. They can cause a cell to produce the wrong proteins, which can change an organism’s traits. Mutations in autosomal cells do not pass on; mutations in gametes can be passed on.

Types of Mutations Base pairs can be added/deleted or read wrong in the DNA, or there can be too many or too little chromosomes in the DNA. They can be harmful, helpful, or neither. If the mutation does not increase an organism’s likelihood of survival, it is harmful.

Cancer A disease in which cells grow and divide uncontrollably. Some people are more likely to have cancer due to their inherited traits. Other factors, such as smoking and exposure to UV rays, can also increase someone’s chances of getting cancer.

Cancer Cancer is thought to begin when a mutation changes the cell cycle, and causes cells to divide abnormally. Grows too big and/or divides too often. When several abnormal cells are together, they form a tumor. Sometimes, cancerous cells break away from a tumor and travel through the bloodstream to other areas of the body.

Cancer Surgery, radiation, and drug therapy can destroy cancer cells. Radiation uses high energy waves to kill the cancer cells. However, this could cause some damage to normal cells. Chemotherapy is the use of drugs to treat cancer. The drugs travel through the bloodstream, and like radiation, can cause damage to normal cells as well.