Chapter 12 – DNA and Proteins DNA Structure: DNA is made of many smaller subunits called nucleotides.

A nucleotide has 3 parts: 1.A sugar (a 5 Carbon deoxyribose) 2.A Phosphate group 3.A nitrogenous base - 4 types of these Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Always pair up Adenine and Guanine are purines (bigger) Cytosine and Thymine are pyrimidines (smaller)

These subunits are arranged in a twisted ladder called a double helix. If you untwisted the ladder, it would look like this: nitrogen base phosphate Sugar weak hydrogen bonds hold the bases together

The sequence (or order) of the bases in all organisms’ DNA is what makes them different from each other. A gene is a segment of DNA that codes for a specific trait.

Stop for DNA structure activity: Be careful with these….they are borrowed from Mr. Pontzer! Please return them exactly as you found them! Thank you! Build a double helix using the drawing you made in your notes. Look at the example up front to see how it goes together. Key is on the next page:

Tubes:Other pieces: Red = AdenineSugar = black Blue = ThyminePhosphate = red Green = Guanine Gray = Cytosine White, round pieces areYellow tubes are the hydogen bondsthe phosphate/sugar bonds. (correct bases must pair!) Longest and longer green tubes are to make a stand for the DNA molecule.

Protein Synthesis Remember! - Proteins have specific shapes for specific functions - Proteins are made from long chains of 20 types of amino acids DNA tells our cells how to put proteins together. - Different proteins exist because amino acids are assembled in different sequences.

Steps of protein synthesis: 1.Transcription – In the nucleus, the DNA code is “copied” onto a molecule of messenger RNA (mRNA) by matching up base pairs. RNA contains uracil (U) instead of thymine(T). After transcription, the mRNA leaves the nucleus and moves to the ribosome.

2. Translation – The ribosome reads the mRNA in 3-base sequences called codons. Specific amino acids are added to a growing protein chain. They are matched up with an anticodon found on a transfer RNA (tRNA) molecule.

What is a mutation? Any change in DNA Any abnormal change in genetic material. Some can be inherited by the next generation if they are present in sex cells.

What causes a mutation? 1.) Changes in the environment OR mutagens a. ultraviolet radiation b. pollutants and chemicals c. tar from tobacco 2.) Errors during replication, transcription, or translation

Types of mutations: Point mutations small (but significant) changes, often in a single nucleotide base. Example: Sickle Cell Anemia is caused by a point mutation.

Point Mutation

Types of mutations: Frame Shift when either insertion or deletion of one or two nucleotide bases. When this occurs, the “reading frame” is changed so that all the codons read after the mutation are incorrect.

Disorders that result from mutations: Sickle Cell Anemia PKU Cystic Fibrosis

End Result: Different polypeptide or protein chains can be made from different amino acid sequences. These proteins will have different functions! Chromosomal Mutations