DNA Replication and Protein Synthesis

Biology B-Day 1/3/18 Bellringer What are the 3 parts of a nucleotide? What is the base-pair rule? Agenda Bellringer RNA and Protein Synthesis Notes Transcription and Translation Practice

Biology B-Day 1/3/18 Bellringer What are the 3 parts of a nucleotide? Sugar, Phosphate, Nitrogen Base What is the base-pair rule? A-T and C-G Agenda Bellringer RNA and Protein Synthesis Notes Transcription and Translation Practice

I. DNA – Deoxyribonucleic Acid Genetic Code – Way that cells store info (in nucleus) to be passed to the next generation.

II. DNA Structure DNA is a macromolecule made up of nucleotides. Each nucleotide molecule has 3 subunits: Phosphate Group 5-carbon sugar Nitrogen base

Four Possible Nitrogen Bases: Adenine Guanine Thymine Cytosine A & G: purines T & C: pyrimidines

Nucleotides are joined to form DNA molecules. NOTE: The sugars and phosphates make up the backbone of DNA. (“siderails” of a ladder)

Chargaff Discovered “Base Pairing Rules.” Adenine always pairs with Thymine (2 H bonds) Cytosine and Guanine always pair (3 H bonds) ALWAYS pyrimidine + purine

DNA RECAP: DNA is located in the nucleus The proteins DNA codes for must be made by ribosomes outside the nucleus Therefore, a messenger is sent outside the nucleus to carry the code to the ribosomes.

3 Types of RNA Messenger RNA (mRNA) – made when DNA is transcribed into RNA Transfer RNA (tRNA) – reads the mRNA during translation, translates it into amino acids. Ribosomal RNA (rRNA) – RNA found in ribosomes

Structure of RNA RNA molecules are chains of nucleotides. RNA vs. DNA Sugar in RNA is ribose, DNA is deoxyribose. It is single-stranded. 4 Nitrogen bases are: Adenine Guanine Cytosine Uracil replaces Thymine

Gene expression: turning genes into specific traits, done by RNA. IV. Introduction to RNA Gene expression: turning genes into specific traits, done by RNA. 1st step: copy part of the DNA sequence into RNA (Ribonucleic Acid).  TRANSCRIPTION

2nd: information in RNA is used to make a specific protein  TRANSLATION

NOTE! All base-pair rules are followed: C = G A = U, since T is gone

Transcription: RNA Synthesis Copies DNA into mRNA The RNA molecule will be COMPLEMENTARY to the DNA molecule, NOT identical –b/c it is in “RNA” language. Carried out by RNA polymerase

Steps of Trans. 1. DNA “unzips”. Enzyme: DNA helicase 2. One strand is used as a pattern, or template, for RNA nucleotides. 3. mRNA nucleotides attach to one strand of DNA. Enzyme: Polymerase 4. Newly formed mRNA strand “peels” off and leaves nucleus. 5. DNA molecule “zips” back together

Only certain sections of the DNA code are transcribed into RNA These sections are called genes. Only about 1.5% of DNA is transcribed

Transcription Practice! DNA = A-T-C-T-G-T-T-A RNA = ?

Translation – Process of using the info in mRNA to put together amino acids and make proteins. - Occurs in a series of steps, involves, 3 kinds of RNA, and results in a polypeptide.

In Translation: mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm Every 3 letters, or bases, equals one codon Each codon codes for one amino acid (building block of protein)

II. Nature of the Genetic Code Genes are “directions” that help make proteins (made up of a.a.) Each combination of 3 nucleotides on a strand of mRNA is called a CODON, or 3-letter code word.

Ex. C-U-G, A-C-U are both codons. DNA and mRNA contain information as a sequence of nucleotides The “words” of this language are all 3 nucleotide sequences called codons

Translation Continued: 4. Some codons code for instructions, like STOP. 5. tRNA picks up the correct amino acid in the cytoplasm. 6. Amino Acids attach to anticodons (reverse of codons) on tRNA. 7. tRNA brings the correct amino acid to the ribosome to be added to a growing chain that will become a protein.

Protein Synthesis Protein synthesis is the forming of proteins according to the DNA code Proteins determine traits Central dogma: DNA  RNA  Proteins

Mutations: What are mutations? Mistakes or changes in DNA code One single change in a base, or letter can completely change the meaning of the code. Example: Sickle cell anemia results from a one-letter difference (point mutation) in the code for the red blood cell shape.

Mutations Continued: Germ cell/sex cell mutations: May not show up in the parent, but can be passed onto offspring Sperm or egg cells Somatic Mutations: Where do they occur? In all other cells except germ cells Cannot be passed to offspring.

Mutagens: Substances that cause alteration by a cell, such as UV light, x-rays, smoking, some drugs and other chemicals. Most mutations are harmful, a few are beneficial and many are neutral. Changes in the genetic code can lead to changes in the entire population of species. To what can this lead? Cancer