DNA-notes

A. First Discoveries Griffith- experiment showed that live uncoated bacteria acquired the ability to make coats from dead coated bacteria. He called the process transformation.

Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Go to Section:

2. Avery- discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation to the next. 3. Hershey & Chase- used radioactive labeling to identify DNA. They showed that DNA, not protein, is the genetic material of a bacteriophage (virus).

Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:

Erwin Chargaff discovered: Chargaff’s Rule Erwin Chargaff discovered: a. A (adenine) always equals (joins) to T (thymine) b. G (guanine) always equals (joins) to C (cytosine)

4. Rosalind Franklin Used a technique called X-ray diffraction to determine DNA was helical.

5. Watson and Crick Built a 3 dimensional model of a DNA molecule which was called a double helix

6. DNA is tightly coiled around a protein called histones 6. DNA is tightly coiled around a protein called histones. The coil then forms your chromatin. Coiled chromatin forms your chromosomes.

DNA Replication-see how it works

DNA Replication

DNA Replication

DNA Replication

DNA Replication 1. Before a cell divides, DNA is copied (replicated). 2. During DNA replication, the DNA molecule separates into 2 strands. Each new strand will hook up with it’s complementary base partner, making 2 new complementary strands. The strands follow Chargaff’s rule on base pairing. 3. The sites where separation and replication occur are called replication forks. 4. The replication is carried out by enzymes that “unzip” the DNA called helicase.

Figure 12–11 DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand Go to Section:

DNA

Complementary base pairs form new strands. DNA Replication Complementary base pairs form new strands.

DNA

RNA Structure A. RNA Structure 1. Nucleic Acid made of single chains of nucleotides 2. The sugar is called Ribose. 3. Base pairs are cytosine & guanine, adenine & uracil. 4. Uracil replaces the thymine.

Strands of nucleotides Compare DNA to RNA Structure: DNA RNA Strands of nucleotides Double Single Sugars Deoxyribose Ribose Nitrogen bases A, T, C, G A, U, C, G

B. Types of RNA 1. Messenger RNA (mRNA)- carries the instructions to make a particular protein from DNA 2. Ribosomal RNA (rRNA)- makes up the major part of ribososmes 3. Transfer RNA (tRNA)- transfers the amino acids to ribosomes during protein synthesis

Transcription A. The process of producing mRNA from DNA. 1. RNA polymerase binds to the DNA and separates the strands. 2. RNA polymerase uses one strand of DNA as a template to form a strand of mRNA. 3. RNA polymerase enzymes will only bind to regions of DNA called promoters (it has a specific base sequence).

Transcription RNA polymerase DNA RNA Go to Section: Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA Go to Section:

B. RNA Editing Intron- intervening sequences that are removed from the mRNA molecules before they become functional. 2. Exons- the remaining portions that are spliced back together to form the final mRNA.

Genetic Code Three bases are called codons (Ex. GCA) B. Proteins are made of long chains called polypeptides. Codons specify a single amino acid that is to be added to the polypeptide Polypeptides are made by joining the amino acids.

Figure 12–17 The Genetic Code Go to Section:

Translation (Protein synthesis) A. The decoding of an mRNA message into a protein. B. Takes place in/on the ribosomes. Steps involved: 1. mRNA is transcribed from DNA and released in the cytoplasm 2. Translation begins when mRNA attaches to a ribosome in the cytoplasm at the start codon (AUG) 3. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA. This has an amino acid attached to one end.

The ribosome positions the start codon to attract its anticodon, which is part of tRNA and binds them together. Once the first and second codon and anticodon are bound, the ribosome joins the two amino acids and the tRNA breaks away. Chains of amino acids continue to grow until the ribosome reaches a stop codon on the mRNA strand. Then it replaces the chain.

Figure 12–18 Translation Section 12-3 mRNA Go to Section: Nucleus Messenger RNA Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon Go to Section:

Figure 12–18 Translation (continued) Section 12-3 The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome Go to Section:

Concept Map Section 12-3 Go to Section: RNA can be Messenger RNA also called which functions to also called which functions to also called which functions to Carry instructions rRNA Combine with proteins tRNA from to to make up Ribosome Go to Section: