Presentation on theme: "DNA & RNA Chapter 12 Page 287. 12-1 DNA All good scientists have questions. How do genes work? What are genes made out of? How do genes determine."— Presentation transcript:
12-1 DNA All good scientists have questions. How do genes work? What are genes made out of? How do genes determine the characteristics of organisms?
Scientists That Led to DNA’s Discovery 1928 Griffith Wanted to learn how bacteria make people sick. He tested mice with a harmless strand of bacteria. They lived! He tested mice with disease causing pneumonia. They died! Was it some sort of poison that the bacteria made that killed the mice?
Griffith Continued He tested his hypothesis to see if the bacteria did secrete a toxic poison. He killed all of the bacteria with heat and injected it into the mice. They lived! Conclusion: It wasn’t a toxin that killed the mice. Next he tried mixing the heat killed bacteria and the harmless bacteria thinking the mice would live. They died! This led to the discovery of transformation. Somehow the harmless bacteria had been transformed into the disease causing bacteria?!?!?!
Griffith’s Hypothesis Some factor was transferred between the dead, disease causing bacteria and the live, harmless bacteria. That factor must have contained information that could change harmless bacteria into harmful ones. The ability to cause disease is inherited so the factor might be a gene!
1944 Avery Repeated Griffith’s work to determine which molecule was require for transformation. Took heat killed bacteria and treaded it with enzymes that destroyed everything but DNA. Transformation still occurred. Repeated the experiment with an enzyme that destroyed DNA. Transformation did not occur.
Conclusion Avery discovered that DNA stores and transmits genetic information from one generation to the next.
DNA Now scientists wondered… How could DNA carry information from one generation to the next? How does DNA put that information to work by giving organisms their characteristics. How is DNA copied every time a cell divides? Hhhhmmmmm……
Structure of DNA DNA is a long molecule made up of nucleotides. A nucleotide is made of three basic components. A sugar called deoxyribose. A phosphate group. A nitrogenous base (1 of 4 types) Adenine (A) a large purine Guanine (G) a large purine Cytosine (C) a small pyrimidine Thymine (T) a small pyrimidine
You make one! Gather 6 different colors of construction paper (one for each element of a DNA molecule). Make 8 nucleotides by cutting, taping and labeling the parts of the molecule. Once all 8 nucleotides are made call over Mrs. Haberman for approval before you proceed with connecting them into a strand of DNA. Turn to page 291 for a pattern to follow.
Chargaff’s Rule He discovered that A=T and G=C in DNA molecules. We call this base pairing. http://www.hhmi.org/biointeractive/dna/DN Ai_chargaff_ratio.html http://www.hhmi.org/biointeractive/dna/DN Ai_chargaff_ratio.html
Add to your model. Now create a corresponding chain of DNA to complement the one you’ve already made. Start by making 8 nucleotides that will base pair A=T and G=C with the ones you’ve already made.
The Double Helix Using Rosalind Franklin’s X-Ray image in the 1950’s, Watson and Crick discovered that DNA is in the shape of a double helix. A double helix is when 2 strands are wrapped around each other. They also discovered that there are 2 hydrogen bonds between A and T and three hydrogen bonds between G and C. http://www.hhmi.org/biointeractive/dna/DNAi_watson_ba sepairing_anim.html http://www.hhmi.org/biointeractive/dna/DNAi_watson_ba sepairing_anim.html Using a line to represent the hydrogen bonds, connect the base pairs on your paper model.
12-2 Chromosome and DNA Replication Where is DNA found? How is it organized? Where are genes?
Where is DNA? Prokaryotes lack a nucleus so the DNA is found in the cytoplasm. Usually a single circular DNA molecule. Eukaryotes have a nucleus that contains the DNA. Can be unwound as chromatin or tightly coiled as chromosomes.
How big is DNA? Very long! See image on page 296. The nucleus of a human cell contains more than 1 meter (3.3 feet) of DNA! http://www.hhmi.org/biointeractive/dna/DN Ai_packaging_vo2.html http://www.hhmi.org/biointeractive/dna/DN Ai_packaging_vo2.html
DNA Extraction Virtual Lab http://learn.genetics.utah.edu/content/labs/ extraction/ http://learn.genetics.utah.edu/content/labs/ extraction/ See and touch real DNA! http://learn.genetics.utah.edu/content/labs/ extraction/howto/
DNA Replication Watson and Crick realized that the double helix structure explained how DNA could be so easily copied or replicated. Each strand of DNA has the necessary information needed to construct another strand by base pairing. The sites where separation and replication occur are called replication forks. http://www.hhmi.org/biointeractive/dna/DNAi_replication_sch ematic.html http://www.hhmi.org/biointeractive/dna/DNAi_replication_sch ematic.html
Duplicating DNA During DNA replication; The DNA molecule separates into 2 strands. Then it produces 2 new complementary strands by base pairing A=T and G=C. Each strand serves as the template for the new strand being created. EXAMPLE: strand TACGTT will make strand ATGCAA Note that each DNA molecule contains one original strand and one new strand! http://www.hhmi.org/biointeractive/dna/DNAi_replic ation_vo1.html http://www.hhmi.org/biointeractive/dna/DNAi_replic ation_vo1.html
Lets Review DNA! What is DNA made of? How is it arranged?
Chapter 12-3 RNA & Protein Gene Coded DNA instructions that control the making of proteins within a cell. http://www.hhmi.org/biointeractive/dna/DNAi_coding_ sequences.html http://www.hhmi.org/biointeractive/dna/DNAi_coding_ sequences.html So how do we decode these messages? The first step in decoding is to copy a sequence of DNA and turn it into RNA. Ribonucleic acid.
The Structure of RNA RNA is made up of a long chain of nucleotides. A ribose sugar A Phosphate And one of 4 bases (A, U, G, C)
DNA and RNA comparisons DNA Deoxyribose sugar Made up of two strands (double stranded). Bases are A, T, G, C The master plan! RNA Ribose sugar Made of one strand (single stranded) Contains the base uracil instead of thymine. A, U, G, C The blue prints!
RNA is… A disposable copy of a segment of DNA. A working copy of a single gene. Responsible for making proteins. Proteins are made by assembling amino acids. Amino acids are the building blocks of proteins.
Types of RNA Messenger RNA mRNA Carries the coded copy of a gene from the DNA inside the nucleus to a ribosome in the cytoplasm. The blueprint of the master copy. Ribosomal RNA rRNA This is where the proteins are put together. The construction site. Transfer RNAtRNA Brings the amino acids to the ribosome. It knows which amino acid to drop of from the coded message on the mRNA. The construction workers that put the building together.
Let’s see what you remember Activity time http://www.indiana.edu/~ensiweb/connections/gen etics/diy.dna.html http://www.indiana.edu/~ensiweb/connections/gen etics/diy.dna.html
DNA base pair practice On a piece of paper I want you to base pair the following DNA sequence. TTAGCATCCGAT _______________
Transcription When a DNA code is turned into a complementary strand of mRNA. Requires an enzyme known as RNA polymerase. RNA polymerase separates the DNA strands where there is a “start” code. http://www.hhmi.org/biointeractive/dna/DNAi_trans cription_vo2.html http://www.hhmi.org/biointeractive/dna/DNAi_trans cription_vo2.html
RNA base pairs Remember that RNA does NOT have a T as a base. So when you transcribe DNA into mRNA it will look like this. Transcription example DNA = ATTAAACGTTGA mRNA = UAAUUUGCAACU
Now you try Transcribe the following DNA strand into mRNA. DNA = ATTGCATGACATCA mRNA = __________________________
Proteins Proteins are made by joining amino acids into long chains called a polypeptide. The type of protein that’s made is determined by the order of the amino acids.
The Genetic Code The “language” of mRNA instructions is called the genetic code. The code is written using 4 letters; A, U, G, C How can a code with only 4 letters carry instructions for 20 amino acids? http://www.hhmi.org/biointeractive/dna/DNAi_triplet_code.html http://www.hhmi.org/biointeractive/dna/DNAi_triplet_code.html
A Codon The genetic code is written 3 letters at a time. Each 3 letter “word” in in mRNA is known as a codon. Each codon (three consecutive nucleotides) specifies a single amino acid. UCGCACGGU is read UCG-CAC-GGU (3 codons) Practice using the code wheel on page 303.
Translation The instructions of mRNA must be “read” and put to use. This happens on a ribosome. Decoding a mRNA message into a protein is called translation. Translation takes place on ribosomes.
Translation example mRNA = CAUGCUUAGUCG Will be read by its codons CAU-GCU-UAG-UCG tRNA anticodons GUA-CGA-AUC-AGC would be
Protein Synthesis Steps pg. 304 First, mRNA is transcribed in the nucleus from our DNA. The mRNA leaves the nucleus to find a ribosome in the cytoplasm. The mRNA moves through the ribosome one codon at a time. A tRNA drops off the amino acid it’s instructed to by base pairing with their anticodons. The three letter code on a tRNA. The polypeptide chain continues to grow until it reaches a stop codon. The completed protein is then released. http://www.hhmi.org/biointeractive/dna/DNAi_translation_vo2.html
Let’s put the story together! Now you will make a protein synthesis story book, song, skit, etc. You make work alone or in a small group for the skit or a team of two for the song. Make your story complete and be sure to tell the whole story. From transcription to translation. You will be graded on creativity, ability to hold the interest of your audience, thoroughness and accuracy.
Protein Synthesis Game Race the cell http://nature.ca/genome/04/041/041_e.cfm http://nature.ca/genome/04/041/041_e.cfm
So what do proteins have to do with me? Everything! Many proteins are enzymes which regulate chemical reactions. A gene that codes for an enzyme to produce pigment can control the color of a flower. Genes for certain proteins regulate the rate and pattern of growth, controlling its size and shape. Proteins are microscopic tools, each specifically designed to build or operate a component of a living cell.
Chapter 12-4 pg. 307 Mutation When a cell makes a mistake copying its DNA, inserting an incorrect base, or skiping a base. Two types, gene and chromosomal.
Gene Mutations (humans have thousands of genes) Point mutations When a base at a single point is changed in a gene. Substitutions (one base is changed to another) Usually only affects a single amino acid. Insertions (an extra based is added) Deletions (a base is left out) Insertions and deletions are much more dramatic!
Gene Mutations con’t Frameshift mutations Insertions and deletions shift the “reading frame” around the codons. This can change EVERY amino acid after the mutation. This can alter a protein so much that its unable to perform its normal function. See page 307 for examples
Chromosomal Mutations Involve changes in the number OR structure of chromosomes. Humans have a total of 46 chromosomes. See page 308 for examples
Significance of Mutations Most mutations are neutral. Have little or no effect on the genes expression. Some are harmful when they produce defective proteins. Can cause human genetic disorders. Associated with different types of cancer. Helpful mutations are the key to evolution. They help an organism survive in its environment.