Presentation on theme: "CH. 8 IDENTIFYING DNA AS THE GENETIC MATERIAL. CH. 5 & 6 REVIEW ANSWER THE FOLLOWING QUESTIONS: 1. What macromolecule group does DNA & RNA belong in?"— Presentation transcript:
CH. 8 IDENTIFYING DNA AS THE GENETIC MATERIAL
CH. 5 & 6 REVIEW ANSWER THE FOLLOWING QUESTIONS: 1. What macromolecule group does DNA & RNA belong in? 2. What monomer do we use to assemble the macromolecule group from question #1.
CH. 5 & 6 REVIEW ANSWER THE FOLLOWING QUESTIONS: 3. What is a nucleotide? 4. What would a nucleotide for DNA contain? 5. What would a nucleotide for RNA contain?
Ch. 8.1 – Identifying DNA as the Genetic Material Griffith finds a “transforming principle.” - NOTES
Ch. 8.1 – Identifying DNA as the Genetic Material Griffith finds a “transforming principle.”- QUESTION & ANSWER: 1. What was “transformed” in Griffith’s experiment? That the R bacteria in the presence of the dead S bacteria became pathogenic. 2. Explain how the results support the experimenters conclusion. The mice dying when they shouldn’t have means that the S bacteria must have contained some information that was able to change the harmless bacteria t deadly bacteria.
Ch. 8.1 – Identifying DNA as the Genetic Material Avery Identifies DNA as the transforming principle - NOTES
Ch. 8.1 – Identifying DNA as the Genetic Material Avery Identifies DNA as the transforming principle – QUESTION & ANSWERS: 1. How did Avery and his group identify the transforming principle? 1 st identifying the 2 components: proteins & DNA Used enzymes to break down the protein & the R-bacteria were still transformed to S bacteria killing the mice. Only when an enzyme to break down DNA did the transformation failed to occur. 2. Explain how the results support their conclusions for the transforming principle. By using the enzyme to break down DNA and not having the transformation occur.
Ch. 8.1 – Identifying DNA as the Genetic Material Hershey & Chase confirm that DNA is the genetic material – NOTES
Ch. 8.1 – Identifying DNA as the Genetic Material Hershey & Chase confirm that DNA is the genetic material – QUESTIONS & ANSWERS: 1. Summarize how Hershey & Chase confirmed that DNA is the genetic material. A: They labeled the protein of bacteriophages with radioactive sulfur and their DNA with radioactive phosphorus. The bacteriophages were allowed to infect bacteria. 2. Summarize why the bacteriophage was an excellent choice for research to determine whether genes are made of DNA or proteins? A: A bacteriophage consists of little more than a protein coat surrounding DNA. The protein coat is left behind when the viral DNA enters a bacterium. 3. Explain how the results support their conclusions. A: That the phage’s DNA had entered the bacteria, but the protein had not, convincing scientists that the genetic material is DNA & not protein.
Review 1. What did Hersey & Chase know about bacteriophages that led them to use these viruses in their DNA experiments?
ANSWER: That bacteriophages are made up of a protein coat surrounding DNA.
8.2 – Structure of DNA DNA is composed of 4 types of nucleotides (monomer): Nucleotide composed of: Phosphate group 5 carbon sugar Nitrogen base
DNA is composed of 4 types of nucleotides con’t. Nucleotide in DNA is composed of: Phosphate group Deoxyribose sugar Nitrogen base Cytosine = C Thymine = T Adenine = A Guanine = G Nucleotide in RNA is composed of: Phosphate group Ribose sugar Nitrogen base Cytosine = C Uracel = U (replaces thymine) Adenine = A Guanine = G Letter abbreviations refer both to the base & to the nucleotides that contain that base
DNA is composed of 4 types of nucleotides con’t. CHARGAFF’S RULE: A = T G = C QUESTION: What is the only difference among the 4 DNA nucleotides? Which part of a DNA molecule carries the genetic instructions that are unique for each individual; the sugar-phosphate backbone or the nitrogen-containing bases? Explain.
ANSWER TO QUESTIONS 1. THE 4 NITROGEN BASES. 2. THE NITROGEN BASES, BECAUSE THE REMAINING PARTS OF THE NUCLEOTIDE ARE IDENTICAL.
Watson & Crick Developed an accurate model of DNA - NOTES
Watson & Crick Developed an accurate model of DNA – QUESTION & ANSWER: What bases are considered pyrimidines & purines? Pyrimidines = T & C Purines = A & G How did the Watson & Crick Model explain Chargaff’s rules? The pyrimidine – thymine a single ringed base pairs with a purine – adenine a double ringed base so that the double helix will be able to maintain the correct shape.
Nucleotides always pair in the same way. DNA nucleotides of a single strand are joined together by covalent bonds connecting the sugar of one nucleotide to the phosphate of the next nucleotide. Alternating sugars & phosphates form the sides of a double helix sort of like a twisted ladder. DNA double helix is held together by hydrogen bonds between the bases in the middle.
Nucleotides always pair in the same way – QUESTIONS & ANSWERS: What sequence of bases would pair with the following sequence: T T A C G C G A C A A T G C G C T G
8.3 – DNA Replication Replication copies the genetic information Watson & Crick’s experiments showed that one strand of DNA is used as a template to build the other strand Guarantees that each strand of DNA is identical.
Proteins carry out the process of replication How : DNA is unzipped at numerous places (H bonds broken) Free floating nucleotides pair with the exposed bases (template strands) DNA polymerase bonds the nucleotides together to form the new strands that are complementary to the template strand (original strand). Creates 2 identical molecules of DNA. Each DNA molecule has an original & a new strand. Why DNA replication is called semiconservative replication.
Replication is fast & accurate Replication is fast because the DNA strand is opened at hundreds of different points & allowing nucleotides to be added at many spots at the same time. Proofreading is carried out at the same time that nucleotides are added. DNA polymerase can detect errors & make corrections. Pg. 238, fig. 8.9 shows this process
8.4 TRANSCRIPTION RNA carries DNA’s instructions Central Dogma Information flows from DNA to RNA to proteins Transcription converts a DNA message into an intermediate molecule, called RNA. Translation interprets an RNA message into a string of amino acids, called a polypeptide. Either a single polypeptide or many polypeptides working together make up a protein.
RNA carries DNA’S instructions con’t. Prokaryotic cells: Replication, transcription, and translation all occur in the cytoplasm at approximately the same time. Eukaryotic cells: Replication, transcription, and translation occur in different locations. Replication & transcription – nucleus Translation – occurs in the cytoplasm
RNA carries DNA’s instructions con’t. RNA acts as an intermediate link between DNA in the nucleus & protein synthesis in the cytoplasm. Gets used then destroyed. RNA is single stranded, contains ribose sugar & has uracil instead of thymine A (DNA) = U (RNA) T (DNA) = A (RNA) G (DNA) = C (RNA) C (DNA) = G (RNA)
Transcription makes 3 types of RNA Transcription is the process of copying a sequence of DNA to produce a complementary strand of RNA. Part of the chromosome, called a gene, is transferred into an RNA message. Transcription is catalyzed by RNA polymerase.
Transcription produces 3 major types of RNA molecules mRNA (messenger RNA) – an intermediate message that is translated to form a protein rRNA (ribosomal RNA) – forms part of ribosomes, a cell’s protein factories tRNA (transfer RNA) – brings amino acids from the cytoplasm to a ribosome to help make the growing protein. Pg. 241, Fig visualizes transcription
Transcription vs. replication Similarities Happen in nucleus of eukaryotic cells Need enzymes to begin the process Unwind the DNA double helix Complementary base pairing to the DNA strand Regulated by the cell Differences Replication makes sure each new cell will have one complete set of genetic instructions & occurs only once during each round of the cell cycle. Transcription could make hundreds or thousands of copies of certain proteins or the rRNA or tRNA molecules needed to make proteins based on the demands of the cell, using a single stranded complementary mRNA strand.
8.5 TRANSLATION Amino acids are coded by mRNA base sequences Translation is the process that converts, or translates, an mRNA message into a polypeptide. Could be 1 or more polypeptides to make up a protein Language of nucleic acids: DNA – uses 4 nucleotides = A, G, C, & T RNA – uses r nucleotides = A, G, C, & U Language of proteins uses 20 amino acids
Triplet Code Genetic code uses codons, which is read in groups of 3 nucleotide bases Codon is a 3 nucleotide sequence that codes for a particular amino acid, referred to as the reading frame. First 2 nucleotides are usually the most important in coding for an amino acid Start codon – signals the start of translation and the amino acid is methionine 3 stop codons – signal the end of the amino acid chain. If reading frame is changed, changes protein or even can prevent a protein from being made. Almost all organisms, including viruses, follows the genetic code. This allows scientists to insert a gene from 1 organism into another organism to make a functional protein.
DETERMINE WHAT AMINO ACID SEQUENCES ARE CREATED FROM THE FOLLOWING STRINGS OF NUCLEOTIDES 1) A U G A C C A A C A G C A) methionine(start), threonine, asparagine, serine 2) A U G C C C C A A U G A A) methionine(start), proline, glutamine, stop
Amino acids are linked to become a protein Review: mRNA is a short lived molecule that carries instructions from DNA in the nucleus to the cytoplasm mRNA message is read in groups of 3 nucleotides called codons How it translates the codon into an amino acid requires the use of rRNA & tRNA molecules
Amino acids are linked to become a protein Ribosomes are made of a combination of rRNA & proteins & they catalyze the reaction that forms the bonds between amino acids. Ribosomes have a large & small subunit that fit together & pull the mRNA strand through. Small unit holds the mRNA strand & the large subunit holds onto the growing protein tRNA carries amino acids from the cytoplasm to the ribosome Has an L shape to the tRNA molecule, one end of the L is attached to the specific amino acid & the other end of the L, is called the anticodon, which recognizes a specific codon. Anticodon is a set of 3 nucleotides that is complementary to an mRNA codon. PG. 246, Fig Translation Read pg. 247
8.6 – GENE EXPRESSION & REGULATION mRNA processing Important part of gene regulation in eukaryotic cells is RNA processing. mRNA that is produced by transcription needs to be edited Exons are nucleotide segments that code for parts of the protein. Introns are nucleotide segments that are located between the exons Introns are removed from mRNA before it leaves the nucleus. Exons are joined back together
8.7 MUTATIONS Some mutations affect a single gene & others affect the entire chromosome Mutation is a change in an organism’s DNA Types of gene mutations: Point mutation – a mutation in which one nucleotide is substituted for another. DNA polymerase could find & correct mistake, if not may permanently change an organism’s DNA Frameshift mutation – involves the insertion or deletion of a nucleotide in the DNA sequence Affects the polypeptide more than a point mutation (substitution) Causes the reading frame from point of insertion or deletion to change the remaining amino acids
MUTATIONS ORIGINAL NUCLEOTIDE SEQUENCE: A U G C C G U U A A C G C G A U C C G G READS: MUTATED NUCLEOTIDE SEQUENCE: A U G C A C G U U A A C G C G A U C C G G READS:
Types of chromosomal mutations: Gene duplication: During crossing over chromosomes do not align & the chromosomal segments are different sizes. The chromosome receiving the larger segment would have part of the chromosome that is duplicated. Gene deletion: During crossing over chromosomes do not align & the chromosomal segments are different sizes. The chromosome receiving the smaller segment would have part of the chromosome that is deleted. Translocation: A piece of one chromosome moves to a non- homologous chromosome.
Mutations may or may not affect phenotype. Phenotype – Collection of all of an organism’s physical characteristics. Ex: black hair, blue eyes, attached ear lobes. Chromosomal mutations Usually have big affect on organisms Ex: may break a gene causing it not to function Ex: may create a new hybrid gene with a new function Ex: may cause a gene to be more or less active Gene mutations – could have a bad affect, no affect, or create a beneficial mutation Could change the active site for an enzyme & now it cannot accept the substrate Could affect how protein folds & possibly destroying the protein’s function Could create a premature stop, making protein nonfunctional
Impact on offspring Mutations can happen in body cells & in germ cells. Body cell mutations only affect that individual Germ cell mutations may be passed to offspring Can be source of genetic variations, which is the basis of natural selection. Will affect the phenotype of offspring Could be harmful & the offspring do not develop properly or could die before reproducing Could be mutations not well suited to environment & the alleles will be removed from the population Could be a mutation that is well suited to environment & the alleles will be increased in the population
Mutations can be caused by several factors Mutagens – agents in the environment that can change DNA. Speed up the rate of replication errors Break DNA strands Cause cancer Types of mutagens: UV light Industrial chemicals