CH. 8

1. CH. 8 IDENTIFYING DNA AS THE GENETIC MATERIAL

2. 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.

3. 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?

4. Ch. 8.1 – Identifying DNA as the Genetic Material • Griffith finds a “transforming principle.” - NOTES

5. 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.

6. Ch. 8.1 – Identifying DNA as the Genetic Material • Avery Identifies DNA as the transforming principle - NOTES

7. 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? • 1st 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.

8. Ch. 8.1 – Identifying DNA as the Genetic Material • Hershey & Chase confirm that DNA is the genetic material – NOTES

9. 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.

10. Review • 1. What did Hersey & Chase know about bacteriophages that led them to use these viruses in their DNA experiments?

11. ANSWER: • That bacteriophages are made up of a protein coat surrounding DNA.

12. 8.2 – Structure of DNA • DNA is composed of 4 types of nucleotides (monomer): • Nucleotide composed of: • Phosphate group • 5 carbon sugar • Nitrogen base

13. 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

14. 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.

15. ANSWER TO QUESTIONS • 1. THE 4 NITROGEN BASES. • 2. THE NITROGEN BASES, BECAUSE THE REMAINING PARTS OF THE NUCLEOTIDE ARE IDENTICAL.

16. Watson & Crick Developed an accurate model of DNA - NOTES

17. 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.

18. 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.

19. 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

20. 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.

21. 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.

22. DNA Replication

23. 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

24. 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.

25. 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

26. 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)

27. 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.

28. 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. 8.11 visualizes transcription

29. 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.

30. 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

31. 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.

32. GENETIC CODE

33. Genetic Code

34. 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 CCC A A U G A • A) methionine(start), proline, glutamine, stop

35. 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

36. 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. 8.16 Translation • Read pg. 247

37. 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

38. TRANSLATION

39. 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

40. 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:

41. 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.

42. 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

43. 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 • http://staff.tuhsd.k12.az.us/gfoster/standard/bmut.htm

44. 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