1. Chapter 11 DNA and Protein Synthesis
Mrs. Svencer

2. 11.1 Genes are made of DNA Frederick and Griffith
Transformation –bacteria with mice
Strain A – pneumonia, fatal
Strain B – harmless
Heated strain A – harmless
Mix heated strain A and strain B - death
Harmless bacteria - “transformed”
Descendents were too - trait was passed on
Heritable change

3.                                                                                                                                                                            
Figure 11-1 Griffith showed that although a deadly strain of bacteria could be made harmless by heating it, some factor in that strain is still able to change other harmless bacteria into deadly ones. He called this the "transforming factor."

4. Oswald Avery – focused on protein and DNA
Heat strain A + strain B + protein-destroying enzymes
Offspring still transformed
Protein not accountable for transformation
Heat strain A + strain B + DNA-destroying enzymes
Colonies did not transform
Therefore, DNA = genetic material

5. Hershey and Chase – used viruses
Virus = nucleic acid in a protein coat
Bacteriophage = virus that infects bacteria
Batch 1
Labeled protein coats with radioactive sulfur
Radioactivity detected outside of the cells
Batch 2
Labeled DNA with radioactive phosphorus
Radioactivity inside cells
Therefore, phage’s DNA entered bacteria
Therefore, DNA is the hereditary material

6.                                                                                                                                                                            
Figure 11-4 Hershey and Chase offered further evidence that DNA, not proteins, is the genetic material. Only the DNA of the old generation of viruses is incorporated into the new generation.

7. 11.2 Nucleic Acids store information
DNA (deoxyribonucleic acid)
Stores genetic information
Built from nucleotides – 3 parts
1. Sugar – ring shape, “deoxyribose”
2. Phosphate group
3. Nitrogenous base – single or double ring of C and N atoms

8.                                                                  
Figure 11-5 A nucleotide has three components: a sugar, a phosphate group, and a nitrogenous base.

9. 4 bases in DNA Pyrimidines: single rings Purines: double rings
Thymine (T)
Cytosine (C)
Purines: double rings
Adenine (A)
Guanine (G)

10.                                                                                                                                   
Figure 11-6 DNA contains four different nitrogenous bases. Thymine and cytosine have single-ring structures. Adenine and guanine have double-ring

11. DNA Strands
Covalent bonds connect sugar to phosphate between nucleotides
Sugar-phosphate “backbone”
Nucleotides arrange in different
1. Numbers
2. Sequences
(combinations are unlimited)

12. Rosalind Franklin and Maurice Wilkins
X-ray crystallography
DNA = helix shape
Watson and Crick
Made model of double helix using Franklin’s pictures
Twisted ladder

13. Complementary Base Pairs
Purine + Pyrimidine
A-T (2 hydrogen bonds)
G-C (3 hydrogen bonds)

14. 11.3 DNA Replication – mechanism of inheritance (DNA – copying)
Template Mechanism
2 strands of double helix separate at origins of replication
Copying goes outward from origin in both directions, making a “bubble”
Each strand is a “template” for a new, complementary strand
Bases line up according to base-pairing rules

15.                                                                                                   
Figure 11-9 During DNA replication, the two strands of the original parent DNA molecule, shown in blue, each serve as a template for making a new strand, shown in yellow. Replication results in two daughter DNA molecules, each consisting of one original strand and one new strand.

16.                                                                                                           
Figure DNA replication begins at origins of replication and proceeds in both directions, producing "bubbles." Eventually, all the bubbles merge, resulting in two separate daughter DNA molecules.

17. New strands = daughter strands Fast and accurate
DNA polymerase (enzyme) links nucleotides together using covalent bonds
DNA opens further as nucleotides added
Eukaryotic DNA – many origins - speedy
New strands = daughter strands
Fast and accurate
1 error / billion nucleotides

18. Review: DNA Replication occurs before a cell divides during the S phase of interphase of the cell cycle

19. 11.4 Genes Provide Information for Making Proteins
Beadle and Tatum – orange bread mold
Mutant strains unable to grow on nutrient medium
Lacked single enzyme needed to produce a needed molecule
Each mutant defective in a single gene
“one gene-one enzyme” hypothesis – one gene produces one specific enzyme
NOW, “one gene – one polypeptide”

20. RNA is needed to make a protein
Nucleic Acid
RNA – ribonucleic acid
DNA – deoxyribonucleic acid
Sugar
Ribose
Deoxyribose
Nitrogenous bases
AUCG
ATCG
Shape
Single helix
Double helix

21. Gene to Protein 1. Transcription - DNA to RNA
Transcribed message (RNA) leaves nucleus to cytoplasm
2. Translation – RNA to amino acid
Codon = on RNA - 3 bases that code for amino acid

22. Table of Codons RNA Figure 11-13
61/64 code for amino acids – some amino acids coded for by more than 1 codon
Ex: UUU UUC – both code for phenylalanine
3/64 – stop codons – end of each gene sequence

23.                                                                                                           
Figure Each codon stands for a particular amino acid. (The table uses abbreviations for the amino acids, such as Ser for serine.) The codon AUG not only stands for methionine (Met), but also functions as a signal to "start" translating an RNA transcript. There are also three "stop" codons that do not code for amino acids, but signal the end of each genetic message.

24. 11.5 Two steps from Gene to Protein
Transcription: DNA to RNA
Messenger RNA (mRNA) transcribed from DNA template – only 1 strand of DNA
RNA nucleotides pair to complementary bases – AUCG
RNA polymerase - RNA nucleotides together
RNA splicing – introns are removed and exons are joined together
Therefore, mRNA has a continuous coding sequence
mRNA leaves nucleus

25.                                                                                                                                       
Figure Information flows from gene to polypeptide. First, a sequence of nucleotides in DNA (a gene) is transcribed into RNA in the cell's nucleus. Then the RNA travels to the cytoplasm where it is translated into the specific amino acid sequence of a polypeptide.

26.                                                                                                   
Figure In eukaryotes, the RNA transcript is edited before it leaves the nucleus. Introns are removed and the exons are spliced together before the "final draft" transcript moves into the cytoplasm where it gets translated.

27. Intron = noncoding region of mRNA
Exon = coding region of mRNA that is “expressed” or translated

28. Translation: RNA to protein
1. Start codon: AUG –translation begins
2. Amino acids added one-by-one to a chain of amino acids
A. tRNA (transfer RNA) translates codons of mRNA to amino acids
1. tRNA molecule binds to appropriate amino acid

29. 2. tRNA recognizes, using base-pairing rules, codons in mRNA by its own complementary anticodon
Anticodon = 3 bases at one end of tRNA
3. Other end of tRNA = where amino acid attaches
4. An enzyme links tRNA to its amino acid, using ATP

30.                                                                  
   
Figure During translation, tRNAs transport and match amino acids to their appropriate codons on the mRNA transcript. One end of the tRNA attaches to an amino acid. At the other end, a triplet of bases called the anticodon matches to the complementary mRNA codon.

31. C. ribosome connects new amino acid to the growing polypeptide chain
B. occurs at ribosome
2 subunits – made of protein and rRNA (ribosomal RNA)
Small subunit – binding site for mRNA
Large subunit – 2 binding sites for tRNA
1. “P” site (polypeptide) – holds tRNA carrying the growing polypeptide chain
2. “A” site (amino acid) – holds tRNA carrying next amino acid to be added to the chain
2 subunits hold mRNA and tRNA close together
C. ribosome connects new amino acid to the growing polypeptide chain

32.                                                                          
Figure Ribosomes bring mRNA and tRNAs together during translation. Each ribosome has an attachment site for an mRNA transcript, and two sites for tRNAs.

33. 4. Completed polypeptide set free from tRNA by hydrolysis
3. Reaches stop codon
UAA, UAG, UGA
No amino acid at “A” site
Translation stops
4. Completed polypeptide set free from tRNA by hydrolysis

34. 11.6 Mutations Mutation – any change in the nucleotide sequence of DNA
Can be
Large regions of chromosomes
Single nucleotide pairs

35. Base substitutions Replacement of 1 base or nucleotide with another
Sometimes no effect – “silent mutation”
Sometimes large effect
Why?
Several amino acids have more than 1 codon

36. More disastrous mutations
Insertion
Putting in an additional nucleotide
Deletion
Taking away 1 nucleotide
Both insertion and deletion alter the triplet groupings
Now they code for new amino acids

37. Cause of mutations Error during DNA replication
Error during crossing over in meiosis
Mutagens – physical / chemical agents that cause mutations
Ex: high-energy radiation, x-rays, UV light
Usually harmful, sometimes helpful
Ex: dark color in female tiger swallowtails

38. Mutations may be passed to offspring, if they occur in gametes
Ultimate source of genetic diversity