1. Molecular Genetics
Glencoe Chapter 12

2. DNA: The Genetic Material
Griffith-first major experiment that led to the discovery of DNA as genetic material
Worked with two strains of bacteria and found that one could be transformed into another

3. DNA: The Genetic Material
Avery-identified transformation molecule as DNA
Hershey and Chase-definite evidence that DNA is the transforming factor
Used radioactive labeling to trace DNA and protein

4. DNA: The Genetic Material
X-ray diffraction- aims X-ray at DNA molecule
Indicated double helix structure
Twisted ladder shape
Rosalind Franklin

5. DNA: The Genetic Material
Watson and Crick
Used Franklin’s photo
Measured width of helix and spacing of bases to build a model of double helix

6. DNA: The genetic material
DNA structure
Nucleotides: subunits of nucleic acids that consist of a five carbon sugar, a phosphate group, and a nitrogenous base
DNA: adenine (A), guanine (G), Cytosine (C), Thymine (T)
RNA: adenine (A), guanine (G), Cytosine (C), Uracil (U)

7. DNA: The Genetic Material
Chargaff’s rule
A=T, G=C

8. DNA: The Genetic Material
Sugar phosphate backbone
Antiparallel strands-one strand runs 5’3’ and other runs 3’5’

9. DNA: The Genetic Material

10. DNA: The Genetic Material
Chromosome Structure
51 million-245 million base pairs
DNA coils around histones to form a nucleosome
Phosphate groups in DNA create negative charge
Histones are positively charged
Nucleosomes group in chromatin fibers then coil

11. Replication of DNA

12. Replication of DNA Helicase-unwinds DNA
RNA primase-adds short segment of RNA called primer
DNA polymerase-adds nucleotides to the 3’ end

13. Replication of DNA Leading strand-built continuously
Lagging strand-built discontinuously in segments called Okazaki fragments

14. Replication of DNA
Joining
Ligase

15. Replication of DNA

16. DNA, RNA and Protein Central Dogma DNARNAprotein DNA Transcription
Figure 10.6A
DNA
Transcription
RNA
Protein
Translation
Central Dogma
DNARNAprotein

17. DNA, RNA and Protein RNA Single stranded Contains sugar ribose
Base uracil replaces thymine

18. DNA, RNA and Protein
RNA

19. DNA, RNA and Protein
Transcription-DNA code is transferred to mRNA in the nucleus
DNA is unzipped and RNA polymerase binds and adds nucleotides to 3’ end

20. DNA, RNA and Protein Transcription Initiation Elongation Termination
RNA polymerase
DNA of gene
Promoter
DNA
Terminator
Area shown
In Figure 10.9A
Growing
RNA
Completed RNA
polymerase
Figure 10.9B
Transcription
Initiation
Elongation
Termination
1 Initiation
2 Elongation
3 Termination

21. DNA, RNA and Protein RNA processing
Exon Intron Exon Intron Exon
DNA
Cap
Transcription
Addition of cap and tail
RNA
transcript
with cap
and tail
Introns removed
Tail
Exons spliced together
mRNA
Coding sequence
Nucleus
Cytoplasm
RNA processing
Introns-segments not in the final mRNA
Exons-sequences that remain in final mRNA
5’ cap and poly-A tail

22. DNA, RNA and Protein Genetic code
Codon- 3-base code for amino acids in mRNA

23. DNA, RNA and Protein tRNA Attached to amino acids
Has anticodon complementary to codons on mRNA

24. DNA, RNA and Protein
Ribosome
2 subunits
EPA sites

25. DNA, RNA and Protein Translation
mRNA leaves nucleus and associates with ribosomal subunits
tRNAs add their amino acids to polypeptide chain as mRNA moves through the ribosome one codon at a time
Stops when stop codon is reached

26. DNA, RNA and Protein

27. Gene Regulation and Mutation
Prokaryote Gene Regulation
Gene regulation-ability for an organism to control which genes are transcribed
Operon- section of DNA that contains gene for proteins needed for a specific metabolic pathway
Operator-acts as on/off switch for transcription
Promoter-where RNA polymerase first binds
regulatory gene
genes coding for proteins

28. Gene Regulation and Mutation
trp operon
Cluster of genes coding for production of tryptophan
Repressible operon- transcription is normally turned off
When tryptophan is present, no need to produce more

29. Gene Regulation and Mutation
Tryptophan binds to repressor protein which binds to the mRNA, blocking RNA polymerase from binding
With low levels of tryptophan, repressor will not bind to mRNA and genes will be transcribed.

30. Gene Regulation and Mutation
lac operon
When lactose is present, makes enzymes to use lactose as energy source
Inducible operon
Repressor protein inactive when bound to lactose

31. Gene Regulation and Mutation
Eukaryotic gene regulation
Transcription factors-proteins that ensure that a gene is used at the right time and that proteins are made in the right amounts
One set guide and stabilize RNA polymerase
Another set help control rate of transcription
Activators and repressors
Complex structure and coiling inhibits transcription

32. Gene Regulation and Mutation
Hox genes-responsible for general body pattern
Genes that control differentiation,

33. Gene Regulation and Mutation
Mutation-permanent change made to a cell’s DNA
Point mutation-change in one base pair
Substitution
Missense-changes one amino acid
Silent-does not change the amino acid
Nonsense-changes to a stop codon
Insertion-gain of nucleotides
Deletion-loss of nucleotides
Frame shift-caused by deletion or insertion, changes reading frame

35. Gene Regulation and Mutations
Causes of mutations
DNA polymerase adding wrong nucleotides
Has proofreading system, very uncommon
Mutagens-substances (chemicals, radiation) that cause mutations by changing chemical structure of bases