1. Unit 4 Genetics
Ch. 12 DNA & RNA

2. Griffith & Transformation
Griffith injected mice with 4 different samples of bacteria
When injected separately, neither heat-killed (disease-causing bacteria), nor live, (harmless bacteria) killed the mice

3. Griffith & Transformation
The 2 types injected together, however, caused fatal pneumonia
From this experiment, biologists concluded (inferred) that genetic info. could be transferred from 1 bacterium to another

4. Griffith’s Experiment

5. Griffith & Transformation
Transformation - when 1 strain of bacteria is changed by a gene or genes from another strain of bacteria

6. Avery & DNA
Avery & other scientists performed experiments to determine if transformation required just 1 particular molecule (of a gene)
Discovered that the nucleic acid, DNA, stores & transmits genetic info. from 1 generation of an organism to the next

7. The Hershey-Chase Experiment
Studied viruses, nonliving particles smaller than a cell, that can infect living organisms
Bacteriophage - virus that infects bacteria

8. The Hershey-Chase Experiment
They performed experiments with a bacteriophage to determine its genetic material
They concluded that the genetic material of the bacteriophage was DNA & not protein

9. The Hershey-Chase Experiment

10. The Components & Structure of DNA
Genes were known to do 3 specific things:
Carry info. from 1 generation to the next
Put that info. to work by determining heritable characteristics of organisms
Be easily copied, since all of a cell’s genetic info. is replicated every time a cell divides

11. The Components & Structure of DNA
DNA is a long molecule made up of units called nucleotides
Nucleotides - made up of 3 parts:
A sugar
A phosphate group
A nitrogenous base

12. The Components & Structure of DNA
Watson & Crick developed the model of DNA, a double helix, where 2 strands were wound around each other

13. The Components & Structure of DNA
The 2 strands of DNA are held together by hydrogen bonds
Those bonds only link adenine (A) & thymine (T), & guanine (G) & cytosine (C)
Base-pairing rule - A - T, G - C

14. Structure of DNA

15. DNA & Chromosomes
Most prokaryotes have a single circular DNA molecule in their cytoplasm

16. DNA & Chromosomes
Eukaryotic DNA is located in the nucleus, in the form of a # of chromosomes
The chromosome # varies from 1 species to another

17. DNA & Chromosomes
Eukaryotic chromosomes have both DNA & protein, packed tightly together to form chromatin
Chromatin - DNA that is tightly coiled around proteins (histones)

18. DNA & Chromosomes
From largest to smallest, genetic information is arranged the following way:
Chromosomes
Genes (found on chromosomes)
DNA (makes up genes)

19. DNA Replication
Each strand of DNA could be used to make the other strand, they compliment each other
Replication - when a cell’s DNA is copied

20. DNA Replication
During DNA replication, the DNA molecule separates into 2 strands, then produces 2 new complimentary strands following base pairing rules
Each strand of the double helix serves as a template, or model, for the new strand

21. DNA Replication
DNA polymerase - enzyme that joins individual nucleotides to produce a DNA molecule
It also proofreads each new DNA strand, to help prevent errors in copying the DNA

22. DNA Replication

23. RNA & Protein Synthesis
Genes - coded DNA instruc. that control the production of proteins within the cell
The 1st step in decoding the genetic messages is to copy part of the nucleotide sequence from DNA into RNA

24. The Structure of RNA There are 3 main differences between RNA & DNA:
The sugar is a ribose, instead of deoxyribose
RNA is single-stranded
RNA contains the nitrogenous base uracil (U) instead of thymine (T)

25. Types of RNA There are 3 main types of RNA: Messenger RNA
Ribosomal RNA
Transfer RNA

26. Types of RNA
Messenger RNA - (mRNA) - RNA molecules that carry copies of instructions for assembling amino acids into proteins
They serve as “messengers” from DNA to the rest of the cell

27. Types of RNA
Ribosomal RNA - (rRNA) - form of RNA that combines with proteins to make a ribosome

28. Types of RNA
Transfer RNA - (tRNA) - RNA molecule that transfers each amino acid to the ribosome as it is specified by coded messages in mRNA

29. Types of RNA
Transcription - process of producing RNA molecules by copying part of the nucleotide sequence of DNA into a complimentary sequence of RNA
RNA polymerase - enzyme that works similarly to DNA polymerase

30. Types of RNA
During transcription, RNA polymerase binds to DNA & separates the DNA strands
RNA polymerase then uses 1 strand of DNA as a template to assemble nucleotides into a strand of RNA

31. Transcription

32. The Genetic Code
Proteins are made by joining amino acids into long chains - polypeptides
Each polypeptide has a combination of any 20 different amino acids

33. The Genetic Code
Codon - 3 consecutive nucleotides that specify a single amino acid to be added to the polypeptide

34. The Genetic Code For ex.: UCGCACGGU Read 3 at a time:
Which represents amino acids:
Serine-Histidine-Glycine

35. The Genetic Code

36. Translation
Translation - (protein synthesis) -decoding an mRNA message into a polypeptide chain (protein)
It takes place on ribosomes
Before translation occurs, mRNA is transcribed (re-written) from DNA in the nucleus & released in the cytoplasm

37. Translation
Translation then begins when an mRNA molecule in the cytoplasm attaches to a ribosome
As each codon of mRNA moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA

38. Translation
Each tRNA molecule has an anticodon - 3 nitrogenous bases that are complimentary to 1 mRNA codon
The ribosome attaches 1 amino acid to another, forming the polypeptide chain, until it reaches the “stop” codon

39. Translation
After the amino acid is attached, the tRNA molecule that brought it into the ribosome, is released back into the cytoplasm
The result is a protein

40. Translation

41. Translation

42. Summary: Role of RNA & DNA
Start with a single strand of DNA
That DNA is transcribed into RNA
The RNA is separated into codons
The codons code for amino acids, which form a polypeptide chain

44. Genes & Proteins
Many proteins are enzymes that catalyze & regulate chemical reactions
Genes for proteins can regulate the rate & pattern of growth throughout an organism
Proteins are microscopic tools that are designed to build or operate a living cell

45. Mutations
Mutations - a mistake in the DNA base sequence, may occur during copying the DNA
Changes in the genetic material

46. Kinds of Mutations Gene mutations are changes in a single gene
Chromosomal mutations are changes in the whole chromosome

47. Gene Mutations
Point mutations - change in 1 or a few nucleotides, they occur at a single point in the DNA sequence
Frameshift mutations - adding or deleting a nucleotide, shifts the “reading frame” of the genetic message

48. Chromosomal Mutations
There are 4 types of chromosomal mutations: deletions, duplications, inversions, & translocations
Deletions involve the loss of all or part of a chromosome
Duplications produce extra copies of parts of a chromosome

49. Chromosomal Mutations
Inversions reverse the direction of parts of chromosomes
Translocations occur when part of one chromosome breaks off & attaches to another

50. Significance of Mutations
Mutations cause changes in protein structure or gene activity
They are the cause of many genetic disorders
Some are associated with many types of cancer

51. Eukaryotic Gene Regulation
Genes that code for liver enzymes are not expressed in nerve cells
Cell specialization requires genetic specialization, but all cells in a multicellular organism carry the complete genetic code in their nucleus