1. Chapter 12

2. DNA structure and replication RNA
Transcription
Translation
Protein synthesis
Amino acids

3. Discovery of the Genetic Material
After the rediscovery of Mendel’s work, scientist began to look for the molecule involved in inheritance.
For many years, scientists struggled to determine if DNA or protein was the source of genetic information.
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4. Discovery of the Genetic Material
Miescher
1860’s
“nuclein”
Griffith
First major experiment searching for the genetic material
Involved transformation between two forms of S. pneumoni
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5. Chromosome Structure
To fit into a cell, DNA coils around a group of beadlike proteins
Group together into chromatin fibers
Supercoil to form a chromosome.
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DNA: The Genetic Material

7. Chromosome Structure Eukaryotes DNA in individual chromosomes Nucleus
Prokaryotes
DNA in Cytoplasm
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DNA: The Genetic Material

8. DNA Structure
James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA.
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9. DNA Structure Double helix
X-ray diffraction techniques indicated that DNA was a double helix, or a twisted ladder shape.
Formed by two strands of nucleotides twisted around each other.
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10. The structure of DNA and RNA
Genetic material of living organisms is either DNA or RNA.
DNA – Deoxyribonucleic acid
RNA – Ribonucleic acid
Genes are lengths of DNA that code for particular proteins.

11. DNA and RNA are Polynucleotides
Both DNA and RNA are polynucleotides.
Poly = many
They are made up of smaller molecules called nucleotides.
DNA is made of two polynucleotide strands:
RNA is made of a single polynucleotide strand:
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide
Nucleotide

12. DNA Structure Nucleotides
Nucleotides are the subunits of nucleic acids, and consist of
5-carbon sugar
Phosphate group
Nitrogenous base

13. DNA Structure Pentose Sugar 5 carbon sugar DNA – deoxyribose
RNA - ribose

14. DNA Structure Phosphate Group
Link the sugar of one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide.

15. AS Biology. Gnetic control of protein structure and function
DNA Structure
A Nitrogenous base:
In DNA the four bases are:
Thymine
Adenine
Cytosine
Guanine
In RNA the four bases are:
Uracil
AS Biology. Gnetic control of protein structure and function

16. Four DNA bases Four kinds of nitrogenous bases: Purine bases
Pyrimidine bases

17. DNA: Complimentary base pairing
Adenine pairs with Thymine
A = T
Bond Type =
double
Cytosine pairs with Guanine
C = G
Triple

18. DNA Structure DNA often is compared to a twisted ladder.
Rails of the ladder are represented by the alternating deoxyribose and phosphate.
The pairs of bases (cytosine-guanine or thymine- adenine) form the steps.

19. DNA STRUCTURE VIDEO YUMMY GUMMY DNA

20. DNA Replication (in nucleus)
Matching bases allows DNA to be easily copied

21. Making new DNA Replication Copying DNA
DNA starts as a double-stranded molecule
matching bases (A:T, C:G)
then it unzips…

22. DNA Replication
Strands “unzip” at the weak bonds between bases

23. DNA Replication Enzyme DNA polymerase adds new bases
DNA bases in nucleus
Enzyme
DNA polymerase
adds new bases
DNA
polymerase

24. Copying DNA Build daughter DNA strand
use original parent strand as “template”
add new matching bases
synthesis enzyme = DNA polymerase
DNA
Polymerase

25. New copies of DNA Get 2 exact copies of DNA to split between new cells
polymerase
DNA
polymerase

26. Copied & Paired Up Chromosomes
centromere

27. Comparing DNA Replication
Eukaryotes and Prokaryotes
Eukaryotic DNA unwinds in multiple areas as DNA is replicated.
In prokaryotes, the circular DNA strand is opened at one origin of replication.
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28. Replication of DNA and Chromosomes
Speed of DNA replication: ,000 nucleotides/min in human ,000 nucleotides/min in E.coli
Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt)
AS Biology. Gnetic control of protein structure and function

29. 3

30. Base your answer to the following question on the diagram below which represents a portion of a double-stranded DNA molecule and on your knowledge of biology.
The base sequence of strand II is most likely:
C-A-C-T-G-G G-T-G-U-C-C
G-G-T-C-A-C G-T-G-A-C-C 4

31. Practice
On your paper, complete the missing DNA strand by adding the complementary bases.
A T C G T T G C C A T C
T A G C A A C G G T A G

32. DNA, RNA & Protein
Chapter 12: Section 3

33. Central Dogma
Investigate how DNA served as a genetic code for the synthesis of proteins.
Geneticists accept that the basic mechanism for reading and expressing genes is from DNA to RNA to protein.
This is referred to as the central dogma of biology:
DNA codes for RNA, which guides the synthesis of proteins.
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35. RNA differs from DNA DNA has a sugar deoxyribose
1. RNA has a sugar ribose
DNA has a sugar deoxyribose
2. RNA contains uracil (U)
DNA has thymine (T)
3. RNA molecule is single-stranded
DNA is double-stranded

36. Three Types of RNA Central Dogma
Messenger RNA (mRNA): long strands of RNA that are formed complementary to one strand of DNA; direct synthesis of a specific protein
Ribosomal RNA (rRNA): associates with proteins to form ribosomes in the cytoplasm
Transfer RNA (tRNA): smaller segments of RNA that transport amino acids to the ribosome
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37. Central Dogma Transcription
First step synthesis of mRNA from DNA in a process called transcription.
RNA polymerase moves along the DNA strand in a 3’ to 5’ direction, synthesizing mRNA.
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39. Practice
Make the complementary RNA strand for the single strand of DNA below:
A A T C A T C A C G T T
U U A G U A G U G C A A
T A C C C G A G G T A G C C G C G T A T T
A U G G G C U C C A U C G G C G C A U A A

40. Reading the genetic code
The genetic code is responsible for building all the proteins in the body using 20 different amino acids.
How many 3 letter words can you make from the letters A,T,G and C?
Answer: 64

41. The three-base code in DNA or mRNA is called a codon.
The Code
Scientists hypothesized that the instructions from protein synthesis were encoded in DNA.
Experiments during the 1960s demonstrated that the DNA code was a three-base code.
The three-base code in DNA or mRNA is called a codon.
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DNA, RNA, and Protein

42. Codons
A three letter “word” that specifies an amino acid.

43. A. Messenger RNA (mRNA) A U G C aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1
methionine
glycine
serine
isoleucine
alanine
stop
codon
protein
Primary structure of a protein
aa1
aa2
aa3
aa4
aa5
aa6
peptide bonds

44. The Code
Translation
After synthesis, mRNA moves from the nucleus into the cytoplasm, where it connects to a ribosome.
The mRNA code is read and translated into a protein through a process called translation.
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DNA, RNA, and Protein

45. tRNA molecules act as the interpreters of the mRNA codon sequence.
The Code
Translation
tRNA molecules act as the interpreters of the mRNA codon sequence.
The tRNA is activated by an enzyme that attaches a specific amino acid to the end.
The middle of the folded tRNA contains an anticodon, a complementary sequence to the mRNA codon.
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DNA, RNA, and Protein

46. The role of the ribosome
The Code
The role of the ribosome
Ribosomes provide a site for protein synthesis.
When mRNA leaves the nucleus, the two ribosomal subunits come together to hold the mRNA in place for translation.
The ribosome structure has grooves that hold the mRNA and serve as tRNA sites for amino acid attachment.
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47. From DNA to Protein

48. found inside the nucleus
DIFFERENCES
DNA
RNA
Deoxyribonucleic acid
Double strand
G, C, A, T
deoxyribose sugar
Inheritance of traits & enzyme production
NUCLEIC ACIDS
C, G, A
found inside the nucleus
Ribonucleic acid
Single strand
G, C, A, U
ribose sugar
protein synthesis
SIMILARITIES

49. If the cell is a school… The Nucleus is the school office
The Nucleolus is the principal’s office
The DNA is the principal
Ribosomes are the cafeteria ladies
mRNA is the from the principal to the cafeteria lady

50. Review/Explain: Types of Nucleic Acids
What are the two types of nucleic acids?
Ribonucleic Acid (RNA)
Single Stranded
Deoxyribonucleic Acid (DNA)
Double Helix
(Twisted Ladder)

51. DNA Deoxyribose Sugar Base Pairs A-T G-C Phosphate Most Importantly---
Contains the Code for ALL the Proteins in the Body

52. RNA Ribonucleic Acid Sugar + Phosphate backbone Differs from DNA
Single Stranded
Ribose Sugar
Base Pairs A-U, G-C
RNA assists DNA in manufacturing needed proteins

53. Questions Name one difference between DNA and RNA.
DNA – Double Helix, RNA – Single Stranded
DNA --- A-T, RNA ---A-U
DNA ---Deoxyribose Sugar, RNA--- Ribose
What is a similarity of DNA and RNA?
G binds with C in both DNA and RNA
Both have sugar and phosphate backbone

54. Gel Electrophoresis use to separate DNA fragments determine
relationships
used in forensics

55. Study the diagram on the left side of this slide.
Which of the following
DNA samples of
individuals are most
closely related?
EXPLAIN.
DNA sample 1 & 7

56. Crime Scene #1

57. Crime Scene #2

58. Crime Scene #3

59. Paternity

60. Paternity #1
Dad 2

61. Paternity #2

62. WHO ARE THE PARENTS?

63. WHO ARE THE PARENTS? Child 1 Child 2 Child 3 Child 4
Mom and Dad Mom Neither