1. DNA

2. James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA

3. Structure of DNA – A Double Helix
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Go to Section:

4. Section 12-2
Nucleosome
Chromosome
DNA
double
helix
Coils
Supercoils
Histones
Go to Section:

5. X-ray diffraction photograph of the DNA double helix

6. 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.
Remember that proteins are made of Amino Acids

7. DNA is an ideal genetic material because
Can store information
Replicate
Undergo changes (variation or mutations)

8. DNA and RNA are polynucleotides
Both DNA and RNA are polynucleotides.
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

9. Structure of a nucleotide
Composed of 3 parts
1. Pentose Sugar
2. Phosphate Group
3. Nitrogenous Base

10. Pentose Sugar A nucleotide is made of 3 components: A Pentose sugar
This is a 5 carbon sugar
The sugar in DNA is deoxyribose.
The sugar in RNA is ribose.

11. Structure of a nucleotide
Composed of 3 parts
1. Pentose Sugar
2. Phosphate Group
3. Nitrogenous Base

12. Structure of a nucleotide
Composed of 3 parts
1. Pentose Sugar
2. Phosphate Group
3. Nitrogenous Base

13. Nitrogenous Base A Nitogenous base In DNA the four bases are:
Thymine
Adenine
Cytosine
Guanine
In RNA the four bases are:
Uracil P
Nit Base
Sugar

14. Base pairing
The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA.

15. Complementary base pairing
Adenine Thymine
Guanine Cytosine
In RNA the following substitution
Adenine Uracil

16. The Rule: Adenine always base pairs with Thymine (or Uracil if RNA)
Cytosine always base pairs with Guanine.
This is beacuse there is exactly enough room for one purine and one pyramide base between the two polynucleotide strands of DNA.

17. Structure of DNA Molecules

21. Replication

22. DNA Replication Section 12-2 Go to Section: Original strand
DNA polymerase
New strand
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand
Go to Section:

23. Replication of DNA and Chromosomes
Speed of DNA replication: 3,000 nucleotides/min in human ,000 nucleotides/min in E.coli
Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt)

24. DNA Replication Step 1 Unwinding
1. The DNA must be unwound and bonds between the bases broken so that the two strands become separated. .
2. An enzyme helicase unzips and separates the two strands.

25. DNA Replication Step 2 Complimentary Base Pairing
1 Each strand serves as a template for the synthesis of a new strand.
2 DNA polymerase adds nucleotides to match to the nucleotide present on the template strand. A is paired with T and G with C.

26. DNA Main Ideas DNA is coded information
Contains four kinds of bases (represented by A, G, C, and T).
Is replicated by unwinding and adding complimentary bases.

27. A replicating Drosophila chromosome

29. Which type of compound is found in every DNA molecule. (1. ) starch (2
Which type of compound is found in every DNA molecule? (1.) starch (2.) nitrogenous base (3.) lipid  (4.) amino acid
2. In a DNA molecule, a base pair could normally be composed of (1.) adenine-thymine (2.) adenine-uracil (3.) thymine-guanine (4.) adenine-guanine
3. The deoxyribose part in the name deoxyribonucleic acid refers to the (1.) rungs of the sugar ladder (2.) bonds that hold the two strands together (3.) sugar component of DNA (4.) type of helical arrangement
4. A nucleotide of DNA could contain (1.) adenine, ribose, and phosphate (2.) nitrogenous base, phosphate, and glucose (3.) phosphate, deoxyribose, and thymine (4.) uracil, deoxyribose and phosphate
5. A molecular group consisting of a sugar molecule, a phosphate group, and a nitrogen base is a (1.) nucleoprotein (2.) amino acid (3.) nucleic acid (4.) nucleotide

30. 6. Which statement concerning nucleic acids is FALSE?
(1.) DNA is a single stranded molecule.  (2.) DNA forms a twisted helix.
(3.) RNA contains ribose sugar. (4.) RNA may contain uracil.
7. A nucleotide would least likely contain the element
(1.) carbon (2.) nitrogen (3.) phosphorus (4.) sulfur
8. Which nitrogenous bases is NOT found in DNA?
(1.) thymine (2.) uracil (3.) adenine  (4.) guanine (5.) cytosine
9. During the replication of the DNA molecule, bonds are broken between the     (1.) nitrogenous bases (2.) phosphate groups (3.) pentose sugars (4.) sugars and phosphates
10. After the replication of the DNA molecule is completed, each of the two daughter cells is usually composed of
(1.) fragments from both strands of the parent DNA molecule  (2.) one nucleotide strand exactly like the parent nucleotide strands
(3.) nucleotides slightly different from the parent DNA molecule
(4.) nucleotides like the parent DNA molecule except that thymine is substituted for uracil

31. 11. In nucleotides, the letters A, G, C, and T represent (1
11. In nucleotides, the letters A, G, C, and T represent  (1.) phosphate groups       (2.)  nitrogenous bases  (3.) deoxyribose sugars  (4.) ribose sugars
12. In a portion of a gene, the nitrogenous base sequence is T-C-G-A-A-T. Which       nitrogenous base sequence would normally be found bonded to this section of the gene?       (1.) A-C-G-T-A-A  (2.) A-G-C-T-T-A  (3.) A-C-G-U-U-A  (4.) U-G-C-A-A-U
13. How would the complementary strand of DNA appear if the original strand of       DNA contained the bases T-A-G-C in that order? (1.) U-A-C-G (2.) G-C-A-T       (3.) T-A-C-G (4.) A-T-C-G

32. Protein Synthesis
How do we get from To

33. Bring amino acids to ribosome
Concept Map
Section 12-3
RNA
can be
Messenger RNA
Ribosomal RNA
Transfer RNA
also called
which functions to
also called
which functions to
also called
which functions to
mRNA
Carry instructions
rRNA
Combine
with proteins
tRNA
Bring amino acids to ribosome
from to
to make up
DNA
Ribosome
Ribosomes
Go to Section:

34. Protein Synthesis Transcription
The genetic code is transcribed to form a compliment mRNA strand
Translation
The modified genetic code is transcribed into specific proteins

35. Function of DNA
DNA provides genetic code needed by cells to produce proteins.
Proteins make structures and form enzymes which control cellular functions and traits.

36. DNA vs RNA DNA Deoxyribose Thymine Double chain RNA Ribose
Uracil is substituted for Thymine A-U, C-G
Single chain

37. Types of RNA mRNA – Messenger RNA tRNA – Transfer RNA
rRNA – ribosomal RNA

38. Bring amino acids to ribosome
Concept Map
Section 12-3
RNA
can be
Messenger RNA
Ribosomal RNA
Transfer RNA
also called
which functions to
also called
which functions to
also called
which functions to
mRNA
Carry instructions
rRNA
Combine
with proteins
tRNA
Bring amino acids to ribosome
from to
to make up
DNA
Ribosome
Ribosomes
Go to Section:

39. Types of RNA
mRNA
Carries DNA message from DNA in nucleus to sites of protein synthesis in the cytoplasm on ribosomes.

40. Types of RNA 3-base code (triplet) is an “anticodon”
mRNA
Carries DNA message from DNA in nucleus to sites of protein synthesis in the cytoplasm on ribosomes.
tRNA
brings specific amino acid to a specific place on mRNA
3-base code (triplet) is an “anticodon”
Protein molecule
Attached amino acid that is carried from cytoplasm to ribosomes

41. Types of RNA
mRNA
Carries DNA message from DNA in nucleus to sites of protein synthesis in the cytoplasm on ribosomes.
tRNA
brings specific amino acid to a specific place on mRNA
rRNA
holds mRNA and tRNAs in place to form chains of peptides

42. Steps for Protein Synthesis
Transcription steps 1-3
Translation steps 4-6

43. DNA Transcription DNA must be copied to messenger RNA (mRNA)
mRNA goes from nucleus to the ribosomes in cytoplasm
mRNA complements known as codons
Only 3 nucleotide “letters” long
Remember RNA has uracil (U) instead of thymine (T)!

44. Transcription Section 12-3 RNA polymerase DNA RNA Go to Section:
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA
Go to Section:

45. Steps for Protein Synthesis
1. DNA in nucleus unzips and provides template for mRNA.

46. Transcription Step 1 making a mRNA copy of DNA
The part of the DNA molecule (the gene) that the cell wants the information from to make a protein unwinds to expose the bases.
Free mRNA nucleotides in the nucleus base pair with one strand of the unwound DNA molecule.

47. Steps for Protein Synthesis
1. DNA in nucleus unzips and provides template for mRNA.
2. Transcription: DNA is transcribed to form a compliment mRNA strand which leaves the nucleus

48. Transcription Step 2
The mRNA copy is made with the help of RNA polymerase. This enzyme joins up the mRNA nucleotides to make a mRNA strand.
This mRNA strand is a complementary copy of the DNA (gene)
The mRNA molecule leaves the nucleus via a nuclear pore into the cytoplasm

49. Steps for Protein Synthesis
1. DNA in nucleus unzips and provides template for mRNA.
Transcription: DNA is transcribed to form a compliment mRNA strand which leaves the nucleus
mRNA binds to a ribosome in the cytoplasm.

50. Animal Cell Animal Cell (attached) Ribosome Nucleolus (free) Nucleus
Centrioles
Nucleolus
Nucleus
Nuclear
envelope
Rough
endoplasmic
reticulum
Golgi apparatus
Smooth
Mitochondrian
Cell
Membrane
Ribosome
(free)
(attached)
Animal Cell

51. Transcription Reminders
The template strand is the DNA strand being copied
The mRNA strand is the same as the DNA strand except Us have replaced Ts

52. Protein Translation
Modified genetic code is “translated” into proteins
Codon code is specific, but redundant!
20 amino acids
64 triplet (codon) combinations

53. Translation Section 12-3 mRNA Go to Section: Nucleus Messenger RNA
Messenger RNA is transcribed in the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.
Methionine
Ribosome
mRNA
Start codon
Go to Section:

54. Translation (continued)
Section 12-3
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
mRNA
Translation direction
Ribosome
Go to Section:

55. Translation
Step 4. For each codon on the mRNA, a specific tRNA, with its anticodon, is brought in with an amino acid bound to it.

57. tRNA structure 3-base code (triplet) is an “anticodon”
ONLY THREE NUCLEOTIDES LONG
Protein molecule
Attached amino acid that is carried from cytoplasm to ribosomes

58. tRNA in cytoplasm has a codon attached to an amino acid

59. Translation
Step 4. For each codon on the mRNA, a specific tRNA, with its anticodon, is brought in with an amino acid bound to it.
Step 5. Translation: As the ribosome reads each codon, new tRNA molecules are brought it to form a polypeptide. (assembly line)

60. Translation mRNA to Polypeptide

61. Translation
Step 4. For each codon on the mRNA, a specific tRNA, with its anticodon, is brought in with an amino acid bound to it.
Step 5. Translation: As the ribosome reads each codon, new tRNA molecules are brought it to form a polypeptide.
Step 6. The chain becomes a polypeptide chain, which can fold in specific ways to become proteins. Proteins become structures and enzymes, which control cellular functions and traits.

63.  The Genetic Code
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