1. Chromosomes/DNA

2. Chromatin
When the cell is not dividing (resting) the chromosomes are all intertwined and are called chromatin.

3. Chromosomes
When the cell starts to divide the Chromosome looks like the above picture before it makes a copy of itself.

4. 46 Chromosomes before they make a copy of themselves
46 Chromosomes before they make a copy of themselves. Note how they occur in Pairs.

5. Genes are arranged along the DNA of the chromosome
Chromosome Structure
Chromosomes are made up of
60% protein
40% DNA
Genes are arranged along the DNA of the chromosome

6. Chromosomes which have made a copy of themselves
Protein balls called histones
DNA

7. Non Coding DNA Large sections of the chromosome do not contain genes
This DNA is called Non Coding DNA
It’s function is not yet clear

8. Chromosome structure

9. Chromosomes Thread like structures Contains DNA Contains Protein
Contains Genetic Information
Found in the nucleus of all cells
46 chromosomes in a human cell
Occur in pairs

10. Genes
Remember a Gene is a section of DNA that controls the production of a protein.
3% of DNA are genes, the rest is non coding

11. Structure of DNA-Ordinary
Two stranded joined together by bases
Bases-Adenine(A), Thymine (T), Guanine (G) and Cytosine (C)
Adenine pairs with Thymine
Guanine pairs with Cytosine
It forms a twisted ladder shape

12. Structure of DNA- Higher
Each strand consists of a phosphate (PO4), a sugar (deoxyribose-5 carbon sugar) and a nitrogen base (A, T, G or C)
Phosphate, deoxyribose and base=Nucleotide
A and G are Purines
T and C are Pyrimdines
Bases are bonded by weak hydrogen bonds
2 bonds between A and T
3 bonds between G and C

13. A Nucleotide Base Sugar P O OH HO NH2 N - OH O CH2 H OH Phosphate 2’3’ 4’ 5’ 1’ OH

15. Purine Bases Adenine and Guanine Double ringed molecular structures O
Known as Purine Bases
NH2 O N NH
Guanine N
Adenine
NH2

16. Pyramidine Bases Thymine and Cytosine single ringed structures NH2
Known as Pyramidine bases
CH3 N O NH
Thymine
(DNA) N O
NH2
Cytosine

17. Base Pairing Guanine And CytosineH O N
Guanine - N O H
Cytosine + + - - +
Three Hydrogen Bonds

18. Base Pairing Adenine And Thymine- +
Adenine
CH3 N O H + -
Thymine
Two Hydrogen Bonds

19. Double Helix Rosalind Franklin discovered the shape of DNA
The outside strand are made from the Phosphate and deoxyribose sugar and the steps are the base pairs
These are then twisted to form a spiral structure

22. Replication Step 1 = DNA uncoils
Step 2 = Enzyme breaks weak hydrogen bonds
Step 3 = Spare bases enter nucleus & attach to exposed complementary bases. Each side of DNA acts as a template for new DNA
Each strand is half new DNA half old DNA
Both DNA strands are identical
Step 4 = DNA recoils

23. Step 1

24. Step 2

25. Step 3

26. Step 4

27. Why is replication important
DNA is able to produce exact copies of itself. This means that the same DNA is passed on to each new generation of cells

28. RNA
Ribonucleic Acid Operates with DNA to make proteins Has Uracil instead of Thymine

29. Differences between DNA and RNA
Double strand
Sugar is deoxyribose
Has Thymine
Much longer
Self replicating
Only in the nucleus
RNA
Single strand
Sugar is ribose
Has Uracil
Short molecule
Not self replicating
Found in nucleus and cytoplasm

30. Similarities between DNA and RNA
Both are nucleic acids
Both contain
adenine, guanine and cytosine nucleotides
Operate together to produce specific proteins

31. PROTEIN SYNTHESIS
Higher Level

32. The Genetic Code
A gene is a sequence of many bases required for the production of a particular protein.
Proteins (1000s) made from amino acids joined together in a specific sequence
20 different amino acids which can be joined in 1000s of different combinations each producing a new protein
DNA codes for the sequence of these amino acids
Each amino acid comes from 3 consecutive bases = triplet or codon

34. Base
A, T, C, G
Letter
A, B, R, T
Triplet
ATA
Word
BART
Gene
ATA GTC CAT GTC ATC…
Paragraph
Bart had a cat that sat …
Genome
Book

35. Gene Expression Remember………
This is the precise way in which the genetic information in a gene is decoded in the cell and used to make a protein.

36. For Protein Synthesis You need: A supply of amino acids – cytoplasm
Instructions as how to join the amino acids
together – genetic code
An assembly line – ribosomes
A messenger to carry information from DNA to ribosomes

37. Protein Synthesis - Steps
3 stages:
1. Initiation
2. Trancription
3. Translation
Remember: DNA  RNA  Protein

38. Remember RNA Ribose: smaller sugar than deoxyribose of DNA Phosphate
4 Nitrogenous Bases A,G,U,C
RNA is single stranded and thus smaller & able to leave the nucleus of the cell

39. DNA  RNA  Protein Eukaryotic Cell Transcription Translation DNA mRNA
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
mRNA
Ribosome
Protein
Eukaryotic Cell

40. Prokaryotic Cell – No nucleus
DNA  RNA  Protein
Transcription
Translation
DNA
mRNA
Ribosome
Protein
Prokaryotic Cell – No nucleus

41. Learning Check What is RNA composed of?
How does RNA (ribonucleic acid) differ from DNA (deoxyribonucleic acid)?
What are the three stages in Protein synthesis?

42. 1. Initiation
Enzymes in nucleus start to unwind the DNA at the site of the gene.

43. 2. Transcription Eukaryotic Cell DNA mRNA Ribosome Protein Nuclear
membrane
Transcription
Translation
DNA
mRNA
Ribosome
Protein
Eukaryotic Cell

44. 2. Transcription
The transfer of information in the nucleus from a DNA molecule to an RNA molecule.
Only 1 DNA strand serves as the template
Starts at promoter DNA (AUG)
Ends at terminator DNA (stop)
When complete, mRNA molecule is released into the cytoplasm

45. Video Clip available in extra material folder

46. 2. Transcription
Takes places in the nucleus of the cell The process by which the information from DNA is transferred to RNA.
The exposed DNA bases are matched up with RNA bases in the nucleus to form mRNA.

47. 2. Transcription
DNA
mRNA
RNA Polymerase
Enzyme

48. It was made in the nucleus by transcription from a DNA molecule.
This is a molecule of messenger RNA.
It was made in the nucleus by transcription from a DNA molecule.
codon
A U G G G C U U A A A G C A G U G C A C G U U
mRNA molecule

49. A. Messenger RNA (mRNA)
Carries the information for a specific protein.
Made up of 500 to 1000 nucleotides long.
Made up of codons (sequence of three bases)
Each codon is specific for one amino acid.

50. A. Messenger RNA (mRNA) Primary structure of a protein A U G C aa1 aa2
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

51. 3. Translation Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell

52. Video Clip available in extra material folder

53. 3. Translation Synthesis of proteins in the cytoplasm
Involves the following:
1. mRNA (codons)
2. tRNA (anticodons)
3. rRNA
4. ribosomes
5. amino acids

54. B. Transfer RNA (tRNA) Made up of 75 to 80 nucleotides long.
Picks up the appropriate amino acid floating in the cytoplasm
Transports amino acids to the mRNA.
Has anticodons that are complementary to mRNA codons.
Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds.

55. C. Ribosomal RNA (rRNA)
Made up of rRNA is 100 to 3000 nucleotides long.
Important structural component of a ribosome.
Associates with proteins to form ribosomes.

56. Ribosomes Large and small subunits.
Composed of rRNA (40%) and proteins (60%).
Both units come together and help bind the mRNA and tRNA.

57. Ribosomes
Large
subunit
mRNA A U G C
Small subunit

58. 3. Translation Three parts: 1. initiation: start codon (AUG)
2. elongation:
3. termination: stop codon (UAG)

59. Translation
In the cytoplasm, translation occurs. The mRNA binds to a ribosome.
The strand of mRNA is pulled through the ribosome three bases at a time, in triplets.
Each of these triplets on the mRNA strand is called a codon.

60. tRNA
Transfer RNA (tRNA), reads the strand of mRNA and translates it into a strand of amino acids.
A molecule of tRNA has at one end a set of three bases that will complement the mRNA strand; this is called the anticodon.

61. tRNA
If the 3 base anticodon of the tRNA complements the 3 base codon of the mRNA, they briefly combine.
The amino acid is left behind when the tRNA leaves.
As each codon is read, the next tRNA brings in a new amino acid and the polypeptide (protein) chain grows.
This requires enzymes and ATP.

62. It was made in the nucleus by transcription from a DNA molecule.
This is a molecule of messenger RNA.
It was made in the nucleus by transcription from a DNA molecule.
codon
A U G G G C U U A A A G C A G U G C A C G U U
mRNA molecule

63. A ribosome attaches to the mRNA molecule.
A U G G G C U U A A A G C A G U G C A C G U U

64. Amino acid
U A C
tRNA molecule
A transfer RNA molecule arrives.
It brings an amino acid to the first three bases (codon) on the mRNA.
anticodon
The three unpaired bases (anticodon) on the tRNA link up with the codon.
A U G G G C U U A A A G C A G U G C A C G U U

65. U A C
C C G
Another tRNA molecule comes into place, bringing a second amino acid.
Its anticodon links up with the second codon on the mRNA.
A U G G G C U U A A A G C A G U G C A C G U U

66. C C G
A A U
Another tRNA molecule brings the next amino acid into place.
A U G G G C U U A A A G C A G U G C A C G U U

67. C C G
C C G
A peptide bond joins the second and third amino acids to form a polypeptide chain.
A U G G G C U U A A A G C A G U G C A C G U U

68. A C G
G U C
The process continues.
The polypeptide chain gets longer.
This continues until a termination (stop) codon is reached.
The polypeptide is then complete.
A U G G G C U U A A A G C A G U G C A C G U U

70. End Product
The end products of protein synthesis is a primary structure of a protein.
A sequence of amino acid bonded together by peptide bonds.
aa1
aa2
aa3
aa4
aa5
aa200
aa199

71. Functional Protein
The protein now has to undergo folding and the addition of bonds
Folding allows the Protein to reach its 3D (Tertiary Shape) which influences its Function.

72. Types of RNA Three types of RNA: A. messenger RNA (mRNA)
B. transfer RNA (tRNA)
C. ribosome RNA (rRNA)
Remember: all produced in the nucleus!

73. Learning Check
The anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid.
What would be the DNA base code for this amino acid?

74. Answer:
tRNA - UAC (anticodon)
mRNA - AUG (codon)
DNA - TAC

75. What have you learned? Can you ………………
 Outline the steps in protein synthesis
Understand that a strand of DNA is copied by transcription
Understand the role of mRNA
Know the function of a ribosome in protein synthesis
Understand the process of translation that leads to the formation of a new protein
Know that the shape of a protein determines its function

76. End