1. THE GENETIC MATERIAL OF LIFE UNIT 3
DNA
THE GENETIC MATERIAL OF LIFE
UNIT 3

2. What is DNA? Stands for: DeoxyriboNucleic Acid
Molecule that stores genetic information in all organisms
DNA is stored in the nucleus of your cells

3. Fun DNA Facts!
DNA is too small to see, but under a microscope it looks like a twisted up ladder!
DNA stands for: D: Deoxyribose N: Nucleic A: Acid
Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!

4. Structure of dna

5. DNA Structure DNA is a long chain made up of units called nucleotides
Each nucleotide has three parts:
Phosphate group (one phosphorus/3 oxygens)
Deoxyribose (ring-shaped sugar)
Nitrogen-containing base
There are only four types of nucleotides—based on what type of nitrogen base they have

6. Structure of Nucleotides
Phosphate group
Nitrogen Base: Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Deoxyribose

7. The letter refers to the DNA bases as well as the nucleotide
One molecule of DNA contains BILLIONS of nucleotides, but there are only 4 types:
Adenine (A)
Guanine (G)
Thymine (T)
Cytosine (C)
The letter refers to the DNA bases as well as the nucleotide

8. Base Pairing
DNA is a double helix structure—this means that there are two strands of DNA that wind together like a twisted ladder
The strands are bonded together at the bases

9. The bases always pair up in the same way based on base pairing rules:
Adenine bonds with Thymine
Adenine
Thymine
Cytosine bonds with Guanine
Cytosine
Guanine

10. Pairing up
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4

11. THE DOUBLE HELIX
bases
sugar-phosphate
chain

12. The structure of DNA consists of two strands wrapped around each other in a double helix

13. So if one strand is… what is the other strand, based on base pairing rules?C G
- T
- A
- G
- C

14. Try it out… DNA structure worksheet!
See it DNA structure in action:
Build a virtual DNA strand:
DNA candy model!

15. DNA Replication

16. DNA Replication
Before a cell divides, it must make a copy of its DNA

17. (A mistake is called a mutation)
The steps of DNA Replication:
DNA is unwound
DNA polymerase adds nucleotides, according to base pair rules
The strand is proofread as nucleotides are added, and mistakes can be fixed if the wrong base was added
(A mistake is called a mutation)
DNA polymerase continues adding nucleotides until a STOP signal is reached

18. DNA Replication
in action

19. Try it out!
Make sure to click on DNA Replication NOT protein synthesis because we have not learned about protein synthesis yet! DNA Paperclip Replication Activity

20. Transcription

21. RNA (this molecule is used during transcription)
RNA: RiboNucleic Acid
Chain of nucleotides made of:
Sugar
Phosphate group
Nitrogen-containing base
It’s a temporary copy of DNA that is used and then destroyed

22. DNA vs. RNA DNA RNA Its sugar is deoxyribose
Both have a sugar, phosphate, & base
DNA
RNA
Its sugar is deoxyribose
Bases are: Adenine, Thymine, Guanine, Cytosine
Double strand of nucleotides
Its sugar is ribose (has one extra oxygen)
Bases are: Adenine, Uracil, Guanine, Cytosine (uracil pairs w/ adenine)
Single strand of nucleotides

23. Transcription
Copying a sequence of DNA to make a complementary strand of RNA
This is catalyzed (allowed to happen) by RNA polymerase

25. Basic steps of Transcription in Cells
DNA strands unwind
RNA polymerase copies one strand of DNA and creates a complementary strand of RNA nucleotides (known as mRNA)
Once the gene has been copied, mRNA detaches from DNA
mRNA moves out of the nucleus and into the cytoplasm

26. Step 1 Step 2 Step 3 transcription complex start site nucleotides DNA
RNA copying
RNA
Step 3

27. Types of RNA
Three types of RNA are formed during transcription, they will be used in translation:
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)

28. Watch transcription in action

29. translation

30. Translation
Process that converts (translates) mRNA into a protein —called protein synthesis
mRNA is a message that codes for a protein when it attaches to a ribosome in the cytoplasm of the cell
Each combination of 3 nucleotides (known as a codon) on the mRNA codes for an amino acid —groups of amino acids become proteins in the cell

32. Steps of Translation mRNA moves out of nucleus and into the cytoplasm
mRNA attaches to ribosome
Transfer RNA (tRNA) decodes the mRNA into amino acids, which link together into proteins
Protein (chain of amino acids) detaches from ribosome and goes off to work in the cell

33. Check it out…
Go to the following website to see translation (also called PROTEIN SYNTHESIS) in action
Make sure to click on Protein Synthesis!!

34. Genetic Code
tRNA matches each codon in mRNA to three nucleotide bases called anticodons on tRNA
This anticodon has a specific amino acid attached that will eventually form a chain of amino acids to make a protein :
There are 64 possible 3 letter combinations BUT only 20 amino acids….
SO, some Codons code for more than one amino acid

35. Codon
Anticodon

36. Different codons code for different amino acids!!!

37. Transcription vs. Translation Review
Process by which genetic information encoded in DNA is copied onto messenger RNA
Occurs in the nucleus
DNA mRNA
Translation
Process by which information encoded in mRNA is used to assemble a protein at a ribosome
Occurs on a Ribosome
mRNA protein

38. Mutations

39. Mutation A Mutation is a change in an organism’s DNA
It’s a mistake made during replication or transcription
Can be:
Harmful: diseases, disorders or deformities
Helpful: help the organism to survive
Neutral: organism is unaffected

40. Passing on Mutations
If a mutation occurs in a sperm or egg cell, the mutation IS PASSED on to offspring
If a mutation occurs in a body cell, it only affects the organism and IS NOT PASSED on to offspring

41. Causes of Mutations During DNA Replication:
Base-pairing mistakes can happen but most are fixed
Exposure to powerful Chemicals:
Cigarette smoke, smokeless tobacco, exhaust from burning petroleum fuels, pesticides, herbicides, alcohol, sawdust from CCA lumber, paints, mineral spirits & oils, asbestos, etc.
Exposure to powerful radiation:
Gamma Rays (nuclear fuel & bombs)
X rays (at hospitals & dental offices)
UV rays (from sunlight and tanning beds)

42. Sickle Cell Anemia

43. Point Mutations
An alteration in DNA sequence caused by a single nucleotide base change, insertion, or deletion

44. Types of Mutations
Insertion-- changes the number of DNA bases in a gene by
adding a piece of DNA. The protein made by the gene
may not function properly.
Deletion-- changes the number of DNA bases by removing a
piece of DNA. This could be removing a few base pairs
within a gene or an entire gene/several neighboring
genes. This may alter the function of the resulting
protein(s).
Duplication-- consists of a piece of DNA that is mistakenly
copied one or more times. This may alter the function
of the resulting protein.

45. What happens when a protein is altered due to a mutation?
To function correctly, each cell depends on thousands of proteins to do their jobs in the right places at the right times.
A mutation can cause the protein to malfunction or to be missing entirely.
An altered protein can disrupt normal development or cause a medical condition.
Examples: Breast Cancer, Down’s syndrome, Crohn’s disease, Hemophilia, Duchenne Muscular Dystrophy

46. What do you know?
Mutations concept map