1. Question: Why don’t we all look alike?
DNA – The Code for Life
Question: Why don’t we all look alike?

2. All Living Things… Have cells.
All cells contain the genetic instructions that make an organism unique.  Adapted to environment, appearance, preferences, behaviors, survival instincts, etc.

3. DNA
We get our genetic codes/instructions from DNA that is located inside every cell.

4. Jurassic Park DNA Scene
(Youtube.com)

5. Deoxyribonucleic acid
DNA
DNA stands for –
Deoxyribonucleic acid
Functions of DNA:
1. Carries the codes to make proteins.
Carries the genetic material that is passed on from the parents to the offspring.

6. Discovery of DNA
Invented X-ray diffraction photography. Photo used to determine the shape of DNA is spiral.
Rosalind Franklin -

7. Won the Nobel Peace Prize in Chemistry in 1961.
DISCOVERY OF DNA
James Watson and Francis Crick used the information from Franklin and other scientists to build a 3-D model of DNA.
Won the Nobel Peace Prize in Chemistry in 1961.

8. Structure of DNA Shape of DNA - Like a twisted rope ladder.
This shape is called Double Helix.
A single spiral would be called Helix.

9. STRUCTURE OF DNA Side Pieces (The Rope Part)
Are alternating units of a (1) five-carbon sugar and a (2) phosphate group. These go down both sides of the molecule
phosphate
Sugar (called deoxyribose)

10. STRUCTURE OF DNA Nitrogen Bases (Steps of the ladder) - Adenine – A
Thymine – T
Cytosine – C
Guanine - G
The bases are connected to the sugar only !!!!!

11. Adenine always goes with Thymine
STRUCTURE OF DNA
The nitrogen bases fit together in this way:
Adenine always goes with Thymine
Cytosine always goes with Guanine
The bases are held together by a weak hydrogen bond. Two (2) bonds between A and T, three (3) bonds between C and G.

13. Purines and Pyrimidines
Purines: A & G
Pyrimidines: T & C
Both basically serve the same
purpose but structure
is different. Structure allows
these to be used in different
ways in cells
Purines- 2 carbon-nitrogen
rings, 4 nitrogen
atoms
Pyrimidines-1 carbon-nitrogen
ring, 2 nitrogen atoms

14. STRUCTURE OF DNA
These three parts form the basic unit of DNA called the NUCLEOTIDE. (subunits of DNA)
phosphate
Nitrogen base
Can be A, T, C or G
Sugar
(deoxyribose)

15. Adenine always goes with Thymine
STRUCTURE OF DNA
The nitrogen bases fit together in this way:
Adenine always goes with Thymine
Cytosine always goes with Guanine
The bases are held together by a weak hydrogen bond. Two (2) bonds between A and T, three (3) bonds between C and G.

16. phosphate
adenine
sugar
thymine
cytocine
guanine

17. STRUCTURE OF DNA
One complete turn of the double helix is 10 base pairs or 10 steps on the ladder

18. DNA Nucleotide Drawing

19. Where is DNA located?
DNA molecules are coiled up inside of EVERY SINGLE CELL!
The structures that DNA is coiled into are called CHROMOSOMES.  This is how the DNA molecules actually fit inside of tiny cells.

20. Chromosomes Definition: The structure that DNA is organized in.
They come in pairs, half from each parent.

21. NUMBERS OF CHROMOSOMES VS COMPLEXITY
The number of chromosomes in the cells of eukaryotes differs from one kind of organism to another and has NOTHING to do with the complexity of the organism.
FOR EXAMPLE:
Goldfish - 98
Wheat - 42
Human - 46
Potato - 48
Fruit fly - 8
A fern called Ophioglossum reticulatum has 1,260 chromosomes per cell, more than any other known organism.

22. The 23rd pair is different. These are the sex chromosomes.
CHROMOSOME ARRANGEMENT
All regular body cells have all the same parts in multi-cellular organisms and the same # of chromosomes.
There are 46 chromosomes in human body cells.
Chromosomes always come in pairs.
In humans there are 46 chromosomes for a total of 23 pairs.
22 of the pairs are similar.
The 23rd pair is different.
These are the sex chromosomes.
Male xy
Female xx

23. CHROMOSOME ARRANGEMENT
HUMAN BODY CELLS HAVE 46 CHROMOSOMES OR 23 PAIRS.
Bone cell
Nerve cell
BULLFROG BODY CELLS HAVE 26 CHROMOSOMES OR 13 PAIR.
FRUIT FLY BODY CELLS HAVE 8 CHROMOSOMES OR 4 PAIR.

24. Gene: segment of DNA on your chromosomes that determines your traits.

26. Traits
Characteristics about an organism that are determined by the information carried on genes (segments of DNA).

27. Siblings???
If you have a sibling, and you both get the DNA from your (same) mom & dad, why don’t you look exactly alike?????

28. Siblings
Since sex cells only get half the number of chromosomes, each sex cell does not get the same exact half.
During sex cell formation, chromosomes randomly reconnect to form a new gene variety.
(We will talk about this more in reproduction… next unit…)

30. How does DNA copy itself?
Purpose: DNA copies itself to ensure that each new cell that is produced gets the correct number of chromosomes and receives an EXACT copy of the DNA molecule.
This is called DNA REPLICATION.
The DNA molecule serves as its own pattern or template so as an exact copy can be made.

31. Replication #1
Replication #2

32. STEPS OF DNA REPLICATION
1. DNA untwists and unzips down the hydrogen bonds. This is why the bonds had to be WEAK.
2. New nucleotides fill in the naked ends produced by the unzipping process.
3. Nucleotides continue to fill in until the entire strand is complete.
4. This results in 2 new identical DNA molecules.

33. What happens when there is a problem during replication?
A permanent change in the sequence of DNA is known as a mutation
(a small change that occurs during replication but is caught/corrected is known as a point mutation)

34. DNA REPLICATION What if there is a mistake?
There is always a chance that the wrong nucleotide bonds to another. HOWEVER, DNA has a special enzyme that is responsible for “reading” the bases and recognizing and replacing damaged or wrong nucleotides. This PROOFREADING allows for only one (1) error in ONE BILLION nucleotides.

35. Possible causes of mutations
Error during replication
Error during fertilization (reproduction)
Outside factors such as X-rays and chemical have ben known to change or breakdown chromosomes

36. Common mutations (in humans)
Pimples/acne, high fertility (twins), heart disease, diabetes, stroke, high blood pressure, color blindness, heterochromia (two different colors in one eye OR two different colored eyes), red hair, down syndrome, blue eyes, freckles

37. Different types of mutations

38. Different types of mutations: Substitution/Inversion
Switches a section of base pairs
Switching an A or a G

39. Different types of mutations: Insertion and Deletion
Insertion= extra base pairs are inserted into a new plane
Deletion= a section of DNA is lost or deleted

40. Different types of mutations: Duplication
A piece of DNA is abnormally copied one or more times

41. Different types of mutations: Translocation
Altered chromosome arrangement

42. We have been told that DNA is the blueprint for life, BUT what does that mean?
DNA holds the instructions that tell a cell how to construct amino acid chains.
SO WHAT?
That is important because amino acid chains build proteins.
Proteins build cells
AND