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Everything you wanted to know about DNA but were afraid to ask.
DNA
• A molecule that is present in all living cells and contains the information that determines the traits that a living thing inherits and needs to survive.
DNA
• Gives you your characterisitcs• Traits like eye color, height, & hair
texture.
+DNA’s Two jobs
Instruction manual that builds and maintains cells
Able to copy itself each time a cell divides
DNADOUBLE HELIX-Twisted ladder or spiral staircase
Sides of ladder are made of molecules of sugar called deoxyribose alternating with molecules of phosphate
The rungs of the ladder are made of nitrogen bases:
Adenine A
Thymine T
Guanine G
Cytosine C
A little History
Rosalind Franklin• She made the first image of an actual DNA
molecule using x-ray diffraction• Through this breakthrough we learned that
DNA has a spiral shape
Watson & Crick
• 1953’s they built the first model of DNA
• Won the Nobel Prize
Erwin Chargaff• 1950’s Chargaff found equal amounts
between certain base pairs• Adenine=Thymine• Cytosine=Guanine • Called Chargaff’s Rules
+Making copies of DNA
This occurs in interphase
Adenine always
pairs w/ Thymine
A~~~~~~~~ T
Cytosine always
pairs w/ Guanine
C~~~~~~~~G
+How copies are made
1. DNA unwinds and separates (like a zipper)
2. Bases on the open strand are used as a pattern for the new strand
3. Nitrogen bases that are floating in the nucleus pair up with the bases on each half of the unzipped DNA
4. Half of DNA is old & half is new
+ How DNA works
About 2 meters of DNA in every cell of your body
It is wound, coiled and bundled to fit inside every cell
Order of the bases on one side is a CODE that carries information
Gene- is a piece of that code that gives the cell information on the trait it controls
+Reading the Code
ATTGGCCTTGATCCCCCATAGCGATGTGTACACTC
The code is read like a book from one end to another
They are split up by 3’s
AGC is a code for a protein called “serine”
+When things go wrong!
+ Mutations: the causes
DNA damage from environmental agents such as ultraviolet light (sunshine), nuclear radiation or certain chemicals
Mistakes that occur when a cell copies its DNA in preparation for cell division.
Changes in the number, type, or order of bases on DNA
Types of MutationsDeletion- When a base is left out
Insertion- When a base is added
Substitution - Occurs when the wrong base is used
+What can happen?
Improved trait
No change
Harmful trait such as sickle cell disease
Clones
• A new organism with an exact copy of DNA from another organism
• This is CopyCat: the first cat cloneResearchers in Texas have cloned a domestic cat, producing a two-month-old kitten called CopyCat.