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ALL organisms Genetic material present in ALL organisms nucleus Usually found within the nucleus Different Different for each individual within a species DeoxyriboNucleic Acid DNA = DeoxyriboNucleic Acid NUCLEOTIDE Polymer made of repeating NUCLEOTIDE monomers
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DNA
Structure Replication
Something to think about… When a species reproduces, there is
genetic continuity that is maintained from one generation to the next. WHAT is responsible for this continuity? HOW does this continuity happen?
What is DNA? Genetic material present in ALL
organisms Usually found within the nucleus Different for each individual within a
species DNA = DeoxyriboNucleic Acid Polymer made of repeating
NUCLEOTIDE monomers
What is a NUCLEOTIDE? A molecule made of the following 3 parts:
1. a 5-Carbon sugar group (deoxyribose) 2. a phosphate group 3. a nitrogen base – 4 different possibilities!
(5 Carbon sugar)
4 Different Nitrogen Bases Adenine (A) Guanine (G)
Purines (2 carbon rings) Cytosine (C) Thymine (T)
Pyrimidines (1 carbon ring)
It is the arrangement of these 4 different nucleotides that allows DNA to be so unique!
4 Different Nucleotides Adenine ALWAYS
pairs with Thymine (double bond)
Cytosine ALWAYS pairs with Guanine
(triple bond)
To Help you Remember: AT C-G
The Double Helix 2 Scientists credited
with discovering the structure of DNA in 1953: James Watson &
Francis Crick (Watson & Crick)
Watson & Crick Model of structure = DOUBLE HELIX
They received the Nobel Prize (Medicine) in 1962
The Double Helix The key to Watson and
Crick’s discovery was an X-ray diffraction image (known as Photo 51) of DNA recorded by Rosalind Franklin Both the image and Franklin’s
interpretation of the image were shown to Watson without her permission
Watson, Crick, and Wilkins (the man who gave Watson the image) received the Nobel Prize▪ Franklin had died 4 years earlier
The Double Helix Characteristics:
1. DOUBLE stranded molecule
2. phosphate & sugar portion of nucleotides form the “backbone” of each strand
3. Nitrogen base of one strand forms a HYDROGEN BOND with the nitrogen base of a second strand
4. In 3-Dimensional space, it forms a “twisted ladder” (spiral staircase)
The Double Helix
DNA Replication
DNA must be able to make a copy of itself in order for genetic material to be passed on to the next generation and to preserve genetic continuity.
DNA Replication
This replication process occurs in 4 basic steps.
DNA Replication
Step 1 – HELICASE (an enzyme) cause the hydrogen bonds between the nitrogen bases to break (“Unzips the ladder”)
Step 2 – DNA POLYMERASE (another enzyme!) is responsible for reading the DNA template and matching up the complimentary nucleotide from the free floating nucleotides present in the nucleus
DNA Replication Step 3 – Base pairs form hydrogen
bonds and the phosphate group of one nucleotide bonds with the sugar of another to form the “backbone”
Step 4 – Bonding continues along the strands until 2 new strands are formed
RESULT = 2 new EXACT copies of the original DNA molecule!
DNA Replication
Pink = parent strand
Blue = daughter strands
DNA Replication
DNA Replication Simulation
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