DNA and RNA Replication Unit 6

Something to think about.. When a species reproduces, there is genetic continuity maintained from one generation to the next. WHAT is responsible for this continuity? HOW does this continuity happen?

What is DNA? DNA = DeoxyriboNucleic Acid Genetic material present in ALL organisms Different for each individual Found in nucleus Polymer- nucleic acids Monomer = nucleotides What three ‘parts’ are nucleotides made of? a. Phosphate group b. Sugar c. nitrogen base (A,T,C,G)

Nucleotides Monomer 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 Nitrogen Bases “Pure As Gold” Purines Pyrimidines Adenine, Guanine Cytosine, Thymine A, G C, T 2 carbon rings 1 carbon ring “Pure As Gold”

Nitrogen Base Pairing Adenine ALWAYS pairs with Thymine 2 hydrogen bonds Cytosine ALWAYS pairs with Guanine 3 hydrogen bonds “AT C-G”

DNA Code The order of the 4 nitrogen bases is what causes each individual’s DNA to be unique! Pictured below are small segments of DNA from three organisms, how do they compare? Plant Mammal Bacteria

DNA Code If we looked at the total DNA of each of the below organisms, which would have DNA with the least amount of base pairs? Why? Plant Mammal Bacteria

Structure of DNA Double Helix

Double Helix Which 2 scientists are credited with the discovery of the structure of DNA? James Watson & Francis Crick (1953) Double Helix Nobel Prize for Medicine in 1962

Structure of DNA Double Stranded “Backbone” = alternating phosphates and sugars (deoxyriboses) Middle Portion = bases A-T (bonded by 2 H-bonds) C-G (bonded by 3 H-bonds) In 3D: forms twisted ladder (spiral staircase)

Double Helix

On the diagram on the right, circle 1 nucleotide

DNA Replication DNA copying Why? 4 Steps in order for genetic material to be passed on to the next generation and to preserve genetic continuity 4 Steps

DNA Replication “Unzip DNA twisted ladder” (HELICASE) Break H bonds between bases

DNA Replication Match correct nucleotides according to base pair rules (DNA POLYMERASE) There are free floating nucleotides in nucleus Remember: A-T, G-C

DNA Replication Bonding-hydrogen bonds form between bases; and phosphates bond to sugar molecules to form the ‘backbone’ of DNA Bonding continues until 2 new strands have completely formed RESULT = 2 copies of the original DNA molecule

DNA Replication Pink = parent strand Blue = daughter strands

DNA Replication DNA Replication Simulation