unit2 lesson1-dna
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UNIT 2 - DNA & DNA REPLICATION
CH 7.1 & 7.2 P. 137-148
THE UNITS OF DNA
DNA is a polymer. The monomer units of DNA are
nucleotides, and the polymer is known as a "polynucleotide."
Each nucleotide consists of a 5-carbon sugar (deoxyribose), a nitrogen containing base attached to the sugar, and a phosphate group.
NUCLEOTIDES There are four different types of
nucleotides found in DNA, differing only in the nitrogenous base. The four nucleotides are given one letter abbreviations as shorthand for the four bases.
A is for adenine
G is for guanine
C is for cytosine
T is for thymine
Purine & Pyrimidine Bases Adenine and guanine are purines. Purines are the larger of the two types
of bases found in DNA. Cytosine and thymine are pyrimidines.
DNA BACKBONE
The DNA backbone is a polymer with an alternating sugar-phosphate sequence.
The deoxyribose sugars are joined to phosphate groups in ester links, also known as "phosphodiester" bonds. – Important bonds that can’t break
DNA DOUBLE HELIX DNA is a normally double stranded
macromolecule. Two polynucleotide chains, held together by weak hydrogen bonds, form a DNA molecule.– Note H-bonds are an attraction that can
pull apart and go back together relatively easily
P. 144 FIG 7-11 Also note the two strands run in
opposite directions
FEATURES OF THE DOUBLE HELIX The two polynucleotide chains run in opposite
directions The sugar-phosphate backbones of the two
DNA strands wind around the helix axis like the railing of a spiral staircase
The bases of the individual nucleotides are on the inside of the helix, stacked on top of each other like the steps of a spiral staircase.
SEE FIG 7-10 p. 143 in your TEXT BOOK
SO WHAT IS THE POINT? DNA is the brains of every cell because
it contains all of the genes that are the codes for making proteins
PURPOSE OF DNA
DNA has two major purposes– DNA REPLICATION
http://www.youtube.com/watch?v=rpwjZX_z5rg
– PROTEIN SYSNTHESIS
DNA REPLICATION Replication = when more cells need to
be produced, COMPLETE copies of the original DNA must be made – MITOSIS - nuclear division plus cytokinesis,
to produces two identical daughter cells for growth and development of an organism
– MEIOSIS - results in the production of gametes with only 1 set of DNA
(more details later!)
PROTEIN SYNTHESIS
Protein synthesis = when proteins are needed as enzymes that control all of the reactions in a cell, PARTIAL copies of a piece of DNA called a gene must be transcribed to be then translated into an amino acid polymer = protein = enzyme
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