Nucleotides

             I. nucleotides: sub units „³ DNA
             B. 5-carbon sugar molecule (deoxyribose)
             Chargaff „³ base pairing rule: 1 = 3 and 2 = 4
             II. Maurice Wilkins and Rosalind Frankilin „³ X-ray diffraction photos of DNA molecule
             - DNA molecules: tightly coiled helix and composed of two or three chains of nucleotides
             III. Chargaff builds a model of the double helix: ¡§a spiral staircase¡ of 2 strands of nucleotides twisting around a central axis.
             A. alternating sugar and phosphate units
             B. purine and pyrimidines paired up
             - A can only form hydrogen bonds with T
             - C can only for ¡§ ¡§ with G.
             „³ 2 strands that are complementary to each other
             A. Replication: process of synthesizing a new strand of DNA.
             B. Helices: open up the double helix by breaking the hydrogen bonds that link the complementary bases.
             C. Two strands separated: additional enzymes and proteins attach to the individual strands and hold them apart „³ twisting prevented
             D. Replication fork : where double helix separates
             1. DNA polymerases: enzymes that move along each strand „³ adding nucleotides to the exposed bases.
             „³ one old and one new DNA strand
             - genes hold info specifying how to build particular proteins
             - affects the phenotype of an individual because of the activity of the protein that it specifies
             - DNA encoded info that specifies particular proteins; each gene is made of a specific sequence of nucleotides
             A. interruped by necleotides that have no coding info.
             1. Introns:: noncoding sequences/ intervening
             2. Exons :nucleotide segments that code for amino acids
             -stitched together once all introns are removed
             II. Multigene families: clusters of almost identical sequences; cells exist in mult
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Nucleotides. (1969, December 31). In MegaEssays.com. Retrieved 07:46, March 28, 2024, from https://www.megaessays.com/viewpaper/48543.html