Nucleotides essays

Nucleotides essays 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 ...