chapter 12.1 dna
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Chapter 12.1 DNA. DNA’s Responsibilities. Genes carry information from one generation to the next Genes determine the heritable characteristics of organisms Genes can be replicated or copied exactly. DNA’s Components. DNA is a nucleic acid It has monomers called nucleotides - PowerPoint PPT PresentationTRANSCRIPT
Chapter 12.1DNA
Genes carry information from one generation to the next
Genes determine the heritable characteristics of organisms
Genes can be replicated or copied exactly
DNA’s Responsibilities
DNA is a nucleic acid◦ It has monomers called nucleotides
Each nucleotide is composed of three basic parts: 5 carbon sugar – deoxyriboseA phosphate groupA nitrogenous base
DNA’s Components
There are four nitrogenous bases categorized into two groupsPurines: (two rings)
Adenine (A) Guanine (G)
Pyrimidines: (one ring) Cytosine (C) Thymine (T)
Nitrogenous Bases
DNA can be considered to be like a ladder
The sugar and phosphate groups make up the backbone of the molecule, or the sides of the ladder◦ They alternate along the sides
The nitrogenous bases stick out of the sides of the sugar◦ They make up the rungs of the ladder
DNA’s Structure
Erwin ChargaffRealized the number of
A’s equals the number of T’s and that the number of G’s equals the number of C’s
Base pairing ruleA = T G = C Purines Pyrimidines
Rosalind FranklinUsed x-ray
diffraction to gather information about DNA structure
◦ Revealed that DNA is in helix form (coil or twisted ladder)
Made 1st 3-D model of a DNA molecule◦ Used the work of Chargaff and Franklin to create
this model
DNA structure is called a double helix, in which two strands are wound around each otherThe two strands are connected by hydrogen bonds
Watson and Crick
DNA and ChromosomesChromosomes are
tightly wound up DNA strands
Increased organization allows for the tremendous length of DNA to fit into the nucleus of the cell
DNA is tightly wound around proteins called histones8 histones + DNA = nucleosome◦ These form chromatin
Chromatin tightly wound up makes a chromosome
http://www.youtube.com/watch?v=yqESR7E4b_8&feature=related
Chromosome Structure
Prokaryotic Chromosomes Prokaryotic chromosomes are located
floating in the cytoplasm of the cell (not in the nucleus)They are circular in shape (not “X shape” like
in eukaryotes)