Dna and Nucleotide Chains Essay

Dna and Nucleotide Chains Essay Dna and Nucleotide Chains Essay Chapter 10 Objective Questions 1. Describe the structure and function of DNA. DNA structure is a nucleic acid, meaning it is made up of a chain of nucleotides. Nucleotides are made up of phosphate, deoxyribose sugar, and a nitrogen base. The shape of a DNA is a twisted double helix, with two strands. DNA has 2 nucleotide chains which are like the ladder which are held by covalent bonds which are strong. The sides of the ladder are the alternating phosphate and deoxyribose. DNA is antiparallel so sides run in opposite directions. The rungs of the ladder are the bases. The bases hold the nucleotide chains together by hydrogen bonds from complimentary pairing. The A and T pairing have 2 hydrogen bonds and the C and G pairing have 3 hydrogen bonds. A and G are purines which have two rings which C and T are pyrimidine which have one ring. The function of DNA is to store and transmit genetic information, to control the production of proteins, to make parts of a cell and to reproduce cells. 2. Explain the process of mitosis. Mitosis occurs in 4 phases. The first phase is prophase. In prophase, the condensing chromosomes are visible under a microscope. The nuclear membrane breaks down and stores in the vesicles. Spindle fibers form microtubules in the cytoplasm. The spindle fibers attach to centromere and centriole. Polar spindles extend centriole to centriole. The centrioles move to opposite poles. The second phase is metaphase. Metaphase is when the replicated chromosomes line up in the middle or the equator. The third stage is anaphase. In anaphase the enzyme breaks down the centromere. Then the chromatids separate. The spindle fibers pull the chromatid to the polar region. This makes sure that every cell gets every chromosome. The last phase of mitosis is telophase. The nuclear membrane is reforming in telophase. Also the spindle fibers are disappearing. The chromosomes are uncoiling as well. The cleavage furrow shows the division point of the cell. Then during cytokinesis the cell divides into two. P lant cells have to form a cell plate which is cell wall material carried