DNA Structure and Replication

Nucleic Acids store and transmit hereditary, or genetic, information. store and transmit hereditary, or genetic, information. are polymers assembled from individual monomers known as nucleotides. are polymers assembled from individual monomers known as nucleotides.

Nucleotides Nucleotides consist of three parts (subunits): Nucleotides consist of three parts (subunits): 5-carbon sugar 5-carbon sugar phosphate group (–PO 4 ) phosphate group (–PO 4 ) nitrogenous base. nitrogenous base.

DNA Structure DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds DNA is found in the nucleus! DNA is found in the nucleus!

Base Pairing Hydrogen bonds Hydrogen bonds are responsible for holding the two strands of nucleic acids together.

Base Pairing These bonds form only between certain base pairs—adenine with thymine, and guanine with cytosine. This fit between A–T and G–C nucleotides is known as base pairing. See Video.Video

Nucleotides are made up of: a.) Nucleic acids b.) Nitrogenous base, 5-carbon sugar, and phosphate group c.) Nitrogenous base, guanine, and phosphate group d.) Carbohydrates

Base pairing results because of: a.) Carbon bonding b.) Phosphate bonding c.) Oxygen bonding d.) Hydrogen bonding

Base pairing happens between: a.) adenine and guanine (A-G) b.) cytosine and thymine (C-T) c.) adenine and thymine (A-T) d.) cytosine and adenine (C-A)

DNA Replication Before a cell divides, it duplicates its DNA in a copying process called replication. Before a cell divides, it duplicates its DNA in a copying process called replication. This process ensures that each resulting cell has the same complete set of DNA molecules. This process ensures that each resulting cell has the same complete set of DNA molecules.

The Replication Process the DNA molecule separates into two strands and the DNA molecule separates into two strands and then produces two new complementary strands following the rules of base pairing. then produces two new complementary strands following the rules of base pairing.

The Replication Process Each strand of the double helix of DNA serves as a template, or model, for the new strands.

The Replication Process The two strands of the double helix separate, or “unzip,” allowing two replication forks to form. See video. The two strands of the double helix separate, or “unzip,” allowing two replication forks to form. See video.video

The Replication Process New bases are added following the rule of base pairing: New bases are added following the rule of base pairing: If the base on the old strand is adenine, then thymine is added to the newly forming strand. If the base on the old strand is adenine, then thymine is added to the newly forming strand. Likewise, guanine is always paired to cytosine. Likewise, guanine is always paired to cytosine. See VideoVideo

The Role of Enzymes DNA replication is carried out by a series of enzymes. DNA replication is carried out by a series of enzymes.

Role of Enzymes They first “unzip” a molecule of DNA by breaking the hydrogen bonds between base pairs and unwinding the two strands of the molecule. They first “unzip” a molecule of DNA by breaking the hydrogen bonds between base pairs and unwinding the two strands of the molecule.

The Role of Enzymes The principal enzyme involved in DNA replication is called DNA polymerase. The principal enzyme involved in DNA replication is called DNA polymerase. DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand of DNA. DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand of DNA.

The Role of Enzymes DNA polymerase also “proofreads” each new DNA strand, ensuring that each molecule is a perfect copy of the original. DNA polymerase also “proofreads” each new DNA strand, ensuring that each molecule is a perfect copy of the original. Other video Other videovideo

Because of base pairing in DNA, the percentage of: a.adenine molecules in DNA is about equal to the percentage of guanine molecules. b.thymine molecules in DNA is about equal to the percentage of adenine molecules c.adenine molecules in DNA is much greater than the percentage of thymine molecules. d.cytosine molecules in DNA is much greater than the percentage of guanine molecules.

DNA replication results in two DNA molecules, a. each with two new strands. b. one with two new strands and the other with two original strands. c. each with one new strand and one original strand. d. each with two original strands.

During DNA replication, a DNA strand that has the bases CTAGGT produces a strand with the bases a.TCGAAC. b.GATCCA. c.AGCTTG. d.GAUCCA.