DNA Structure and Replication Notes PDF

 Nucleic Acids The macromolecule that holds our genetic material (DNA). Contains genes = sections of DNA that serve as the blueprint/instructions for making proteins – Located at certain points on a chromosome Proteins carry out all cellular activity. Tw...

 Nucleic Acids The macromolecule that holds our genetic material (DNA). Contains genes = sections of DNA that serve as the blueprint/instructions for making proteins – Located at certain points on a chromosome Proteins carry out all cellular activity. Two types of nucleic acids: – DNA: deoxyribonucleic acid – RNA: ribonucleic acid  Nucleotides Make up nucleic acids (the monomer) Have three parts: – Sugar Deoxyribose (DNA) Ribose (RNA) – Phosphate – Nitrogen base: Adenine Guanine Cytosine Thymine (DNA only) Uracil (RNA only)  DNA Structure Double helix: like a twisted ladder – Sugar and phosphate form the “sugar phosphate backbone” – Nitrogen bases bond in the middle with weak hydrogen bonds – All other bonds are strong covalent bonds  DNA Structure Nitrogen bases bond only to their complementary base pair with hydrogen bonds – A’s bond with T’s – C’s bond with G’s We call these the “complementary base pairing rules”  RNA Structure Single strand of nucleotides with exposed bases RNA bases bind with DNA bases – A’s bind with U’s – C’s bind with G’s DNA vs. RNA DNA RNA Types of nitrogen A, T, C, G A, U, C, G bases Type of sugar used deoxyribose ribose Shape double helix single strand  Basics of Heredity Chromosomes = tightly coiled strands of DNA – Different organisms have different numbers of chromosomes Ex. Humans have 23 pairs (46 total – 23 from mom and 23 from dad) Ex. Dogs have 37 pairs (74 total – 37 from mom and 37 from dad) Gene = a section of DNA that has instructions to code for a protein – One chromosome can contain thousands of genes linked together! So, genes are pieces/sections of DNA. Chromosomes are long strands of DNA all bunched up.  DNA Replication Background When a cell is ready to divide, it must first copy its DNA. The process of making an identical copy of DNA is called DNA Replication. – DNA  DNA This happens in the nucleus during the S Phase (Synthesis) of Interphase. DNA Replication ensures that each new cell made will have exactly the same DNA as the original cell.  DNA Replication 1. Unzip the DNA. 2. Enzymes help find complementary bases and bind them according to base-pairing rules (A-T and C-G) 3. Two identical DNA molecules are formed, each with an “old” strand and a “new” strand.  DNA Replication It is considered to be Semi-Conservative Replication (because part of the molecule is conserved/saved) Each parent strand is now a template (pattern) that determines the order of the new bases Forms a “complementary” strand to original strand The newly synthesized double helix is a combination of one “old” (or original) and one “new” DNA strand.  Consider… What kinds of mistakes could occur during this process? What would be the implications of these kinds of mistakes happening? – What would be the difference in a mistake in the DNA of a body cell, such as a brain cell, vs. a mistake in the DNA of a germ cell that would eventually make a sperm cell? – What would be the difference in a mistake in a gene vs. in a chromosome?