Do Now: Take out a piece of paper What is an example of a nucleic acid? DNA What are the building blocks of nucleic acids? Nucleotides What are the four nitrogenous bases in DNA? (You can write just letters) Adenine, Thymine, Guanine, Cytosine Who were the two scientists that discovered the structure of DNA and what was the model called? Watson and Crick; the double-helix model Fill in the complimentary base pairs: A – T – T – G – C – A – T – C – C – C – G
AIM: How is DNA copied before Mitosis? In this picture, two new strands are copied from the two old strands
Remember… DNA - the genetic material - is a DOUBLE HELIX composed of: Two strands Sugar-Phosphate backbone (Ribose w/o Oxygen, Phosphate) Nitrogenous bases in the middle (A-T, G-C…always)
Regents Review If 15% of a DNA sample is made up of thymine, T, what percentage of the sample is made up of cytosine, C? 15% 35% 70% 85%
The two strands run in opposite directions The two strands run “ANTI-PARALLELL” to each other This allows the bases to be hydrogen bonded in the middle
Anti-parallel Beginning End Beginning End
Regents Review A portion of a molecule is shown in the diagram below. Which statement best describes the main function of this type of molecule? It is a structural part of the cell wall. It stores energy for metabolic processes. It determines what traits may be inherited. It transports materials across the cell membrane.
The Replication Process Before a cell divides, it duplicates its DNA – REPLICATION This process ensures daughter cells have a complete set of DNA
DNA Replication During Replication: DNA strands separate – get “unzipped” Each strand serves as a template New bases are added to the two old strands Result: Two DNA identical DNA molecules – each molecule has one old strand and one new strand.
Enzymes involved in Replication Helicase Unzips the DNA DNA Polymerase Joins individual nucleotides to the new strand of DNA Proofreads new strand to ensure correct pairing
Replication in Prokaryotes vs. Eukaryotes Prokaryotes Starts from a single point Usually have one circular piece of DNA (one chromosome) No nucleus! Occurs in cytoplasm! Eukaryotes Many different starting points Much more DNA Packed into chromosomes In the nucleus
Split up into pairs Use test taking strategies to work on regents questions
Regents Review When DNA separates into two strands, the DNA would most likely be directly involved in replication fertilization differentiation evolution
Regents Review Which nuclear process is represented below? recombination fertilization replication mutation
Regents Review A change in the base subunit sequence during DNA replication can result in variation within an organism rapid evolution of an organism synthesis of antigens to protect the cell recombination of genes within the cell
Regents Review A characteristic of a DNA molecule that is not characteristic of a protein molecule is that the DNA molecule can replicate itself can be very large is found in nuclei is composed of subunits