AP Biology Chapter 16 Notes

Molecular Basis of Inheritance

What you need to know…

  • The structure of ______.
  • The major steps of ______.
  • The difference between ______, ______, and ______.
  • How DNA is packaged into a ______.

Concept 16.1: DNA is the genetic material

•Important Scientists –

–Alfred Hershey and Martha Chase – Next Slides - ______is the genetic material

–James Watson and Francis Crick – structure of DNA

–Rosalind Franklin – next slides - produced a picture of the DNA molecule using ______crystallography; discovered DNA is a ______

3 Deductions by Watson and Crick

•DNA = ______ (twisted ladder). Sides are made up of sugar and phosphate backbones and rungs are made up of nitrogenous base pairs.

•Nitrogenous bases are ______(A), ______(T), ______(G), and ______(C).

•Strands are ______ – left side runs 5’-3’ while opposite strand runs 3’-5’.

Concept 16.2: Many proteins work together in DNA replication and repair

  • Since the two strands of DNA are ______, each strand acts as a template for building a new strand in replication
  • In DNA ______, the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules
  • It is considered ______replication
  • ______ – making of DNA from existing DNA strands
  • begins at special sites called ______, where the two DNA strands are separated, opening up a replication “bubble”
  • Replication Bubble formed by ______ that unwinds the DNA. Replication continues in both directions along strand until copied.
  • DNA ______ add nucleotides to strand at replication fork.
  • DNA Polymerase works in a 5’-3’ direction (______strand) matching bases.
  • ______strand (3’-5’) is copied in series of segments.
  • Lagging strand segment pieces are called ______fragments – tied together with DNA ______.
  • The initial nucleotide strand is a short RNA ______
  • An enzyme called ______can start an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template
  • The primer is short (5–10 nucleotides long), and the 3 end serves as the starting point for the new DNA strand
  • Label the Picture: Replication of Leading Strand
  • Replication of the Lagging Strand
  • DNA polymerase must work in the direction ______from the replication fork
  • The lagging strand is synthesized as a series of segments called ______fragments, which are joined together by DNA ______
  • See the Handout Replication of the Lagging Strand
  • Proofreading and Repairing DNA
  • DNA ______proofread newly made DNA, replacing any incorrect nucleotides
  • In ______repair of DNA, repair enzymes correct errors in base pairing
  • DNA can be damaged by ______, ______emissions, ______, ______, and certain molecules (in cigarette smoke for example)
  • In nucleotide excision repair, a ______cuts out and replaces damaged stretches of DNA
  • Replicating the Ends of DNA Molecules
  • Limitations of DNA polymerase create problems for the linear DNA of eukaryotic chromosomes
  • The usual replication machinery provides no way to complete the 5 ends, so repeated rounds of replication produce ______DNA molecules
  • Eukaryotic chromosomal DNA molecules have at their ends nucleotide sequences called ______- do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules
  • An enzyme called ______catalyzes the lengthening of telomeres in germ cells

Concept 16.3 A chromosome consists of a DNA molecule packed together with proteins

  • The bacterial chromosome is a double-stranded, ______DNA molecule associated with a small amount of protein
  • Eukaryotic chromosomes have ______DNA molecules associated with a large amount of protein
  • In a bacterium, the DNA is “supercoiled” and found in a region of the cell called the ______
  • ______is a complex of DNA and protein, and is found in the nucleus of eukaryotic cells
  • ______are proteins that are responsible for the first level of DNA packing in chromatin

You should be able to:

  1. Describe the contributions of the following people: Griffith; Avery, McCary, and MacLeod; Hershey and Chase; Chargaff; Watson and Crick; Franklin; Meselson and Stahl
  2. Describe the structure of DNA
  3. Describe the process of DNA replication; include the following terms: antiparallel structure, DNA polymerase, leading strand, lagging strand, Okazaki fragments, DNA ligase, primer, primase, helicase, topoisomerase, single-strand binding proteins
  4. Describe the function of telomeres
  5. Compare a bacterial chromosome and a eukaryotic chromosome