Lecture 25Outline of Last Lecture1. Pleiotropy: discuss how a single gene can affect many features of the organism.2. Discuss the the inheritance of X-linked genes in mammals. 3. Discuss what it means to be hemizygous, and what is means to be a mosaic. What is a Barr Body, and what is dosage compensation?4. Define linkage, and relate it to specific events in meiosis.5. Show how data from a test cross involving alleles of two loci (‘two point test cross’) can be used to distinguish between independent assortment and linkage.6. Know how to calculate allele frequency using the Hardy-Weinberg equation.7. Explain how prenatal testing, carrier screening, and newborn screening can be used to detect genetic conditions before and after birth. Outline of Current Lecture1) Summarize the evidence that accumulated during the 1940s and 1950s demonstrating that DNA is the genetic material.2) Illustrate how the two strands of DNA are oriented with respect to each other (antiparallel).3) State the base-pairing rules for DNA, as determined by Chargaff and coworkers, and describe how complementary bases bind to each other.4) Sketch how nucleotide subunits link together to form a single DNA strand. Summarize how DNA replicates, focusing particularly on the different enzymes in the process.I. DNA Evidence StoryThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st EditionThe story of how DNA took its place as genetic material goes something like this:Frederick Griffith finds a substance in dead bacteria that live bacteria take in and transform themselves with. Later it is chemically identified as DNA. People start to speculate that DNA is responsible for genetic transformations. Later, it is found that DNA is not a protein through seeing what a virus injects in a cell is DNA, not proteins. Rosalind Franklin produces an X ray diffraction image of DNA. Watson and Crick use this to formulate what they believe is the DNA structure. The model they proposed is the DNA Double Helix structure. II. DNA Strand OrientationThe way the DNA strands are set up is that the nitrogenous bases are only able to be on the right side of the strand. Each strand has a 5’ direction and a 3’ direction. In order for these stands to connect bases they must point inwards at each other, but the bases are stuck on the right side. Therefore, the secondary strand is inverted upside down so that where the 1st strand is pointed 5’ to 3’, the 2nd one is points 3’ to 5’. This way, the bases connect to each other and form the double helix shape.III. Base Pair RulingThis ruling states basically:- A connects to T, G connects to C. - The complementary nitrogenous bases are held together by hydrogen bonds.- The purine bases connect to pyrimidine bases.IV. DNA Replication ProcessNucleotides are bonded to the ends of the 3’ end of the strand. Specifically, the 5’ phosphate group of one nucleotide is covalently bound by condensation synthesis to the 3’ OH of the next nucleotide, creating a Phosphodiester bond. The process goes like this: These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st EditionDNA Helicase breaks the hydrogen bonds between the pyramidines and the purines and breaks apart thetwo individual strands of DNA. DNA polymerase adds a few nucleotides to the end of a free 3’ chain. The DNA polymerase on the leading strand proceeds to synthesize DNA in the 5’ to 3’ direction. While the leading strand continually synthesizes, the lagging strand goes through a process. In the lagging strand, DNA polymerase adds new deoxyribonucleotides to an unbound 3’ OH. It does this by having RNA primase attaching to the DNA and synthesizes a little RNA primer. DNA polymerase III adds deoxyribonucleotides to the end of this little RNA primer. DNA polymerase I replaces the DNA polymerase III and replaces the RNA with DNA. Lastly, the enzyme DNA ligase forms a phosphodiester bond between the 3’ OH of the growing strand and the 5’ phosphate that’s in front of it.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st