BIOLOGY 111 1st Edition Lecture 24 Outline of Last Lecture I. Gene regulationII. OperonsIII. Negative and Positive ControlIV. Chromatin level regulationV. Protein Stability Current LectureI. Polymerase chain reactionII. Short tandem repeatsIII. Gel electrophoresis IV. Transgenic animals and plantsV. Stem Cells Outline of Current Lecture - PCR (polymerase chain reaction)o This is a laboratory technique that is used to replicate (to amplify, make more of) a specific DNA segment o It was developed by Kary Mullins in the ‘80s, winning nobel prize in ‘03o It is especially useful in forensics when DNA traces are found at a crime scene and lab tests on the DNA are needed to solve the crime o It involves adding nucleotides with the help of polymerase and primerso During each round of PCR, the two nucleotide strands separate, and each strand serves as a template for the addition of nucleotides.  Heating separates the strands And the Cooling allows the DNA polymerase to pair new nucleotides with the original template strand  PCR makes twice as much for every cycle, easily yielding billions of copies just after a couple of cycles - Short Tandem Repeats o These are usually found in the non-coding region of DNA o We all have STRs in the same place along our chromosomes, but it is the length of our STRs that varies from person to person 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.o In the 23 pairs of chromosomes a human has, we have identified 15 STR regions- Gel Electrophoresis o A laboratory technique that separates STRs according to their length o The DNA is placed into the wells of a gel that is then set into a buffer solution. An electrical current pulls the negatively charged DNA from the negative end to the positive end.  Smaller DNA fragments travel further than larger fragments Larger fragments will be found more toward the top of the gelo In a gel electrophoresis of an STR for paternity (comparing a childs STR to that of the mother and the father) If the child inherited an STR band that both the mother and the father contained, then the single band for the child will be broader If the child inherited an STR band from only the mother or the father but not both, the child will have a single band that is more narrow - Transgenic animals and plantso Transgenic animals are made by introducing genes from one species into the genome of another animalo Genetic engineering in plants has been used to transfer many useful genes including those for herbicide resistance, increased resistance to pests and salinity, and improved nutritional value of crops - Stem cells o Stem cells are immature cells that can divide and differentiate into specialized cell types Adult (somatic) stem cells – differentiate only into a limited number of cell types (multipotent – very specific) Embryonic stem cells (ESCs) ৹ Cells dividing during early development (blastocyte stage)৹ Those that can differentiate into nearly any cell type (pluripotent– less specific and more manipulative)৹ Very early embryonic stem cells that can differentiate into any cell type (totipotent – can be used for anything)o Sources of stem cells  Discarded human embryo from fertility and abortion clinics  Cloning – nucleus of haploid human egg cell is replaced with diploid nucleus of somatic cells which forms an embryo that can be cultured (SCNT – somatic cell nuclear transfer) A mature stem cell that is genetically manipulated to become an embryonic-like stem cell (induced pluripotent stem