Midterm 1 Review Notes BIOL 3110 PDF
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These review notes cover topics in biology, such as the experiments of Paul Berg and Friedrich Miescher. Topics also include important breakthroughs in genetics and laws of inheritance by Gregor Mendel.
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Midterm 1 Review Notes ADDED TO ANKI Week 1: Paul Berg’s Experiment (1971) Invention of Recombinant DNA technology through gene splicing Spliced the DNA of the Bacterial Virus Lambda into the DNA of the Monkey Simian Virus by: 1. Cutting both DN...
Midterm 1 Review Notes ADDED TO ANKI Week 1: Paul Berg’s Experiment (1971) Invention of Recombinant DNA technology through gene splicing Spliced the DNA of the Bacterial Virus Lambda into the DNA of the Monkey Simian Virus by: 1. Cutting both DNA at EcoRI enzyme restriction sites using the EcoRI enzyme 2. Ligated the new DNA into the old, returning to a loop 3. Now the DNA could express genes from different sources (Recombinant DNA) - S IGNIFICANCE: Invented Recombinant DNA technologyto be able to insert foreign genes into a virus, causing it to become a vector that could carry this DNA into other cells/a host. - WE COULD START MANIPULATING GENES BC OF HIM Mendel’s Laws of Inheritance (1866): 1. Law of Independent Assortment: Each trait is controlled by specific factors that operate independently from another, and are transmitted independently as each exists on a different chromosome. 2. Law of Independent Segregation: Each characteristic exists in alternate forms (ie. Tall vs. Short) These characteristics are controlled by a pair of alleles, and one allele is transmitted from each parent to the offspring The pairs segregate in germ cells (gamete formation), and recombine during reproduction 3. Law of Dominance For each characteristic, one allele is dominant and one allele is recessive The dominant alleles appear more often, in a 3:1 ratio Friedrich Miescher (1869): Leukocytes: Studied leukocytes from pus on surgical bandages from soldiers to “isolate nuclein” by purification. D NA precipitated in the alkaline solution as it disrupts the structure of the cell membrane, denaturing both the protein and the DNA. This ultimately lyses the cell content, but the DNA denaturation process is reversible. So it precipitates. Named the substance that he found within the nuclei “nuclein” According to Miescher’s Leukocyte DNA purification research, he determined that: ○ Nuclein doesn’t contain any proteins since it doesn’t contain any sulfur (which we know is obviously false, just determined due to the knowledge of sulfur containing a.a. at the time) ○ Nuclein contains large amounts of phosphorous Salmon Sperm DNA Purification: Did this as leukocytes had small nuclei compared to cytoplasmic content → salmon sperm contained mostly nuclei and were easily purified. Found that this nuclein contained mostly C, N, H, O, and Phosphorous atoms → as DNA does contain this all. Criteria for the Molecule/Carrier of Inheritance: 1. Must be passed on from one generation to the next 2. Must be duplicate and equally divided when the cell divides 3. Must be physically stable → DNA wasn’t considered to be the carrier of genetic information in Miescher’s time because at the time, there was no connection between DNA and being a carrier of genetic information. Just the knowledge of 20 amino acids in a protein, and it was considered to be more information rich than the 4 bases DNA had. So it was mistaken that proteins were the molecule of inheritance. Walther Flemming (Germany) Improved the resolution of the microscope, and used abasophilic dyeto stain the material inside of the cell nucleus → CALLED IT CHROMATIN He then used this dye to stain salamander embryos going through cell division → Chromatin collected into thread-like structures, CALLED THEM CHROMOSOMES Coined the term mitosis to describe behaviour of chromosomes during cell division: ○ Found that each daughter cell contained a set of chromosomes identical to the parent cell → WHICH LED TO DNA DISCOVERY AS THE MOLECULE OF INHERITANCE AS FITS THE CRITERIA OF DUPLICATION AND EQUAL DIVISION WHEN CELL DIVIDES, PASSING FROM ONE GENERATION TO THE NEXT AND BEING ULTIMATELY PHYSICALLY STABLE! Thomas Morgan (USA): S tudied fruit flies as they reproduce really fast Found that the results in the trait of eye colour did not match Mendel’s Law of Dominance, the ratio being way off. Also found that Mendel’s law of independent assortment was wrong, as the introduction of genetic linkage meant that the genes that are close together are often inherited together. Found that all white-eyed flies were male, proposed that their sex and eye colour were associated in fruit flies. ○ PROPOSED THAT SEX COULD ALSO PLAY A ROLE IN INHERITANCE → introduced sex-linked genes + concept of genetic linkage (genes that are close together on the chromosomes are often inherited together). Herman Muller (USA): Worked with Morgan to use X-Rays to induce mutations in the fruit fly genome (1927) Was the first one to determine that genes can be inherited ○ Found that genes can be mutated by chemical/radiological means, and that these mutated genes can be passed onto offspring. Beadle & Tatum’s Experiment: The model organism of Neurospora (Bread spores) was chosen for the experiment because they exist as haploid organisms, which can rapidly mate with the mutated type to produce ascospores (now there’s 2 copies of the mutant spore due to mating with the opposite mating type, makes it 2n). → can undergo meiosis, then further cell division to go back to 1n. Hypothesis: test the function of a gene, proposed that each gene is responsible for making a different protein, most of which function as enzymes. Experimental design: used a forward genetic screening model to isolate a specific gene from the phenotype, to see what the function of this gene is. → Introduced a mutation through random mutagenesis ○ Isolated the mutant phenotype by trying to grow in the minimum medium → knew that wildtype spores can synthesize all AAs, so they can grow on complete and even minimal mediums (without AAs) - But the mutation in the mutant spores cause disruptions in the AA biosynthesis pathways and don’t end up growing on minimal mediums. Observed that this gene that was mutated is responsible for synthesizing a specific amino acid to allow spore growth, supporting their hypothesis. This was notable because they noted that a gene codes for proteins. ompare and contrast Forward and Reverse genetic screens. Explain why Beadle and C Tatum’s experiment is a type of Forward genetic screen. Forward genetic screening: Finding the gene from the phenotype (phenotype → gene) Random mutagenesis Isolation of a mutant phenotype, and studying where the gene passes the mutant phenotype. Figures it out through the change in the phenotype, identifying responsible genes. Reverse: Finding the phenotype from the gene (gene → phenotype) Targeted mutagenesis Known gene is mutated to observe which phenotype it governs. (observing phenotypic changes) Beadle and Tatum’s Forward genetic screening: Mutated the genome, and screened for a specific phenotype after crossing the mutagenized conidia with the wildtype to produce the ascospores ○ (lost the ability to synthesize a specific amino acid) efine the one gene:one enzyme (or one protein) hypothesis and provide an example of D an exception: Known as the precursor of the central dogma Each gene in an organism is responsible for making a different protein, most of which function as enzymes ○ The exception is that not all genes code for enzymes, some code of RNA molecules like tRNAs (transfer RNAs) and rRNAs (Ribosomal RNAs) 1. Week 2: F or Griffith’s experiment, interpret the observation and conclusion of the experiment. Define transformation and describe the molecular basis and the principle of transformation. Explain the significance of Griffith’s research. [Comprehension, Analysis] G riffith was a microbiologist, studied the pathology of bacteria that causes pneumonia ○ R strain doesn’t cause pneumonia - can be recognized by immune cells that clear it out ○ S strain causes pneumonia - can’t be recognized by immune cells due to its polysaccharide coat, immune cells can’t attack it. Transformation → DNA introduced into a bacterial cell from its environment, incorporating the DNA into its own gene. (uptake of foreign DNA from the environment into the bacterial genome) Discovered transformation by mixing heat-killed S cells and living R cells, as the R cells up took the DNA → Suggested that heritable traits can be exchanged between bacterial strains T his research was significant because he concluded/proposed that there was an exchange of genetic information between the R strain and the S strain (non-virulent R strain transformed into virulent S strain) F or Avery, Macleod and McCarty’s experiment, explain the hypothesis of the experiment, the experimental design, and interpret the observation and conclusion of the experiment. Explain the significance of Avery, Macleod and McCarty’s research. [Comprehension, Analysis] Experimented to see what component of the dead S strain transformed the R bacteria Hypothesis: If DNA was the molecule of inheritance, it would be the molecule being passed from the heat-killed S cells to the R cells. Experimental design: used the elimination approach to remove proteins with protease, then remove RNA with ribonuclease, then DNA with deoxyribonuclease to see if transformation occurs without each factor. Observed that no transformation only occurred when DNA was not present Concluded that DNA was the molecule that caused the transformation! Super significant as they figured out that DNA was the molecule that was passed to the bacteria. F or Hershey and Chase’s blender experiment, explain the hypothesis of the experiment, the experimental design, and interpret the observation and conclusion of the experiment. Explain the significance of Hershey and Chase’s research. State why it is often referred to as a blender experiment. [Comprehension, Analysis] Hypothesis: Wanted to find out what the genetic material in the bacteriophage was, DNA or Protein? ○ Phage injects Protein or DNA into e.coli? Experimental design: used radioactive 35S and 32P to label the protein shell and the DNA inside of the bacteriophage, bacteriophage inserts it into the e. coli, blended it to remove the bacteriophage protein coats from the surface of the e.coli and see what goes into the e. Coli Observed that the phage coats remained in the media, containing 80% of the 35S label, and the infected bacteria contained 70% of the 32P label (in the pellet) Also observed that the progeny phages contain 30% of 32P label and
