DNA and Epigenetics Flashcards
What is a positive control?
An experimental control group that is not exposed to the experimental treatment but is exposed to some other treatment that is known to produce the desired effect.
For example, if we are designing an experiment to test the efficacy of a new NSAID drug. We can compare our results to a positive control group. In the positive control group, we would have patients take a known NSAID (such as ibuprofen) and compare the results to our experimental group.
What is a negative control?
An experimental group that is subjected to the same conditions as the experimental group but not given the interventional therapy. The negative control group does not expect to see the objective result of the study.
For example, if scientists are studying a new injectable cancer drug; a negative control group may receive the same treatment as the experimental group, but receive a saline injection instead of the pharmaceutical being researched.
What are the primary reasons to include a positive control?
- To make sure you see an effect that SHOULD happen
- Ensure that you don’t have bad materials/techniques
- If you can’t see the positive control effect, even if there should be one in your experimental group you won’t be able to see it
What are the primary reasons to include a negative control?
- To make sure your effect doesn’t ALWAYS happen
- Ensure that you don’t have bad materials/techniques or contamination
- If your negative control also shows the effect, you can’t be sure if your experimental result is a false positive
In Griffith’s experiment, what was the negative control?
Live, nonvirulent bacteria (R Cells)
In Griffith’s experiment, what was the positive control?
The live, virulent strain (S Cells)
What is lateral gene transfer?
The ability for an organism to transfer genetic material to other mature organisms (not parent to offspring). This typically occurs in bacteria and is a major mechanism involved in antiobiotic resistance.
There are three types: transformation, transduction, and cojugation
What are the four macromolecules in biology?
- Carbohydrates
- Lipids
- Proteins
- Nucleic Acids
What are carbohydrates?
Sugars and polymers (long, branched chains) of sugars
* Used as fuel and building material
What are lipids?
Fats, Phospholipids, Steroids
* Used as fuel, cell membrane components, signaling molecules
What are proteins?
- Made up of individual amino acids (20 amino acids)
- Perform a wide range of functions: fuel, transport, cell signaling, enzymes, structural
- The backbone is formed by C-N peptide bonds
- Biologically available in the L (levo) form
What are nucleic acids?
- Made of nucleotides that have a sugar, phosphate group, and nitrogenous base
- DNA and RNA
What are the different types of nucleic acids, where are they found, and what other nitrogenous base will they pair with?
Guanine (G - DNA, RNA)
Adenine (A - DNA, RNA)
Thymine (T -DNA)
Cytosine (C - DNA, RNA)
Uracil (U - RNA)
G-C (three hydrogen bonds)
A-T (two hydrogen bonds)
U-A (RNA, two hydrogen bonds)
How many amino acids are there?
20 main amino acids.
What nitrogenous bases are purines, which are pyramidines?
C,U, and T - pyramidines
A and G - purines
What are the three main types of bonds considered when studying biological systems?
What was the Meselson and Stahl experiment and what did it determine?
Researchers grew E. coli on a medium to incorporate heavy nitrogen (15N) into the DNA of its genome (remember that DNA is composed of nitrogenous base pairs). The researchers then removed the bacteria from the 15N containing medium and transferred it to a growth medium containing normal nitrogen (14N). They found that, even after several replication cycles, the bacterial genome still contained a specific percentage of heavy nitrogen. Thus, proving that DNA is semi-conservative (becuase during replication one strand is conserved - the template strand - while the other is newly assembled)
(https://upload.wikimedia.org/wikipedia/commons/f/fb/Meselson-stahl_experiment_diagram_en.svg)
Why is DNA replication said to be sem-conservative?
During replication (the process of making a new molecule of DNA), one strand of DNA is used as a template, while the complementary strand is newly assembled by the replisome.
Describe the conformation and configuration of DNA
What is DNA’s shape and what are the individual parts?
DNA is double-stranded helix, with each strand running antiparallel with each other (one strand is configured in the 5’ → 3’ direction and the other strand is configured in the 3’ → 5’ direction). DNA is a polymeric molecule composed of many monomer subunits. Each monomer consists of a phosphate group (forming the phosphate backbone), a ribose sugar (each ribose is connected to a phosphate at the #3 and #5 positions, giving us the directional aspect of DNA), and nitrogenous bases (Adenine, Thymine, Guanine, and Cytosine). The phosphate, ribose, and nitrogenous base form one monomeric unit (a nucleic acid).
(https://commons.wikimedia.org/wiki/File:DNA-structure-composition-pt-br.png)
Meselson and Stahl proposed that DNA replication is semi-conservative. If DNA replication was conservative or based on the mosaic model, how would the replication proccess be altered?
Define the terms in bold
If DNA replication were conservative, both strands would serve as a template; so that after replication, the old strand would be 100% the same, while the replicated strand would be 100% new.
The mosaic model of DNA replication, postulates that nucleotides from the original strand will be dispersed throughout the new strand (also known as the dispersive theory of DNA replication).
(https://courses.lumenlearning.com/wm-nmbiology1/chapter/reading-basics-of-dna-replication-2/)
Define epigenetics
Epigenetics considers modication of gene expression by means other than changing the nucleotide sequence of DNA. This modification of gene expression is typically caused my chemical modifications of nucleotides are the structural elements of DNA, to either increase or decrease the expression for a particular gene.
What is methylated DNA? What are the results of DNA methylation?
DNA methylation can either increase or decrease the expression of a gene, and is an epigentic control. If a segment of DNA contains a high concentration of methylation, it is said to be hypermethylated and this gene will be “silent” or underexpressed. If a segment of DNA contains a low concentration of methylation, it is said to be hypomethylated and the gene expression will be increased.
