Labs Flashcards
How many microliters and 1 milliliter?
1 mL = 1000 microliters
In DNA isolation, why is the material mashed up into small pieces?
to provide a greater surface area on which the chemicals can work
What does mechanical disruption do in plant cells?
helps break down cell walls but some plants need additional chemical disruptions to extract the DNA
How was the isolation of the nuclei of wheat germs performed?
- Wheat germ was incubated in a mild detergent (NP-40)
- large debris was filtered out by pouring the sample through cheesecloth
- the liquid is squeezed out, then centrifuged to separate the nuclei and other insoluble material from soluble or lighter cellular organelles
- washed the pellet containing the nuclei to remove insoluble materials
How was the basic protocol of separating nuclear DNA from protein and RNA on the wheat germ performed?
- pellet was resuspended and incubated with a strong detergent and incubated at high temps to lyse the nuclear envelope
- the DNA was separated from the protein in a high salt solution because of their different molecular properties
- by using a high salt solution and alcohol the DNA will precipitate
- some contamination with proteins is expected and some RNA also precipitated
How were the cellular proteins denatured and removed from DNA?
detergent and heat
When a high salt solution is added, why does DNA separate from RNA?
primarily because of the size of DNA, but also because of its double-stranded conformation, and its stability at a more basic pH
How was the refined protocol of separating nuclear DNA from protein and RNA on the wheat germ performed?
- an extra step for protein removal prior to precipitation of DNA occurs
- the protein precipitation solution is added
What is the protein precipitation solution?
a high-salt buffer which affects the solubility of proteins
What is agarose gel electrophoresis used for?
to separate molecules via an electric current. The positively charged molecules will move toward negatively charged electrodes, and negatively charged molecules will move toward positively charged electrodes. DNA and RNA are negatively charged and move toward the positively charged electrode
What factor affects the rate of migration for molecules in an electrophoresis?
- shape
- charge-to-mass ratio
- size
What is the purpose of SYBR Safe?
bind to DNA and enables visualization of DNA bands under UV light
What is the purpose of TBE buffer in the gel electrophoresis?
provides ions that carry current and maintain
the pH at a relatively constant value
What are the basic steps of PCR?
- Denature the double-stranded DNA template (high temp)
- Anneal (base-pairing) of designed DNA primers to sequence to be
amplified (low temp) - Synthesis (extension) of DNA using heat stable DNA polymerase
(Taq) (med temp)
What does one cycle of PCR result in?
the amount of DNA is doubled
What does the PCR buffer do?
Maintains pH for Taq polymerase to function, increase yield and efficiency of reaction
What do the primers do during a PCR?
Complementary to 3’ end of DNA and anneals to DNA template
What does MgCl2 do during PCR?
Provide divalent cations required for activity of DNA polymerases
what is the role of dNTPs during a PCR?
Contains dGTP, dCTP, dATP, dTTP nucleotides that can be incorporated into the growing DNA strand
How are genes studied?
We sequence genes to convert DNA into letter codes (A, C, T, G)
which we can then study.
* Sequenced genes can then be stored in repositories (e.g.
GenBank) where they can be studied by other scientists.
What are bioinformatic tools used for?
- Compare nucleotide sequences and look for additions,
deletions, or substitutions. - Translate nucleotide sequences into amino acid sequences to
better understand protein structure and function
How are genes compared to one another?
BLAST to search a sequence database (GenBank) for matches to your sequence of interest
How does BLAST access the quality of the match?
- Percent coverage: percent of your sequence that overlaps with a sequence in the database
- Percent identity: percent of base pairs that are the same between your sequence with a sequence in the database
What is PCR?
a method that makes it possible to generate millions of copies of the specific DNA sequence of interest
What is BLASTN used for?
used to compare a nucleotide sequence with a nucleotide database
What is BLASTP used for?
used to compare a protein sequence with a database of protein sequences
What is Clustal Omega used for?
for carrying out multiple sequence alignment, which generates the alignment between three or more sequences