Lab Practical Exam #3 Flashcards
How many strands is DNA?
Two
What are the nitrogenous bases of DNA
Adenine, cytosine, guanine, and thymine
What type of sugar is in DNA?
deoxyribose
Where is DNA found?
Nucleus of eukaryotic cells, nucleoid in prokaryotic cells
What makes up a single nucleotide?
Phosphate, deoxyribose sugar, and nitrogenous base
Where does DNA replication take place?
Nucleus of eukaryotic cells, nucleoid in prokaryotic cells
What part of the cell cycle does DNA replication happen?
S (synthesis) phase
Chromatin
a complex of DNA and proteins that forms chromosomes within the nucleus/nucleoid
Centrosome
an organelle that is a microtubule which organizes (in cell division)
Centromere
Located in central area of chromosome; links a pair of sister chromatids together during cell division
A string of nucleotides would eventually code for a
amino acid/polypeptide chain
Chromatid
Half of a chromosome; ensures each new daughter cell has the correct complement of DNA at the end of cell division
What is meant by “double helix”?
A DNA molecule is made up of two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape.
What are the steps of the DNA isolation that was used in the simulation?
Place test tube on ice;
transfer strawberry filtrate with pipette to test tube;
in a graduated cylinder, dissolve a spoonful of meat tenderizer into distilled water;
add meat tenderizer solution to strawberry filtrate and let it react for 10 minutes;
use pipette to add ice cold 95% ethanol along inside of tube to precipitate DNA;
with the test tube in the rack, spool precipitated DNA onto glass rod.
What was the glass rod used for? What is spooling? What direction should spooling be done in?
The glass rod was used to spool. Spooling is a method of isolating strands of DNA from a solution. Spooling is done slowly in a constant motion.
What was the ethanol used for? Why should ethanol be added slowly?
Ethanol was used because DNA is not soluble in it, therefore the DNA will precipitate.
What was the DNA isolated from in the simulation?
The DNA isolated was from strawberry filtrate.
What was the meat tenderizer used for?
To digest associated proteins that bind the DNA.
What was the detergent used for?
Detergent emulsifies cell and nuclear membranes of cells. The detergent disrupts phospholipid bilayers.
What is homogenization and when was it done in the isolation process?
Homogenization is grinding a substance. This was done first to create the strawberry filtrate.
Why were the tubes and reagents kept in an ice bath during isolation?
Cold temperature stabilizes DNA.
What does the isolated DNA look like in the tube?
Long, thin, white mucus-like strands.
Transcription: What molecule is produced by this process?
RNA
Transcription: Where in the cell does transcription take place?
Nucleus
Transcription: Given a sequence of DNA bases, be able to transcribe the code into mRNA.
A-U & G-C
Translation: What molecule is produced by this process?
Proteins
Translation: Where does translation take place?
Ribosomes in the cytoplasm
Translation: What are the three types of RNA and their functions?
mRNA: carry the coding sequences for protein synthesis;
rRNA: form the core of a cell’s ribosomes (where protein synthesis takes place);
tRNA: carry amino acids to the ribosomes in protein synthesis
Translation: Which type of RNA possesses codons?
mRNA
Translation: Which type of RNA possesses anticodons?
tRNA
Translation: Which type of RNA possesses the amino acid?
tRNA
Translation: What do codons code for? Can one codon code for more than one amino acid?
Code for amino acids.
No, one codon codes for one amino acid.
Translation: Given an mRNA codon, determine the anticodon on the tRNA molecule.
A-U & G-C
Translation: Given mRNA codons, determine the amino acid sequence in a polypeptide.
ez
What is the purpose of gel electrophoresis? What things can it be used for?
Gel electrophoresis separates DNA samples by size. This indicates different genotypes associated with a genetic condition.
Gel electrophoresis separates DNA fragments on the basis of . .
size and charge
Should the positive electrode be attached closest to or farthest from the wells?
farthest
What is the charge on the DNA samples?
Negative
Why does DNA flow toward the positive side of the chamber?
DNA is negatively charged.
How are the DNA samples added to the wells in the gel?
A micropipette is used.
What is agarose?
A gelling agent used to visualize DNA fragments.
Would a small fragment move faster or slower in a gel?
Faster
Why do the samples move?
An electric current is applied to the gel so one end of the gel has a positive and the other a negative charge, so samples move towards the opposite charge.
Before pouring the gel into the casting tray what should you do to the open end of the tray?
Mount masking tape in both ends of the gel casting tray and then add gel comb to create wells for loading DNA samples.
What is bromothymol blue used for?
To illuminate DNA so the DNA banding patter can be visualized.
Do the samples move through the gel or through the buffer?
Through the gel
What voltage should the gel be run at? Is this supposed to be a high or low number?
Higher voltage (100-135 V) for fast separation of small DNA fragments and lower voltage (50-75 V) for clear separation of large DNA fragments. The lab used 70 V.
What is nondisjunction and what effect can it have on a cell?
It is the failure for a chromosome to separate and can lead to aneuploidy (daughter cells with abnormal amount of chromosomes).
In what process does nondisjunction take place?
Anaphase of mitosis, meiosis I, or meiosis II.
What is an aneuploidy?
An abnormal amount of chromosomes in a cell or organism.
Differentiate between monosomy and trisomy
Monosomy: one chromosome out of two is present, trisomy: one chromosome in addition to two.
Turner syndrome
(sex chromosome disorder)
Monosomy: one X chromosome instead of two
Female
Triple-X (Poly-X)
(sex chromosome disorder)
Trisomy: An extra X chromosome to XX
Female
Klinefelter Syndrome
(sex chromosome disorder)
Trisomy: An extra X chromosome to XY
Male
Jacob Syndrome
(sex chromosome disorder)
Trisomy: An extra Y chromosome to XY
Male
Down syndrome
(autosomal disorder)
Trisomy: An extra X chromosome to XY on chromosome 21
Male and female
