Exam 3 (Final) Flashcards
In PCR, how many strands are copied?
Both strands
Describe the general process of PCR.
1) Heat – denature template DNA and primers
2) Cool – anneal primers
3) Heat – DNA polymerase synthesizes new DNA
Primers anneal best at ______(hot/cool) temperature.
cool
DNA polymerases work best at ____(hot/cool) temperatures.
hot
What end of the DNA primer has a component that allows nucleotides to be added to it? And what is the component?
3’-OH
What does it mean if a vector or cell is “competent”?
It is able to take up foreign DNA
Name three important components of vectors.
Origin of replication
Enzyme cut sites
Marker sequences
When screening cultures (with the method that uses penicillin and B-gal) what color colonies are you looking for? What makes them that color?
Looking for WHITE colonies; made white when the insert is inserted into B-gal gene (turning off its expression of blue)
When screening colonies, what special components are within the VECTOR and the INSERT that help in the screening process?
Vector – contains penicillin resistance and lacZ gene (makes cultures blue)
Insert – disrupts the lacZ gene, making that colony white
If a colony grows blue, you know that it contains WHAT?
If a colony grows white, you know that it contains WHAT?
If a colony does not grow at all, you know that it contains WHAT?
If blue: contains vector but NOT insert
If white: contains vector and insert
If does not grow: contains neither
If you want to determine fragment size, you should use WHAT?
Gel electrophoresis
What does RFLP stand for? What is it? What can it show you?
Restriction Fragment Length Polymorphism; when two individuals show different patterns of band sized after enzyme digestion; Can show if there is a mutation in a organism, because the restriction enzymes will cut it differently
Southern Blotting allows you to see WHAT?
If DNA contains a desired sequence; can also be used to compare DNA sequences across species/organisms
In Southern Blotting, do you FULLY or PARTIALLY digest the DNA?
Fully
In Southern Blotting, what kind of probe is typically used?
radioactive probe that expresses as a dark band when put against an x-ray film
Differentiate between a genomic library and a cDNA library.
genomic library: contains full DNA
cDNA library: contains just isolated mRNA sequences (to see actively translating proteins)
What roll does reverse transcriptions play in the creation of THIS SPECIFIC TYPE OF genomic library?
In a cDNA library, reverse transcription is used to turn mRNA into cDNA (complimentary DNA)
When making a genomic or cDNA library, do you want FULL or PARTIAL digestion by enzymes? Why?
partial because you must use it to reconstruct the genome, using overlapping segments as your guide
_______ can be used to scan genomic/cDNA libraries.
Southern Blotting
What does FISH stand for? What is it?
Fluorescence in situ hybridization; used to see expression in specific locations (in site) in the body/tissue/organ/etc
Dideoxy sequencing is also called WHAT?
Sanger Sequencing
What is Dideoxy/Sanger Sequencing?
Using fluorescently labeled dideoxyribose (as well as normal deoxyribose), DNA elongation is cut short at different locations as it is replicated (in a similar manner to PCR, but only with ONE strand, because you only use a primer for one strand); end of nucleotide is labeled with a color; Perform gel electrophoresis and read out the sequence in order (from shortest segment to longest)
What is it about dideoxyribose that makes it useful in sequencing DNA?
Missing an O on the 3’-OH (making it a 3’-H); This makes it unable to bind to the next nucleotide, halting elongation
What is special about NEXT GENERATION SEQUENCING?
Relies on simultaneous sequencing of millions of partially digested fragments and then a massive reordering by looking at overlapping sequences
Genomic and cDNA libraries hold all the fragmented DNA in WHAT?
bacterial vectors
How do you read a microarray based assay that compares DNA from two different organisms?
cDNA from each organism is labeled with a different fluorescent color;
Your microarray “chip” has a bunch of different wells that contain complimentary binding sequences for a variety of known sequences; cDNA from the two organisms compete to bind with these sequences; if a well contains sequences that bind to cDNA in both organisms, the well will light up with a color that is in between the two colors you used to label your cDNA in each organism
What does PCR stand for?
Polymerase Chain Reaction
What does the ampR gene encode for?
enzyme beta-lactamase, which breaks down penicillin, enabling the bacterium to resist it
What are two types of NEXT GENERATION SEQUENCING?
Pyrosequencing and Illuminasequencing
What happens in PYROSEQUENCING?
- DNA to be sequenced in partially digested and made single stranded
- Each fragment is attached to a bead and placed in an individual well (similar to microarray)
- Each fragment is individually amplified within its well
- Tray is sequentially flushed with a particular type of deoxynucleotide triphosphate (A, T, C, or G), so that strands are synthesized in a controlled manner
- During each incorporation, 2 phosphates are cleaved off and provide the energy to generate a small flash of light
- All of this information can be integrated to sequence the DNA
What happens in ILLUMINA SEQUENCING?
- each base is assigned a uniquely colored fluor attached to a “stopper molecule” that prevents elongation until it is removed
- After each incorporation (similar to how it is done sequentially in pyrosequencing), a chemical reaction removes the fluor and “stopper molecule” and reads the residual flash of light, for which the color indicates the incorporated nucleotide
- Process repeated until all fragments are sequenced
Define germline mutation.
Present in either (or both) the sperm and the egg that made the individual, therefore present in every cell the individual has
Define somatic mutation.
Arise after fertilization, during division/replication/etc, thus only present in a subset of the individual’s cells
Somatic mutations are passes down to how many of its descendents?
1/4th
What is a CONDITIONAL MUTATION?
Only arise under certain conditions
A food allergy is an example of a _________ mutation.
Conditional
How can somatic mutations be passed down to offspring?
If a mutation exists in the sex cells, it can be packaged into a gamete. This is a germline mutation from the perspective of the offspring.
How can strand slippage result in addition or deletion of nucleotides?
Newly synthesized strand loops out –> Addition
Template strand loops out –> Deletion
Explain how repeated sequences can cause inversions and deletions.
Unequal crossovers results in a deletion on one strand and an addition on the other.
Define TRANSITION vs TRANSVERSION
Transition: purine-purine or pyrimidine-pyrimidine substitution
Transversion: purine-pyrimidine substitution (or vice versa)
Define MISSENSE vs NONSENSE mutation.
Missense: causes one amino acid to replace another
Nonsense: creates a stop codon at site of mutation
Define NEUTRAL mutation.
Changes amino acid content of protein but has no function consequence
Define SYNONYMOUS/SILENT mutation.
Does not change amino acid content
Define BENIGN POLYMORPHISM.
No change in protein activity.
How can synonymous mutations alter splicing?
- Can mutate within in the intron or exon
- Almost all human introns begin with GT; so if C –> T mutation changes GC –> GT, the spliceosome may splice before GT
Most human introns begin with ____.
GT
When to trinucleotide repeats most often expand?
during cell replication/division
Define NON-replicative transposition vs replicative transposition.
Non-replicative: “cut and paste”
Replicative: “copy and paste”
Describe the structure of a transposable element.
Terminal Inverted repeats flank the transposon.
What repeat sequence in generated after the transposable element inserts itself?
The flanking direct repeats
Do the flanking direct repeats come from the target DNA or the transposable element?
target DNA; they are generated from the staggered cuts that are made when the transposable element inserts itself
What is the role of transposase?
makes short, single-stranded overhangs on target DNA that are complimentary to each other; replicated to become the flanking direct repeats
What is a retrotransposon?
Transpose through an RNA intermediate using reverse transcription (more common in eukaryotes)
Describe the methods of a retrotransposon.
1) Retrotransposon DNA transcribed into RNA (DNA transposon is never removed from its sequence)
2) RNA undergoes reverse transcription to produce double-stranded DNA
3) Insertion proceeds as normal
Is retrotransposition a form of replicative or non-replicative transposition?
replicative, as the original DNA element is never removed from its location
Pigment production in grapes in controlled by a _________ element.
RETROtransposable
In relation to pigment production in grapes, when do the following colors come about?
BLACK
WHITE
RED
Black: fully functional gene
White: retrotransposon inserted into pigment gene
Red: retrotransposon moves out of the pigment gene after pigment production has already been halts for some time
What are the “Ac” and “Ds” elements?
Ac: ALLOWS the Ds element to move
Ds: what DISRUPTS (is inserted into) the pigment gene
What is the phenotype of each of these genotypes in corn?
Cc
Ctc
Ctc–>Ctc/Cc
Cc: Purple kernels
Ctc: Clear kernel
Ctc–>Ctc/Cc: Variegated kernel
How can transposable elements activate genes?
Transposable elements can have elements capable of acting as a promotor for a gene that it not within itself
In relation to causing chromosomal arrangements, pairing by LOOPING and crossing over between two transposable elements oriented in the SAME DIRECTION leads to ______.
Deletion
In relation to causing chromosomal arrangements, pairing by BENDING and crossing over between two transposable elements oriented in the OPPOSITE DIRECTIONS leads to ______.
Inversion