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59 Cards in this Set
- Front
- Back
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In the time of 1910-1940 what did scientists believe genes were made of ? |
Protein instead of DNA, since proteins were precieved to be more complex and more likely to store genetic info |
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In 1952 what did Alfred Hershey and Martha Chase show ? |
They showed that DNA is the genetic material of some viruses |
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What is a bacteriophage ? |
A virus that infects bacteria -During infection virus attaches to bacterial cell surface and injects material into the cell |
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What is the most studied bacteriophage ? |
Phage T2 which infects E.coli is one of the best studied |
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What is purpose of hershey and chase experiment? |
They wanted to figure out if the main function of genetic material -In order to distinguish b/w protein and DNA they realized the protein in T2 virus contain sulfer but not phosphorus. -Where the DNA contains phosphorus but not sulfur -By using these ideas they were able tot race the fates of both proteins and DNA during infection process |
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Process of the hershey chase experiment? |
Process: Mixed phage with bac cell allowing particles to attach to surface **After infection of bac. empty phage protein coats(ghosts) were removed in a blender **Cells recovered by centrifugation** |
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Results of the hershey chase experiment? |
Since the 32P remained with the bacterial cell, this indicates that the cell genetic material is in DNA since DNA contains a phosphate group.
Where the 35S was released into the surrounding medium since that is the molecule that is associated with protein |
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How and what did chargraff seperate A&G and C&T into ? |
He used chromotographic methods to seperate ATCG, While discovering A&G are purines and C&T are pyridamines |
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What are Chargaff's Rules ? |
1)Percentage of bases does not vary with individual, age, tissue or nutritional state or environment 2)Number of adenines is equal to number of thymines( Purines=Pyridamines) 3)Purine vs pyridine ration indicates relatedness |
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Who are key individuals in X-Ray diffraction? |
-Watson and crick used evidence that originally came from an X-ray diffraction picture of DNA produced by rosalind franklin **Experiments were carried out by wilkins and franklin** **Finding that DNA is a long thin helical molecule** |
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Who were the scientists figured out the structure of DNA ? |
Watson and Crick figured out that: -the DNA moleucle is a double helix -Antiparallel -Major and minor grooves -Chains are complementary |
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What are components of DNA double helix ? |
**Sugar-phosphate backbone: outside of helix** **Pu-Pyr pairing consistent with Chargaff rules** **Strands are antiparallel, complemntary and function as a template for replication** |
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What are some of the alternative forms of DNA ? |
B-DNA Normal form of DNA - Right handed
Z-DNA Zigzag pattern, longer and thinner then B-DNA. Biological significance unknown
A-DNA Right handed helix - Dehydrated B-DNA Shorter and Thicker - dsRNA |
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What is a supercoiled DNA ? |
A DNA tht is twisted upon itself and can go between a supercoiled state and a nonsupercoiled state(relaxed) |
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What are the types of supercoiling? |
Positive supercoiling -involves tighter winding of double helix reducing opportunities for interaction
negative supercoiling -Associated with unwinding of double helix giving its strand an increased access to proteins involved in DNA replication or transcription |
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What does supercoiling affect? |
-Spatial organization of DNA -Energy state of DNA |
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What does the enzyme topoisomerase do ? |
-Interconversion between relaxed and supercoiled forms of DNA **can induce and relax supercoiling** |
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Two types of topoisomerase functions ? |
Type I topoisomerase supercoiles areare removed by cleaving one strand of DNA passing unbroken strand through break
Type II topoisomerase are removed by cleaving both strands of DNA and passing unbroken region of DNA |
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How can DNA be denatured? |
Raising temperature or pH |
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How can DNA be renatured ? |
Denatured DNA can be renatured by lowering the temp to permit H-Bonds b/w strands to be reestablished |
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What would be used in southern blot analysis |
DNA-DNA , RNA-DNA |
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What would be used in northern blot analysis |
RNA-RNA(Northern blot) |
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What is the DNA melting temperature (Tm)? |
The temperature at which one half of the absorbance change has been achieved |
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What does GC content of DNA do to Tm ? |
Melting temperature of DNA increases with its GC content, due to a higher number of H bonds **3 H-Bonds in G-C **2 H-Bonds in A-T |
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What is the genome ? |
The genome of an organism consists of all DNA that contains one complete copy of all genetic info of that organism or virus |
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Genome of a virus and prokaryote ? |
Single or small # of linear/circular DNA/RNA molecules
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Genome of a eukaryote |
Nuclear genome: multiple DNA molecules (chromosomes) Mitochondria & chloroplast genome: circular DNA molecule |
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What are restriction endonucleases ? |
Are proteins isolated from bacteria that cut foreign DNA molecules at specific internal sites -Cutting action of a restriction enzyme generates restriction fragments
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Function of restriction enzyme |
Cleave double stranded DNA only in places where it notices a recognition site
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Process of restriction endonucleases and genetic enginering |
1) "insert" + vector cut with same Restriction enzyme 2) Generation of matching stick ends 3) DNA ligase used to bind sugar phosphate backbones tg
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Larger DNA fragments digested by restriction enzymes are separated in more porous gels called ? |
Agarose** |
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What is a common staining technique of PCR ? |
Soaking the gel in ethidium bromide which binds to the DNA and flouresces orange when exposed to ultraviolet light |
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The sanger method is a type of DNA sequencing that ? |
Is called the chain termination method |
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What is the human genome project ? |
-Project of scientists ran by celera genomics -Costed 3 billion dollars 10 yrs ago -Today 1 month 100,000 -published in 2003 |
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What is observed when comparing calf DNA vs bacteria DNA ? |
Calf DNA contains repeated DNA sequences that are present in multiple copies These multiple copies increase the concentration of such sequences generating more collisons and a faster rate of reassociation then expected in a single copy |
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What are tandemly repeated DNA? |
A category of repeated DNA since copies are arranged next to eachother in a row.
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Minisatellite refer to ? |
Short regions of DNA 100-10,000 bp in total with tandem repeats of 10-100 bp |
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Microsatellite refer to ? |
The repeat unit is only 1-10bp and only 10-100bp in length. |
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What are short tandem repeats ? |
Many DNA fingerprinting applications analyze the length of these short repeated sequences -STR sites chosen for DNA fingerprinting vary in length from person to person since diff in number of times basic repeat unit is repeat |
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Interspersed repeated DNA are? |
Main type of repeated DNA scattered around the genome -Most interspersed repeats consist of transposable elements(jumping genes)
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Why are transposable elements called "jumping genes" |
cause they move around the genome and leave copies of themselves wherever they stop |
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What are LINEs? |
long interspersed nuclear elements which measure 6000-8000 bp in length accounting for roughly 20% of genome **contain gene required for their own mobilization** |
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What are SINEs? |
Consist of short repeated sequences less then 500 bp in length that do not contain genes, instead on enzymes made by other elements for their movement **rely on enzymes from elements to move them(10% human genome) |
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What is RFLP(restriction fragment length polymorphism)? |
differences between individual DNA fragments produced by restriction enzymes |
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Key step in DNA fingerprinting is? |
Southern blotting |
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Explain the process of DNA fingerprinting (5 step) |
1) Restriction fragment preparation -DNA extracted -restriction enzymes added to produce restriction fragments
2) Gel electrophoresis -mixture of restriction fragments from each sample are separated by electrophoresis
3) Blotting -After DNA on the gel is denatured by raising pH -Single strands transferred onto special paper by blotting
4)Radioactive probe -A solution of radioactive probe added to paper blot Probe attaches only to badns containing complementary DNA
5) autoradiography -R
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How are bacterial chromosomes packaged? |
-Most common arrangment is a single circular DNA molecule in the nucleoid -Negatively supercoiled and folded into loop domains
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How are Bacterial plasmids packaged? |
Plasmids are relatively smalll, circular molecules of DNA that carry genes for their own replication and ofter for one or more cellular functions **Contain own ori** **Carry genes for cellular function** |
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What are chromatin fibers ? |
When bound to proteins DNA is converted into chromatin fibres dispersed throughout the nucleus **When these chromatin fibres condense and fold into larger compact structures they become recognizable as chromosomes** |
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Protiens with most imporant role in chromatin structure ? |
Histones are a group of relatively small proteins whose high content of amino acid lysine and arginine gives them a strong positive charge
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Nonhistone protiens ? |
These are a diverse group of proteins that chromatin contains which play a variety of enzymatic , structural and regulatory roles. |
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What is the nucleosome ? |
This is the basic structural unit of eukaryotic chromosomes, consistting of an octamer of histones **Basic unit of chromatin structure** **"bead" octamer of H2A, H2B, H3 h4+ DNA** **The "String" linker is composed of DNA + H1**
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What is the difference b/w heterochromatin and euchromatin? |
Heterochromatin are segments of chromatin highly compacted and transcriptionally active
Euchromatin are loosely packed and more diffuse |
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What is special about mitochondria and chloroplasts? |
They have their own chromosomes which are usually circular, and do not contain histones |
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What is the nucleus made up of ? |
Nuclear envelope -Composed of two membranes inner and outer -Seperated by a perinuclear space
Studded With Ribosomes
Nuclear pores
Nuclear pore complex -At the nuclear pore, this complex fuses together a channel that is lined with intricate protein structures
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What are nuclear pores ? |
-specialized channel within nuclear envelope -providing direct continuity b/w cytosol and nucleoplasm |
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What is nuclear pore complex ? |
-At the nuclear pore, this complex fuses together a channel that is lined with intricate protein structures -Two paralell rings in called the central granuel -Central granuel is called the transporter since it contains components involved in moving macromolecules across nuclear envelope
**Central granule = Transport** **Fibres extend from both end** **Transport: Diffusion (small molecules) Active Transport (macromolecules) ** |
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What are NLS ? |
Nuclear localization signals are AA sequences that enable the protein to be recognized and transported by nuclear pore complex **Enzymes and proteins needed in the nucleus must be imported from the cytoplasm** |
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What are NES? |
Target the protein and bind to RNA for export through nuclear pores **RNAs and components of ribosomes must be exported from the nucleus**
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