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9. Gene Expression and Regulation
All living things are organized.
For life to exist, millions of reactions and events must be coordinated.
The cell's hereditary blueprints are directed by DNA.
The DNA is made up of repeated parts.
There is a nitrogenous base, a five-carbon sugar, and aphosphate.
The nucleotide is below.
Deoxyribose is the name of the pentagon-shaped sugar.
The sugar is linked to two things.
The sugar can be attached to any of these bases.
This is very important when it comes to the message of the genetic code.
A single strand of DNA can be formed from a long chain of nucleotides.
There is a small section of a strand.
The sugars and thephosphates have bonds between them.
The sugar-phosphate backbone of DNA is a scaffold for the bases.
A double helix is formed by two strands of DNA that wrap around each other.
The structure of DNA was deduced by three scientists.
Let's look at how the strands get together.
The rungs of the ladder have pairs of nitrogenous bases, while the sides have alternating sugar and phosphate groups.
The nitrogenous bases pair up in different ways.
The edinine in one strand always binding to the other strand.
G-C or C-G is always binding to guanine.
Base pairs are known as base matching.
The two strands are not the same.
If you know the sequence of bases in one strand, you will know the sequence of bases in the other strand.
If the base sequence in one strand is A-T-C, the base sequence in the other strand will be T-A-G.
The strands run in different directions.
The fifth carbon in the sugar ring is at the 5' end of the strand, while the third carbon is at the 3' end.
The 3' end has an OH, while the 5' end has a phosphate group.
The 3' end of the strand is always opposite to the 5' end.
The strands are said to be antiparallel.
The strands are connected by hydrogen bonds.
There are two hydrogen bonds that hold adenine and thymine together.
A-T or T-A are formed by forming two hydrogen bonds.
There are three hydrogen bonds formed by cysine and guanine.
The genetic code is the order of the four base pairs.
Like a special alphabet in our cells, these four nucleotides spell out thousands of recipes.
The recipe is called a gene.
There are around 20,000 genes in the human genome.
All of the DNA for a species is called its genome, and the recipes of the genes are spread out among millions of nucleotides.
A chromosomes is a chunk of DNA in a genome.
Humans have 23 different chromosomes and they have two copies of each, so each human cell has 46 linear chromosomes in the nucleus.
Eukaryotes have linear chromosomes, while prokaryotes have one circular one.
The linear chromosomes are more likely to get tangled in eukaryotes.
The histones are bunched together in groups called a nucleosome in order to keep it organized.
Unwound DNA must be read in order to be wound up equally.
The section of DNA and what is happening in the cell at that time affect how tightly it is packaged.
Euchromatin is the loose form of the genetic material in the nucleus that is active and available for transcription.
The genes of the genetic material are inactive when they are fully Condensed into coils.
The recipe for life is contained in the nucleus and can be passed on to future generations.
We'll look at how they accomplish this in this chapter.
We said in the beginning of the chapter that the cell's genes are hereditary.
The cell's blueprints are created by directing the manufacture of genes.
It is necessary to copy the information in DNA for it to be passed on.
The copying of DNA is called DNA replication.
The first step in replicating is to break the hydrogen bonds on the double helix.
This can be accomplished by an enzyme called helicase.
The fork is shaped like a y.
Each strand can be used as a template for another strand.
The origins of replication are where DNA replication begins.
Because the helix twists and rotates, another class of enzymes, called DNA topoisomerases, cuts, and rejoins the helix to prevent tangling.
The addition of nucleotides to a freshly built strand is done by the DNA polymerase.
Only the 3' end of an existing strand can be added by DNA polymerase.
To start off replication, a short strand of RNA nucleotides is added by anidase called RNA primase.
The final strand contains only DNA after the primer is degraded and replaced with DNA.
A two-stranded molecule is created by building a new partner strand for each of them, which is identical to the original.
The leading strand is made continuously during DNA replication.
The nucleotides are added one after the other.
The lagging strand is made discontinuously.
The lagging strand is made from pieces of the same nucleotides as the leading strand.
nucleotides can only be added to the 3' end of the growing chain if they are added in the 5' to 3' direction.
One of the strands is oriented in the opposite direction when the double-helix is unZIPPED.
The strand needs to be built in pieces because it doesn't work in this direction.
The figure below shows that the leading strand is being created toward the opening of the helix and that the helix continually opens ahead of it.
The lagging strand is only able to build until it hits a previously built stretch, because it is built in the opposite direction of the helix.
The helix can build another fragment once it is untangled.
The continuous strand is created by the fragments being linked together.
Two copies of the original DNA molecule are left after hydrogen bonds form between the new base pairs.
We don't end up with two completely new Molecules when DNA is replicated.
Half of the original molecule can be found in each new molecule.
Half of the original molecule is lost in each of the two new ones, so it is said to be semiconservative.
The problem is that a few bases at the end of a DNA molecule can't be replicated.
The chromosomes lose a few base pairs at the end of replication.
Over time, the genome has put bits of unimportant DNA at the end of a molecule.
The ends are called telomeres.
Over time, they get shorter.
There are a lot of genes involved in DNA replication.
The double helix is untangled into two strands.
A strand has nucleotides added to it.
The fragments are brought together by Ligase.
The helix is cut by Topoisomerase.
The synthesis of the primer is done by the use of RNA primase.
Several key experiments have led us to know that the DNA is the inheritable material.
The first turning point was achieved by some people.
They isolated components from a dead strain ofbacteria.
After following up on a previous experiment, they added each of the cellular components to a stain of living non-viruses.
The second bacteria was able to be changed into a deadly strain by the DNA component.
It means that genes must be responsible for passing on certain characteristics.
Hershey-Chase did the next important experiment.
They used a special type of virus.
They labeled the parts of the viruses with radiolabeled sulfur and the parts with radiolabeled phosphorus.
The labeled DNA was 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465 888-282-0465, but they were still able to replicate and make progeny viruses.
They proved that only DNA is required to give information.
It was not required.
The manufacture of molecule that actually do the work in the body is directed by DNA.
The recipe book is not the chef or the meal.
Scientists say that DNA is expressed when a recipe is used.
The first step is to turn the genes into something.
The RNA is sent into the cell and turned into something.
The biggest group of "worker-molecules" are the genes.
Almost everything that occurs in the cell is regulated by these proteins.
The process of making anRNA from DNA is called transcription, while the process of translation is called translation.
The nucleus and the cytoplasm are where transcription and translation take place.
Because prokaryotes don't have a nucleus, transcription and translation can occur at the same time.
A set of ideas is a dogma.
It has been dubbed the Central Dogma of Biology because of the important flow of information between genes.
Let's talk about its structure before we discuss it.
There are three ways in which RNA differs from DNA.
There is a difference between double- and single-strandedRNA.
The five-carbon sugar is ribose.
A different base called uracil is one of the nitrogenous bases.
Adenine's partner is Uracil.
There is a table to compare the two.
The testing board loves to test you on the differences.
There are three main types ofRNA.
A temporary version of a DNA recipe is sent to the ribosome.
Part of the ribosomes are made up of rRNA.
In Chapter 5 of the book, we talked about the ribosomes as the sites of the synthesis of proteins.
The ribosomes are shuttled with tRNA.
At the right time, it is responsible for bringing the appropriate amino acids into place.
The message carried by the mRNA is read by it.
rRNA, tRNA, and RNAi stay asRNA.
There is another class ofRNA called interferingRNAs.
These are small snippets ofRNA that are made in the body.
These interferingRNAs can bind to specificRNAs and mark them for destruction.
This will be discussed later in the chapter.
Let's see how they direct the synthesis of the different types ofRNA.
A bit of DNA code is transcribed.
Similar to the initial steps in DNA replication, the initial steps in transcription are similar.
The obvious difference is that in replication we end up with a complete copy of the cell's DNA, while in transcription we end up with a small section.
The bit of DNA that needs to be expressed will be transcribed.
If you wanted to make a cake, your cookbook wouldn't leave your vault.
The recipe for the cake would be copied only by you.
Since each recipe is a gene, it is necessary for transcription to occur on a gene-by-gene basis.
The exception to this is prokaryotes because they can make several different types of proteins.
The transcript is called a polycistronic transcript.
Eukaryotes tend to have a single gene that is transcribed to one mRNA and translated into another.
Monocistronic transcripts are what we have.
The three phases of transcription are initiation, elongation, and termination.
The first step in transcription is to unwound the strands using the helicase.
The first strand of the DNA is called the promoter.
A promoter can be seen as a docking site or a runway.
In the chapter, we will talk about how promoter are involved in regulating transcription.
We have to copy only one of the two strands of the single strand ofRNA.
The antisense strand, non-coding strand, minus- strand, or template strand is the strand that serves as the template.
The coding strand is the other strand that is not active.
Just as DNA polymerase builds DNA, the same thing can be done with the addition of nucleotides only to the 3' side of the molecule.
The template strand has a 3' end and a 5' end.
It doesn't need a primer to start transcribing the DNA.
The actual coding part of the gene is upstream of the promoter region.
This way the polymerase can be set up before the bases it needs to transcribe, like a staging area.
The start site is the official starting point.
The template strand of DNA is the basis of theRNA that is built when transcription begins.
The only difference is that when DNA has an adenine, the RNA can't add a thymine.
The uracil is added by the enzyme.
After adding on nucleotides and reaching the end of the sequence, it separates from the DNA template and completes the process of transcription.
A transcript is a copy of the sequence of nucleotides based on the DNA strand.
The coding strand is identical to the template strand with the substitution of uracil.
In prokaryotes, the mRNA is complete, but in eukaryotes it must be processed before it can leave the nucleus.
There are both coding regions and noncoding regions in the freshly transcribed hnRNA.
The regions that express the code are called exons.
There are introns in the mRNA.
Before the mRNA leaves the nucleus, the introns must be removed.
This process is accomplished by a complex of genes.
This process produces a shorter version of the transcript.
There are different ways in which a transcript can be manipulated, and different ways in which exons can be included.
A poly(A) tail is added to the 3' end and a 5' GTP cap is added to the 5' end.
The process of translation is turning an animal's transcript into something.
Each piece of meat is made from the same group of acids.
The ribosome will be read in three groups.
A codon is three nucleotides.
The codon is related to a particular acid.
The genetic code is redundant because there are more than one codon.
The ribosome has a messenger RNA attached to it that waits for the appropriate amino acids to come to it.
That's where tRNA comes in.
One end of the tRNA has an acid in it.
The anticodon has three nitrogenous bases that can complementarily pair with the codon.
The normal rules of base pairs are usually set in stone, but tRNA anticodons can be a bit flexible when they bind with a codon.
The third position is said to have wobbles.
Guaine and uracil are things that don't bind normally.
The "go-betweens" are the transferRNAs.
Each tRNA becomes charged and conjugates to the ribosome in the cell's cytoplasm.
The bonds between the two acids are formed by the charging enzymes.
Three phases are involved in translation: initiation, elongation and termination.
When a ribosome is attached to the mRNA, initiation begins.
The process is aided by holding everything in place and the help of the tRNAs.
There are three binding sites in ribosomes, an A site, a P site and an E site.
As the codons are read, the polypeptide will be built.
A-U-G is the code for the amino acid methionine in all organisms.
The special first AUG of an mRNA is the one that will kick off translation.
When the AUG is read on the mRNA, methionine is delivered to the ribosome.
Lectin is the addition of amino acids.
There are many codons, or "triplets," in the mRNA.
Each amino acid is linked to its neighboring by a peptide bond as it is brought to the mRNA.
A polypeptide is formed when many of the same acids link up.
Stop codons end the synthesis of a polypeptide.
There are three codons that serve as a stop codon.
The ribosome runs into one of the stop codons.
There is a specific segment of DNA that is transcribed.
In eukaryotes, the introns are removed from the mRNA.
A 5' cap and a 3' tail are added.
The ribosome is ready to be translated.
The ribosome is where the free-floating amino acids are picked up.
In translation, the anticodon of a tRNA molecule carrying the appropriate base pairs with the codon on the mRNA.
The ribosome holds new codons in place, allowing the formation of bonds between the amino acids.
Until a stop codon is reached, the newly formed polypeptide grows.
The polypeptide is released into the cell.
In prokaryotes, translation and transcription can occur at the same time.
The prokaryotes lack a nucleus and their translation and transcription are happening in the same place.
Gene expression can be regulated at different times.
Pre-transcriptional regulation is the largest point.
The start of transcription requires the unwound and the binding of the genes to the promoter.
There is a group of molecules called transcription factors that can either encourage or prevent this from happening.
This can be accomplished by making it more difficult for the polymerase to bind or move to the start site.
The ability of the transcription machinery to access a gene can be altered by changes to the packaging of DNA.
These types of changes are called epigenetic changes, and they usually occur through a modification to a histone protein that is involved in winding up the DNA.
A tighter wrap around histone makes it more difficult to access and a looser wrap makes it easier to access.
These are examples of famous models of regulation.
You don't need to memorize them, but you should be aware of how things come together to regulate transcription.
The majority of what we know about gene regulation comes from our studies of E coli.
A group of genes can be controlled by a single promoter, and these units of DNA are called operons.
The lac operon is one of the best known operons.
Structural genes are needed in a chemical reaction.
The genes will be transcribed at the same time.
There are threeidases in the lac operon that are involved in digestion.
The promoter gene is where the polymerase begins to work.
The region that controls whether transcription will occur is called the operator.
The repressor is a regulatory gene.
The operator can be attached to the repressor.
The operator will not be transcribed if the repressor is binding to them.
If the repressor doesn't bind to the operator, the RNA polymerase moves along the operator and the transcription occurs.
Lactose binding to the repressor causes it to fall off the operator and turn on transcription.
The lac operon can be seen in two diagrams on the next page.
The mechanism for turning on and off the trp operon is the same as for other operons, but only in the presence of high levels of tryptophan.
There is a pathway that codes for the trp operon.
The operon is turned off when the trp repressor is binding to the operator.
A high level of tryptophan prevents the further synthesis of tryptophan.
There are two diagrams showing the trp operon when and when tryptophan is present.
Post-transcriptional regulation occurs when a cell decides that it doesn't need to translate an RNA into aprotein.
This is where the RNAi comes into play.
TheRNAi molecule can bind to it.
The double-stranded RNA is usually single stranded.
This signals to some special destruction machinery that the double-stranded RNA should be destroyed.
Post-translational regulation can occur if a cell has already made a protein, but doesn't need to use it.
This is a regulation that is used to regulate the speed at which the cell needs enzymes.
It's easier to make them ahead of time and then turn them on or off.
This can involve binding with other proteins.
It is possible that other things will need to be made in order for the protein to function.
It was done by dividing.
The cell can change shape and organization many times.
This process is called evolution.
A diploid cell called a zygote is formed when an egg is fertilized.
The embryo goes through a series of cell divisions after fertilization.
The embryo becomes specialized as these occur.
Any type of cell can be an undifferentiated cell.
The future options of a cell are limited once it begins to specialize.
The cell must change in order to differentiate.
Some genes might be turned off.
Cells called organizers release signals to let them know how to grow.
A cell destined to become a muscle might have an increase in things that make it flexible, while a cell destined to become bone might have a decrease in those things.
The future muscle cell can't become a bone cell once the change has been made.
Cells don't typically go backwards.
Homeotic genes turn certain cells in the early embryo into future-this or future.
The Hox genes are a subset of homeotic genes.
Timing is important for the function of these genes.
The embryo needs to be modified at the right time.
The embryo may be developed with the brain in the wrong place, with too many limbs, or with only one side of the body.
embryos that are damaged will usually stop developing.
The developing embryo uses a tool called programmed cell death.
The cells that used to exist in the spaces between your fingers and toes are no longer needed, and when they are, they undergo apoptosis.
Think of it as an eraser that wipes out the webbing between fingers and toes.
There is an error in the genetic code.
The damage to the DNA can't be repaired or it can't be repaired correctly.
Radiation and chemicals can cause damage.
It can happen when a polymerase makes a mistake.
There are two types of polymerases, DNA andRNA, which have different abilities.
If a mistake is made, it is not usually as bad as if it were a permanent molecule.
Since it is passed on from cell to cell and from parent to child, it is important.
The mistake will become a gamete if it occurs in a germline cell.
Errors in the DNA are not a problem unless the error causes a change in the gene product.
An error in a recipe in a cookbook won't hurt anyone unless the recipe is changed and the error causes a big change in the recipe.
There are different types of effects that can be caused by amutation.
The result will be a change to the individual's genetics.
This can be beneficial, detrimental, or neutral to the individual.
Base substitution is when a single base is replaced with another.
The original codon becomes a stop codon when there is a nonsensemutation.
The original codon is altered due to Missense mutations.
When a codon that codes for the same amino acid is created, it doesn't change the corresponding sequence.
There are two types of genes.
Gene rearrangements involve deletions, duplications, and inversions.
Deletions and inserts result in the loss or gain of a gene.
They can either add or remove as little as a single base or as much as a large sequence of DNA.
The introduction or deletion of bases can cause a change in the sequence of codons used by the ribosome to synthesise a polyprotein.
An extra copy of genes can be caused by Duplications.
One copy of the gene can maintain the original function and the other can evolve a new function, which may result in new traits.
Changes in the orientation of chromosomal regions can result in inversions.
If there is an important regulatory sequence involved, this may cause harmful effects.
When two different chromosomes break and rejoin in a way that causes the DNA sequence to be lost, repeated, or interrupted, translocations occur.
Transposons can cut/paste themselves throughout the genome.
Errors in gene expression can be caused by the presence of a transposon.
When the chromosomes are not separated correctly, there is a nondisjunction.
This can cause whole chromosomes to be duplicated in a gamete, which can cause three copies of a chromosomes in offspring.
Polyploidy can cause increased vigor in plants due to incorrect numbers of chromosomes.
Common pathogens arebacteria andviruses.
Bacteriophages are viruses.
Viruses need a host to replicate and sometimes lyse the host cell.
The human body has a collection ofMicrobes.
We depend on a lot of organisms.
Characterizing and understanding this population is a growing area of research.
Common pathogens come in many shapes and sizes.
Sometimes they cause harm and sometimes they don't.
You may have heard of "gutbacteria" before, but this is a special colony ofbacteria that lives inside each one of us.
It makes some things we need.
There is a mutualistic relationship between us and our gutbacteria.
This does not increase their genetic diversity.
They can swap some of their genes with other cells.
Increased antibiotic resistance is a result of genetic variety.
Chapter 10 shows how an increase in genetic variation makes it more likely that a population will survive a catastrophic event.
Viruses can infecting cells.
They need a host cell's machinery to replicate.
The main components of a virus are a capsid and genetic material.
A host is a type of cells that a Viruses are specific to.
Viruses want to replicate and spread.
Aviruses need to make more genome and capsid in order to do this.
They become new viral particles.
The host can't provide everything the virus needs, but the viral genome has genes for building the capsid.
If the viruses have genomes split between several chromosomes, there will be mixing of the genomes.
A blend of the two viruses is what a new virus particle might be.
A virus that can be studied is a bacteriophage.
The lytic cycle and the lysogenic cycle are two different types of replication.
The host cell's machinery is used to replicate the genetic material by the virus.
These spontaneously assemble into mature viruses and cause the cell to break open, releasing new viruses into the environment.
In the lysogenic cycle, the virus enters the host genome and remains inactive until it is triggered to switch into thelytic cycle.
A virus can hide in a cell for a long time.
The cell may replicate the virus during this time.
By the time the lytic cycle is triggered, the virus may have been replicated many times.
When a virus excises from a host genome, it sometimes takes some of the bacterial cell's DNA with it.
New viral particles with the viral genome are accidentally packaged into the host DNA.
It is possible for a cell to get infections with the viral genome and the stolen piece of bacterial DNA at the same time.
If that chunk held a gene for something like antibiotic resistance, the next cell will gain that trait.
The transfer of DNA between cells is called transduction.
The way in which a Viruses break their way out of the cell is different from the way in which a Viruses break their way out of the cell.
Since animals cells don't have a cell wall, viruses often bud out of the membrane in a process similar to exocytosis.
When a virus does this, it takes with it a chunk of the host cell.
There are Viruses with a Lipid Envelope.
Retroviruses like HIV can be inserted into a host genome with the help of an enzyme called reverse transcriptase.
The high rates of mutation are due to the lack of proofreading mechanisms.
These viruses are difficult to treat because of the high rate of mutation.
They evolve quickly as they are naturally selected.
New drugs are needed to treat the resistance.
If two viruses are in the same cell, they can change quickly.
A chimera of the original two viruses can be created with the recombine and mix of the gene segments of each virus.
Genetic variation can be increased by this.
The Central Dogma can be used to research and cure diseases.
A unique DNA molecule that is not found in nature can be created by combining multiple sources of DNA.
The introduction of a eukaryotic gene of interest into a bacterium for production is a common application of the technology.
It is possible to hijackbacteria and put them to work as small factories.
Genetic engineering is a branch of technology that creates new organisms or products by transferring genes between cells.
It would have taken weeks of tedious experiments to identify and study specific genes a few decades ago.
Billions of identical copies of genes can be made in a few hours thanks to the use of the polymerase chain reaction.
The process of DNA replication is slightly modified.
There are lots of DNA nucleotides mixed together in a small PCR tube.
The tube is heated, cooled, and warmed in a thermocycler.
The hydrogen bonds break when the machine is heated.
As it cools, the primers bind to the sequence we want to copy.
When it is warm, the polymerase adds nucleotides to each strand.
There are two identical double-stranded DNA molecules after the first cycle is over.
Two double-stranded DNA segments will be copied into four when the second cycle is over.
As much as needed is created by the process.
A thermocycler is used in science labs.
It is used to study small amounts of DNA from crime scenes, determine the origin of our foods, detect diseases in animals and humans, and better understand the inner workings of our cells.
It is now possible forbacteria to make Insulin, the hormone that lowers blood sugar levels.
The process of givingbacteria foreign DNA is called transformation.
The plasmid is a small circular DNA molecule.
Sometimes a plasmid is predesigned to have some special helpful genes in it, and together these are called a vector.
There are genes for antibiotic resistance in plismid.
The plismids and the gene of interest are cut with the same restriction enzyme, which creates compatible sticky ends.
The plasmid is inserted with the gene into it.
Thebacteria are transformed into something else.
The heat shock method is used in most AP Biology courses.
The ones that did not take up the plasmid are not needed to be transformed.
This is where the antibiotic resistance genes come in.
Only those with the resistance gene can be grown in the presence of an antibiotic.
This laboratory technique has been used to mass-produce important proteins used for medicine, and it also plays an important role in the study of gene expression.
Transfection is a technique that puts a plasmid into a cell instead of abacteria cell.
This is more difficult than transformation.
Transfection is not as useful for making large quantities of something as it is for eukaryotic cells.
The ability to observe differences in different preparations of DNA is an important part of DNA technology.
DNA fragments can be separated by using gel electrophoresis.
The negatively charged genes migrate through a gel toward the positive pole of the electrical field.
The smaller the fragments, the faster they move.
The restriction enzymes are used to create a molecule.
Each person's DNA is slightly different, so the patterns created after cutting are unique to them.
Some people might have a sequence that is cut many times, resulting in many tiny fragments, and other people might have a sequence that is cut frequently, resulting in a few large fragments.
When restriction fragments of the same species are compared, they differ in length because of differences in DNA sequence.
RFLPs are fragments that are called restriction fragment length polymorphisms.
RFLPs from the DNA left at a crime scene are compared to RFLPs from the suspect's DNA.
Modern scientists use the process of DNA Sequencing.
Scientists can determine the order of the nucleotides in a molecule.
By knowing this, scientists could design their own plasmid and use it to study a gene.
The cell's genetic material is called DNA.
The two antiparallel strands are connected by bonds of nitrogenous bases and are pointed toward the middle.
The strands are oriented antiparallel with 3' and 5' ends and twist into a double helix.
The genome is all the DNA in a cell.
It is divided into chromosomes and genes that are related to each other.
The first step in DNA replication is to separate the strands at the origin of the replication fork.
A single strand of the antisense/non-coding/template strand is read by the polymerase and added to a single strand of the coding/sense strand.
The A-site, the P-site, and the E-site are where the ribosome is located.
The anticodon is similar to a codon.
The base-pairing is sometimes not normal.
When a tRNA binding, it brings the corresponding amino acid to the growing polypeptide.
Gene expression is regulated by various reactions and regulators after translation.
Depending on the needs of the cell, this regulation can either increase or decrease the expression of genes.
There can be changes in the DNA message.
There are either small or large deletions, additions, and swaps.
There are some examples of biotechnology, such as the recombinant DNApolymerase chain reaction.
Bacteriophages are viruses.
Viruses need a host to replicate and sometimes lyse the host cell.
Chapter 15 contains answers and explanations.
A geneticist has discovered a yeast cell that can add nucleotides in both the 5' to 3' and 3' to 5' directions.
A eukaryotic gene, which does not normally undergo splicing, was exposed to a known carcinogen.
The length of the gene'sprotein was shorter after exposure.
There are several steps in the process of DNA replication.
A researcher inserts a human lysosomal membrane protein into a bacterium to produce large quantities of the molecule for later study.
Short palindromic sequence in DNA is recognized by a restriction enzyme called Bam HI.
The DNA is cleaved by the enzyme when it recognizes it.
The term transformation was created by a researcher who noticed that nonpathogenicbacteria with heat-killedbacteria producedbacteria that became deadly in mice.
The effect each of the genes has on the process is being determined by a Biologist.
She sees a lot of short and long DNA fragments in one experiment.
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