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Chapter 99 -- Part 2: From DNA to Protein
Gene expression can be regulated by the span of time after transcription.
Within minutes of their synthesis,bacteria are degraded.
The rapid degradation of mRNA may be the reason thatbacteria are able to adapt to changes in the environment.
Human mRNA can translate for hours or weeks.
Red blood cells can be translated multiple times with the help of stable Molecules of mRNA in developing red blood cells.
Recent data shows that as much as 90% of non-protein-coding DNA is transcribed into various kinds of noncodingRNA.
These ncRNAs help bind to and assist the Argonaute proteins.
Scientists are still learning about these regions, but they regulate a lot of our genes.
New information is published almost weekly and three types of ncRNA have been extensively studied.
MicroRNA is a small, single-strandedRNA that is about 22 nucleotides long.
It doesn't code for anything.
Instead, it targets specific mRNA molecules, which can either be degraded or blocked.
At least one-half of all human genes may be regulated by miRNA.
SiRNA is similar to miRNA in size and function.
The blocking of gene expression by siRNA is calledRNAi.
The discovery of how interferingRNA can play a role in the suppression of genes was the subject of the 2006 Nobel Prize in Physiology or Medicine.
This can be accomplished by binding to and destroying mRNA.
The piRNA is a large class of ncRNAs that guide PIWI proteins to complementaries which are derived from transposable elements.
Germ line cells are protected from attacks by transposons.
Following translation, there is a final opportunity to control gene expression.
After emerging from a ribosome, a newly madeProtein may spontaneously fold into its correct shape and begin "working" immediately.
Some newly made proteins have to be activated before they can function.
In an inactive form, a ribosome can be released from and only become an active hormone after being cleaved.
Taking two or more sources of DNA and combining them into one molecule is a form ofombinant DNA.
In nature, this occurs through viral transduction,bacterial transformation, and conjugate and when transposons or "jumping genes" move around the genome.
In the laboratory, scientists can manipulate and engineer genes.
Genetics or genetic engineering is a branch of science that uses recombinant DNA techniques for practical purposes.
Tools and techniques have been developed to manipulate genes.
There is a discussion of the uses for genetic engineering, an explanation of some techniques that are used, and a discussion of ethical issues within the field.
To make a large amount of humaninsulin in large quantities as an inexpensive pharmaceutical.
Gene therapy replaces a malfunctioning gene in a person's cells with a functioning one.
Clinical trials in this area have disappointing results.
The human subjects can become ill from the viral vector.
Sometimes, the gene is inserted successfully and begins to produce the required proteins, but it stops working in a short time.
Many lives will be improved if scientists can master this technique.
To prepare multiple copies of a gene.
The ability to make multiple copies of a single genes is a great research tool.
To clean up the environment.
One modified species can eat toxic waste.
The plasmid will be inserted into a cell that will carry it.
To take up a plasmid, a bacterium must be made competent.
The selected gene and the plasmid are being cloned as thebacteria reproduce themselves.
There are millions of copies of the gene.
Pick the bacteria that contain the selected gene and harvest them from the culture.
The late 1960s saw the discovery of restriction enzymes.
They are taken frombacteria which use them to fight off attacks.
There are specific recognition sites that are cut by restriction enzymes.
When these cuts are staggered, single-stranded sticky ends form a temporary union with other sticky ends.
The fragments that result from the cuts are called restriction fragments.
Explain how technologies can be used to manipulate heritable information.
Scientists have isolated hundreds of different restriction enzymes.
They were named after thebacteria in which they were found.
Eco RI is one of the examples.
Gene cloning is one of the uses of restriction enzymes.
The rate of movement of the large molecule of DNA is determined by the electric field created by the agarose gel.
The faster the molecule runs, the smaller it is.
Due to the presence ofphosphate groups in PO 4 3-, the DNA flows from the cathode to the anode.
The concentration of the gel can be changed to make it harder to separate smaller pieces.
It's also used to separate the two acids.
If the DNA is going to be run through a gel, it must be cut up by restriction enzymes into pieces small enough to migrate through the gel.
There are many ways in which the DNA can be analyzed.
The sequence of bases A, C, T, and G can be determined with the help of the gel.
The location of a specific sequence within the DNA can be identified with a DNA probe.
Three larger pieces and one short piece are in Lane 1.
There is a piece of uncut DNA in Lane 3.
The farther away the piece of DNA has traveled from the well.
A DNA probe is a single strand of nucleic acid molecule that is labeled with radioactivity.
The probe bonds to the sequence and radioactivity allows scientists to locate it.
A person with an inherited genetic defect can be identified by using the DNA probe.
A piece of DNA can be copied or amplified using a cell-free, automated technique called polymerase chain reaction.
Billions of copies of a fragment of DNA can be produced in a few hours.
In order to amplify the piece of DNA, it must be placed into a test tube with Taq polymerase, along with a supply of nucleotides and a primer.
These copies can be used in a comparison with other DNA samples.
In order to make the necessary primer, some information about the target DNA must be known in advance.
The piece that can be amplified must be small.
Contamination is a big problem.
Obtaining accurate results could be difficult or impossible if a few skin cells from the technician accidentally get into the sample.
A crime scene sample can have dire consequences if an error is made.
A restriction fragment is a segment of DNA.
The restriction fragment pattern is different in every individual and scientists discovered that when they compared noncoding regions of human DNA across a population.
A human's fingerprints look like a barcode after a RFLP analysis of their DNA.
RFLPs are unique to each person, except in identical twins.
They can be used in paternity suits to determine if a man is the father of a child because they are inherited in this way.
RFLPs are used to identify the perpetrators in rape and murder cases.
The suspect's DNA is compared against the victim's.
The cases can be solved with a high degree of certainty because of the accuracy of RFLP analysis.
In several instances, prisoners who have been imprisoned for a long time for violent crimes have been proven innocent by the use of DNA evidence.
The introns present a problem when scientists attempt to clone a human gene.
There is no way to edit introns after they are transcribed.
Scientists must insert a gene with no introns in order to clone a human gene.
Scientists extract fully processed mRNA from cells and then use the reverse transcriptase obtained from retroviruses to make DNA transcripts.
The complete coding sequence of interest but without introns is carried by the resulting DNA molecule.
The DNA produced by retroviruses is called cDNA.
The acronym stands for Clustered Regularly Interspersed Short Palindromic Repeats.
It is a tool that allows scientists to modify an organisms' genes.
There is a stretch of DNA that can be altered with the help of the Cas9 enzyme.
The whole unit is referred to as CRISPR-Cas9.
The naturally occurring genome editing system inbacteria was adapted for protection against viruses.
The genomes of invading viruses are captured by the bacteria and they use them to create segments of their own.
TheArrays allow thebacteria to remember the viruses.
If the viruses attack again, thebacteria produceRNA segments from the CRISPR array to target the viruses' genes.
The virus is disabled by the bacterium by cutting the DNA apart.
They were the first to propose that CRISPR-Cas9 could be used for gene editing.
Their work has been further developed by many research groups for the treatment of diseases.
In November of last year, the journal Science reported the first time that a person's genome was altered with the help of CRISPR.
Many people are worried about the consequences of genetic engineering.
Some of the concerns are discussed in this section.
The majority of the milk in stores comes from cows that have been given a genetically engineered bovine growth hormone to increase the amount of milk they produce.
Many people are worried that this hormone will cause problems for people who drink milk.
The vegetables people eat have been genetically engineered.
People are concerned that the genes that have been inserted into the vegetables may be harmful to those who eat them.
Personal information about someone's genetic makeup can be held on tiny DNA chips.
A person can be scanned with the chips for over 7,000 genes, including the immune system and breast cancer genes.
Many people would like to know if they carry these genes, but the possibility that the personal information on a DNA chip might not remain private has caused a lot of controversy.
If your health insurance company learns that you carry a harmful gene, it might not cover you or charge you a higher premium.
If a company learns that you might be disabled with a serious illness in the future because of a defect in your personal genetic makeup, it might refuse to hire you.
The discussion in Big Idea: IST was advanced by this chapter.
It shows how genetic information gets from one generation to the next.
The historic search for heritable material, DNA structure, replication, transcription, translation, and regulation of genes are included.
Many scientists carried out a number of experiments that proved that the heritable material is DNA.
You have to understand and be able to analyze the work of Meselson and Stahl.
The double helix of the DNA molecule is a repeating unit of the nucleotides.
There is a sugar, aphosphate, and a nitrogen base in each of the nucleotides.
The X- or Y-shaped structure we recognize as a chromosomes is what the histones are packaged with inside a nucleus.
There is a semiconservative pattern in the genes.
A strand is a template for the formation of a new strand composed ofcomplementary nucleotides: A with T and C with G. The process of mismatch repair is carried out by the DNA polymerase.
The template for protein synthesis is the sequence of nucleotides in DNA.
Genetic information is transmitted with a high degree of fidelity through the processes of transcription in the nucleus and translation at ribosomes.
There are errors, called mutations.
Changes in an organism's genotypic makeup can affect its phenotype and make it more or less adapted to its environment.
Understand how to use the genetic code shown on to figure out what polypeptide would form from a particular sequence.
Gene expression can be altered before or after transcription, by altering the structure of the chromatin or by blocking the binding of the polymerase to the promoter.
Understand how you would use the tools and techniques of biotechnology to solve a problem.
You are shown an image of an electrophoresis gel containing bands of DNA from a child and from a man whom the child's mother claims is the child's biological father.
A researcher is studying genetics.
He used two strains of the bacterium.
The pathogen X-strain has an outer capsule that protects it from the mouse's immune system.
In mice, Y-strain does not cause pneumonia.
The researcher injected two different mice with different strains ofbacteria.
The mouse died after being injected with X-strain.
The other mouse was healthy after being injected with Y-strain.
The researcher carried out another experiment based on his initial findings.
There can be a horizontal transfer of genes.
He injected the X-strain into the mouse.
The mouse was healthy this time.
He injected a mouse with a heat-killed X-strain and a Y-strain.
If the researcher's hypothesis is correct,bacteria can transfer genetic material from one bacterium to another.
Predict what happened when the Y-strain was injected into the mouse.
Proper development depends on the number of active copies of a gene.
Predict which of the following would be the most harmful.
Humans have about 22,000 genes, the same as a roundworm, according to the findings from the Human Genome Project.
In 1952, Alfred Hershey and Martha Chase carried out an experiment that proved that genes are heritable.
The T2 bacteriophage is a phage that can cause E. coli in the human gut.
Hershey and Chase were aware that the T2 bacteriophage reprogrammed the E. coli cell to produce thousands of T2 viruses.
It was clear that the T2 bacteriophage had something in it.
Hershey and Chase had to show how this transfer was accomplished.
There are two phage cultures, one growing in radioactive sulfur and the other in radioactive phosphorus.
The following chart shows the protocol.
If guanine makes up 28% of the nucleotides in the sample, then it would make up 10%.
The cell carries the codon sequence.
The new codon sequence reads as follows.
There is a particular triplet code.
There are two X chromosomes for females and two Y chromosomes for males.
The double helix in DNA consists of two antiparallel strands.
There is one strand that runs from 5' to 3'.
In order for a gene to be transcribed, it must be binding to the promoter.
When an active repressor binding to the operator, transcription is blocked.
Allolactose prevents the repressor from binding to the operator.
This allows the promoter to turn on the operon.
Although it is a true statement, Choice D doesn't say anything about transcription.
The substance from the dead X-strainbacteria was transferred to the Y-strain cells.
The "transformation factor" was identified by the work of the three authors.
It is responsible for the random inactivation of one of the X chromosomes in a human female.
If this happened, females would have double the normal X chromosomes genes and the proteins that are produced from it.
Alternative splicing involves the fact that a single gene can be transcribed in many different ways.
bacteria can take genes from otherbacteria The reverse transcriptase is found in retroviruses.
Deletions cause a reading frame shift.
A reading frame shift at the beginning of an exon or coding sequence would be the most serious because it would disrupt the lengthy sequence that follows.
For the same reason, one at the end of an exon would be less serious.
exons and introns are not included in the human genome.
There are structures that remove introns unrelated to the question.
After it has been translated, Choice D is not a correct statement.
The mechanism that controls how much is degradation.
There are three types ofRNA.
The three stages of transcription are initiation, elongation, and termination.
The process occurs in a semiconservative fashion.
According to the base-pairing rules, the codons of the mRNA strand at the ribosome are carried by the tRNA molecule.
Take a look at the sketch of a stretch of DNA.
Each will have a band on the gel.
There is one large piece, one small piece, and one very small piece.
It was the first restriction that was discovered.
It cuts DNA at certain recognition sites.
Choice A is referring to T2 bacteriophage.
Choice B refers to the bacterium E. coli, not the restriction enzyme.
Eco RI is not a correct choice.
It is not possible to add nucleotides to a naked strip of DNA.
There must be a primer there first.
Choice A is referring to something.
Choice B is referring to a single strand.
Choice D is referring to something.
UUU and UUA both code for phenylalanine.
Malaria is endemic in West Africa and Southeast Asia.
People with the trait are resistant to Malaria.
It is not common in the Middle East.
Caucasians are less likely to suffer from the disease than do people of other races.
There are similarities between codons and anticodons.
It was the radioactive 32 P part of DNA that entered the E. coli.
That fact proved that the material is heritable.
The radioactive 35 S did not enter the E. coli.
It is important to remember that the RNA contains uracil.
The AGA strand is 3'-ACU UCU GGC-5' if the DNA segment is 5'.
Introns are removed with the help of snRNPs and a 5' cap and poly(A) tail are added.
There are three replacements for the word "thymine" in RNA.
The pyrimidine is the purine.
It leaves 44% for adenine and thymine.
The percentage of thymine in the DNA is 22%.
Read the chart to find out the amino acid for that codon.
None of the other choices fit the pattern.
The AGU codes for the serine and AGC codes for the AGC.
The GGU codes for the glycine and the GGG versions.
Multiple codons produce the same amino acid, so there is no change in the sequence.
No polypeptide will be produced when the cell stops reading the strand.
If the triplet in DNA isAAA, the codon on the mRNA and the anticodon on the tRNA is UUU.
The majority of the remaining DNA is involved with gene regulation.
They can turn normal proteins into misfolded ones.
The promoter can be binded to with the help of the repressor.
transcription occurs when the promoter is binding to the RNA polymerase.
The lac operon does not allow for transcription when the repressor is binding to the operator.
Small pieces of DNA are amplified by a cell-free system.
Restriction is found inbacteria.
Eco RI was the first restriction enzyme to be discovered.
Every person has a set of RFLPs.
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