Chapter 9: Molecular Biology

Parents pass on genetic information to their offspring.

The genetic information is stored in the body.
The riboflavin is used to make it.
The basic structure and appearance of cells are formed by some proteins and others that function as enzymes.
The process begins with the creation of a living, functioning organisms.

The underlying mechanisms for this process are the subject of this chapter.

There is a nitrogen base, a sugar, and aphosphate.

The functions of these molecules will be presented in this chapter.

Every individual's genetic makeup is different, except for asexually reproducing organisms and identical twins.

These differences are caused by variations in the sequence of nucleotides.

The first half of the twentieth century led to the identification of the hereditary material and the double helix shape of a DNA molecule.

One strain of the bacterium that produces a polysaccharide coat and causes pneumonia, and a different strain that does not cause pneumonia, were the subjects of an experiment by Frederick Griffith.

The diseasecausingbacteria were killed with heat and can no longer cause pneumonia in mice.
He injected dead and livebacteria into mice to see if they could cause disease.
The mice that died had polysaccharide coats.
Polysaccharide coats would cause disease in the descendants of thesebacteria.

The samebacteria were used to remove the polysaccharide coats from the dead diseasecausingbacteria.

The remaining material was able to transform harmlessbacteria into dangerous ones that can cause disease.
The substance with the same properties as DNA was confirmed by further tests.

The culture media that was separated from the growing medium were found to be radioactive, indicating that the phage proteins did not enter the bacteria.

They used radioactive phosphorous in the second part of the experiment.

The first part of the experiment showed that the growing media had entered thebacteria, but the second part showed that thebacteria were radioactive.
In a follow-up experiment, the researchers found that new phages were also radioactive.
The genetic information needed to make new viruses was provided by the radioactive DNA from the phages.

An X-ray photograph of DNA was produced by chemist Rosalind Franklin using DNA prepared in the lab of biophysicist Maurice Wilkins.

A black-and-white pattern of spots is created by X-ray diffraction.
The molecule consisted of two strands wrapped around each other.
Franklin proposed that sugar-phosphate material formed the outside of the double helix because of its hydrophilic properties, and that the nitrogenous bases were located on the inside of the molecule.
James and Francis Crick proposed a model of DNA that was similar to a twisted ladder, with the vertical sides of the ladder being sugar-phosphate molecules and the horizontal rungs being pairs of nitrogen bases.

The flow of information from genes to traits was studied later.

A copy of the DNA molecule is assembled during the interphase of the cell cycle.

There are two double-stranded molecules of DNA.

The double-helix in front of it is torn by the force of helicase.

As the helix is uncoiled, DNA polymerase assembles short segments of nucleotides along the template strand in the direction away from the replication fork.

The next segment must be assembled after each complement segment.

Only an existing strand is able to hold the nucleotides.

The leading strand and every fragment on the lagging strand must be primered.

When the primer is put in place, DNA polymerase can attach to it.

After the primer is replaced with a new one, the RNA nucleotides are replaced with a new one.

The growth of leading and lagging DNA complement is shown in Figure 9-2.

The leading strand is shown in the figure, but the primer that started it is not.

The growing fragment on the lagging strand still has its primer attached because it must initiate each new fragment.

This is where the details of DNA replication are summarized.

When DNA polymerase is attached to a primer, a new fragment begins.

The primer is replaced with a new one.

The nitrogen base has a total of three phosphates attached to it.

The chemical energy for the process comes from breaking the bonds.

There is a circular prokaryotic chromosome.

There is one unique origin of replication on a prokaryotic chromosome.

There are multiple origins to accommodate the larger size of the chromosomes.

Each fragment of the lagging strand begins when the replication fork moves toward the primer.

There are two problems that can occur when replication reaches the end of the strand.

When there isn't enough template strand to attach, one occurs.

There is a problem when the last one is removed.
The empty space left by the removal of the primer is left unfilled if there is no next Okazaki fragment.

This allows the lagging strand to continue and prevents the loss of DNA in replicated chromosomes.

As the cell ages, telomerase activity ceases in most cells.

When telomerase activity stops, the chromosomes become shorter and important DNA at the end of the chromosomes is lost, resulting in non-viable daughter cells.
The aging of cells has been linked to the loss of telomerase activity.

It is not perfect.

Errors happen.

Each newly added nucleotide is checked to make sure it is compatible with the template strand.

If it does not, the nucleotide is removed and replaced with the correct one.

The undamaged strand is a template for the repair of the damage.

The genes in the chromosomes regulate development, growth, and metabolism of cells.

Depending on the instructions given to the DNA, a cell can be a pea plant, a human, or something else.
It is possible to establish that a cell is a human cell.
If it becomes a cell in the iris of an eye, the DNA will direct other information, such as the concentration of melanin, which influences the appearance of different colors.
The cell is controlled by DNA because it has codes for polypeptides.
The resulting characteristics of the cell are influenced by the chemical reactions that regulate the polypeptides.

One strand of a DNA molecule is used to create a template for a RNA molecule.

Deletions and additions are added to the RNA molecule after it has been transcribed.
In translation, the RNA is used to make a polypeptide.

There are 64 possible ways that four nucleotides can be arranged in triplet combinations.

Some codons code for the same amino acid because there are only 20.
Each of the possible 64 codon combinations has a specified amino acid.
The codon is composed of three nucleotides and has a code for the amino acid arginine.
There are three stop codons in the genetic code.
They signal an end to translation.
Only 61 of the codons actually code for amino acids.
The beginning of translation is signaled by the codon that codes for methionine.

You don't need to memorize the genetic code for the AP exam.

The base-pairings between the nucleotides of the tRNA molecule result in a three-dimensional molecule.

The base-pairing between the third and third nucleotides of the anticodon is often not required.

There are about 45 different tRNAs base-pairs with 61 codons.

A large and a small ribosome subunit is formed when the rRNA molecule is transcribed in the nucleolus.

The ribosome in the cytoplasm coordinates the activities of the mRNA and tRNA.

The TATA box is a sequence found in a promoter region for mRNA transcriptions.

Only one DNA strand is transcribed, and the new nucleotides are not required.

A point of attachment for the ribosome is provided by capping.

The tail has 200 adenine nucleotides.

It seems to control the movement of the mRNA across the nuclear envelope.

Different mRNAs can be produced if different parts of the transcript are removed.

The ribosomal subunits are transported across the nuclear envelope after they are transcribed.

The tRNAs are attached to each other using energy from the ATP in the cytoplasm.

The ribosome has something attached to it.

The sequence of codons determines the sequence of the polypeptide.

One by one, the anticodon of the tRNA brings an acid to the ribosome.

There is a bond between the newly arrived amino acid and the already present ones.

There is a ribosome.

The process is repeated until a "stop" codon is reached and the completed polypeptide is released.

The details are more complex.

In translation, there are three steps: initiation, elongation and termination.

Several GTP molecules provide energy for translation.

GTP acts like an energy supplier.

The tRNA is in the second position.

The middle of three binding sites are occupied by the large ribosomal subunit.

The ribosome is completely assembled with the help of two genes.

The first binding site is always the anticodon of the appropriately base-pairing with the codon of the mRNA.

The newly arrived tRNA is transferred to the second binding site with the help of the second binding site.

When the ribosome moves over one binding site, the tRNA in the middle moves to the third position and the tRNA in the first position moves to the second position.

The first position binding site is empty because of this.

The tRNA in the third position is free to bind with its specific amino acid and provide another delivery.

Each successive tRNA delivers an acid.

As each new tRNA arrives, the polypeptide chain is shortened by one new amino acid, growing in sequence and length as prescribed by the sequence of codons on the mRNA.

The completed polypeptide, the last tRNA, and the two ribosomal subunits are released.

The ribosomal subunits can attach to the same or another mRNA.

The secondary and tertiary structures of the polypeptide are given after it is completed.

The Golgi body may make final modifications to the protein before it functions as a structural element.

Environmental effects such as radiation, ultraviolet or X-ray, and reactive chemicals can cause changes in the genes.

There are various ways to repair damaged DNA.

The damaged DNA becomes a problem.
Most of the time, a partial or complete loss of cell function can be caused by deleterious genes.
New allelic variation is introduced into the population and the potential for evolutionary change when a sex cell is passed on to the next generation.

There are different kinds of changes.

All subsequent nucleotides are displaced one position.

All codons will change if there is a frame shift in a DNA segment.

A point may or may not have an effect.

When the substitution results in a change of the last three nucleotides in a codon, this occurs most often.

There are examples of codons that code for the same amino acid but differ by their third nucleotide.

The effect can be minor, or it may result in the production of a missing part of the body that is unable to carry out its normal function.

There is a missensemutation that causes the hemoglobinprotein to cause the disease.

There is a nonsense mutation that causes the hemoglobinProtein that causes some forms of thalassemia.

Most deletions result in the loss of important genes.

If the duplication occurs within a gene segment, it is likely to cause a frame shift.

A duplicated gene can provide additional products for processes that are in high demand.
Most species, includingbacteria, have genes that are redundant for the one that codes for rRNA, a product in high demand.
Extra copies of a gene give the chance for subsequent changes to create novel variations without interfering with the normal operation of the original gene.

It is believed that the various globin chains of hemoglobin each evolved from a common gene.

There are multiple variations of the gene on two separate chromosomes in humans.

The genes for these glycoproteins are thought to be the result of multiple duplications and divergence of the trypsinogen gene.

This shows how novel genes can come from duplicated genes originally used for something else.

Depending on where the chromosome breaks occur, there may or may not be a significant effect.

One form of Down syndrome occurs when a piece of chromosome 21 is transferred to another.

Three copies of the translocated segment were given to the offspring who inherit this chromosome 14 along with the two normal copies.

They are segments of the genome that have been copied or deleted.

In corn, transposons are responsible for some strains that lack pigmentation.

Most transposons appear to be sitting within introns, but the human genome has as much as 50% of its DNA derived from transposons.

Viruses can be found in cells.

A typical virus takes over a cell's metabolism, assembles hundreds of new viruses that are copies of itself, and then leaves the cell to attack other cells.
The host cell is usually destroyed.

There are different types of cells that a Viruses will attack.

Some viruses only attack one type of cell within a single host species, while others attack similar cells from a range of closely related species.

The host cell's cell membranes contains phospholipids and proteins.

New viruses emerge from the host cell and destroy the cell in the process.

The process repeats after the new viruses are in other cells.
Depending on the nature of the virus, there are variations of this theme.
Important variations follow.

New viral DNA is created when the DNA is replicated and transcribed.

The translated mRNA is used to make the viral proteins.
New viruses are made of the genes.

The RNA is used as a template to make the messenger RNA.

New viruses are made with the translation of the mRNA and the assembly of the RNA.

The virus is inactive until an external environment causes it to start a destructive lytic cycle.

The lysogenic cycle can begin by incorporating the genes of the host into their own.

Retroviruses are a special kind of transposon because there is little specificity to where the viral DNA is inserted.
The cause of AIDS is the human immunodeficiency virus.

The potential for rapid evolution of viruses is great.

The lack of the repair mechanisms associated with DNA replication is what leads to the higher rates of replication errors.
There are more changes to the viruses than there are changes to the humans.

When the genetic material of several different, but related viruses are present in a cell, the evolution of the viruses is augmented.

There is evidence that two strains of simian immunodeficiency virus (SIV), an HIV-like virus in monkeys, recombined to create HIV.

Host populations do not evolve immune-system defenses as fast as the viruses do, so the high rates of mutation intensify their pathogenicity.

Most of the viruses that cause the common cold are all RNA viruses.
New strains of the viruses evolve quickly and remain infectious throughout the human lifetime.

Both Archaea andbacteria are prokaryotes.

They don't have a nucleus or any of the specialized organelles of eukaryotes.
The primary genetic material of prokaryotes is a single, circular DNA molecule.
The chromosomes are duplicated and the cell divides into two cells, each carrying one of the chromosomes.
In prokaryotes, there is no nucleus to divide, so the spindle apparatus, microtubules, and centrioles are missing.

genes that are beneficial but not essential to the survival of the prokaryote are carried by plismids.

The plismids replicate on their own.

The same genes are being replicated in prokaryotic and eukaryotic organisms.

Because prokaryotic chromosomes are circular, replication begins at a single unique origin, progressing in both directions until they meet at the terminated site.
Eukaryotes have multiple points of origin.
The prokaryotes don't have the problems of replicating telomeres because they don't have ends.

It is similar to that of eukaryotes.

Prokaryotic genes do not have introns.
A single transcript may contain multiple genes that are part of a metabolic pathway.
The ribosome is attached to one end of the transcript and begins translation while the other end is still being transcribed.

It is best understood bybacteria.

Through the pilus, the donor bacterium sends chromosomal or plasmid DNA to the recipient.

In some cases, large portions of a donor's chromosomes are sent to the recipient.

A recipient bacterium can become a donor cell when it receives the F plasmid.

When a virus is assembled, it is sometimes assembled with some of the bacterium in place of the viral DNA.

The resident DNA can recombine with the bacterial DNA that is delivered when this virus is in another cell.

Similar to conjugate, transduction can transfer resistance to host cells.

This kind of DNA taking can be accomplished by the use of specialized proteins on the cell membranes.

Some genes are always turned on, but most are not.

Cells are constantly modifying their activities to respond to different conditions.

There are mechanisms that turn genes on and off.

There are multiple genes in an operon that work together to direct a single pathway.

Allosteric regulatory proteins become active when they bind to a specific molecule.

There are two kinds of regulatory proteins.

The inactive repressor produced by a regulatory gene does not bind to the operator.

The structural genes necessary to produce the enzymes that synthesise tryptophan are being transcribed.
In this case, rising levels of tryptophan cause some to react with the inactive repressor and make it active.
The operator region of the active repressor prevents the transcription of the structural genes.

An active repressor is produced by a regulatory gene.

When the operator region is occupied by the repressor, the transcription of several structural genes is impossible.

Some of the lactose is combined with the repressor to make it inactive.

The genes that code for the enzymes that break down can be transcribed by the RNA polymerase.

When both sugars are present, it is a preferential source of energy.

CAP is inactive when cAMP levels are down.
CAP is activated and binding to the operator when cAMP levels are up.

The regulatory processes are negative feedback mechanisms because they turn on remedial processes in response to changes in environmental conditions.

The regulation of gene expression in eukaryotic cells is more complicated than in prokaryotes.

Many organisms are multicellular.

Different gene regulation programs are required for different cell types.

The chromosomes of prokaryotes are simpler than those of eukaryotic organisms due to their larger size.

Multiple genes are located on different chromosomes and need to be activated for certain processes.
In these cases, a more sophisticated system of regulation is required than is present in prokaryotes.

While transcription is still in progress, translation begins.

The nucleus isolated from translation is where the transcription takes place.
There is a greater range of mechanisms that can be used to control the expression of genes.

In line with the complexity of eukaryotic cells, the mechanisms that regulate transcription are similarly complex.

It is more difficult for transcription factors to access the DNA.

Long-term inactivation of genes is associated with DNA methylation.

When an acetyl group is attached, histone molecule loosens their grip on the DNA molecule.

When a group of histones are attached, they are methylated.

A few days after fertilization, one of the two X sex chromosomes in each cell of female embryos is randomly inactivated.

A silenced gene produces a noncoding transcript that is associated with a loss of acetylation in the histone.
The descendants of each cell are the same.
The purpose of X inactivation is to equalize the gene dosage that both males and females express.

The degree to which transcription is activated or repressed is determined by the makeup of the transcription complex.

The promoter region has a box sequence associated with it.

There are two types of transcription factors.

The binding sites are upstream or downstream to the gene.
Each enhancer may be specific to a different timing of transcription or to a specific cell type, and there may be one or more enhancers that are unique to a particular gene.

This allows a single gene to be used to make a specific cell type or stage of development.

They bind to the cytoplasm and block translation.

They bind to, cleave, and degrade the same sequence.

They prevent the transcription of genes.

The two types of molecule that are best understood are single stranded and long stranded.

The origin of the microRNAs is described here.
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Short interferingRNAs originate from double-strandedRNAs that have formed in the cell's cytoplasm or from dsRNAs that have been introduced into the cell.

The truncated dsRNAs are used to make siRNAs.

The tail is degraded as the mRNA ages and degrades.

Sequences rich in adenine and uracil in untranslated regions of the mRNA are recognition sites for other degrading enzymes.

As their shape changes, they lose their function.

Stem cells can become any kind of fetal or adult cell when they divide.

Cells become specialized as development continues, and subsequent cell divisions produce cells that are similar.
Cells become specialized because of the actions of transcription factors.
The process is self-reinforcing once certain genes are turned on or off.
There are genes that are permanently turned off.

Dolly was the first mammal to be cloned.

The nucleus of an unfertilized egg cell is replaced by the nucleus of a fully differentiated adult cell.
This showed that determination can be reversed.

The nucleus from a cell that was fixed was not fixed by implanting it in the stem cell's cytoplasm.

Repetitive DNA can be transferred from one part of a molecule to another, or from one part of a molecule to another.

The transfer of DNA segments can be done naturally.
It's a regular occurrence in the eukaryotes as a result of crossing over during prophase of meiosis.
It is possible to make a copy of the same genetic material with the help of biotechnology.
A range of activities are addressed in this definition.

The antibiotics that are used to combat invading viruses are obtained frombacteria.

The cut across a double-stranded DNA is usually staggered, producing fragments that have one strand of the DNA extending beyond the other strand.

Multiple fragments of foreign DNA are produced by the restriction enzyme.

The genes will be copied from some of the fragments.

A cloning vehicle is a vehicle used to transfer genes.

plamids can be introduced intobacteria by transformation.
The sticky ends are the same as those produced in the foreign DNA.
The antibiotic ampicillin is resistant to this gene.

A bright green fluorescence is presented by this gene.

This is a gene that breaks down Lactose.

There is a restriction site within the lacZ gene.

Cut foreign DNA with cut plasmids.

The foreign fragments that contain the genes to be copied will be fused with the plasmid fragments.

The attachment should be stable by applying DNA ligase.

Some of the plasmids contain foreign genes.

The foreign gene will not be found in other plasmids.

To allow transformation, mix plasmids withbacteria.

The plasmids will be absorbed by some of thebacteria.
Somebacteria will accept plasmids.
Nonrecombinant plasmids will be absorbed by others.

The gene is malfunctioning because of the Z gene.

The Z genes turn X-Gal blue.

Foreign genes are often prevented from being transcribed by introns.

The required genes are obtained directly from the mRNA that codes for them.
The reverse transcriptase is obtained from retroviruses.

It is heated.

The hydrogen bonding holding the double-stranded DNA together is separated by heating denatures.

A single-stranded DNA primer is added after the DNA is cooled.

The polymerase is added.
A special heat- tolerant DNA polymerase is added.
The primer at each end of a single strand of DNA has a DNA polymerase attached to it.
The first dsDNA molecule becomes two dsDNA molecule at the end of this step.

The above steps are repeated.

Each repetition of the sequence increases the number of molecule by molecule.
Billions of copies of DNA can be amplified in hours.

Under the influence of an electric field, DNA fragments of different lengths are separated from one another.

It moves toward the positive electrode since it is negatively charged.

Shorter fragments move further through the gel.
In order to determine evolutionary relationships, gel electrophoresis is often used.

When restriction fragments of the same species are compared, they differ in length because of differences in DNA sequence.

RFLPs from the crime scene are compared to RFLPs from the suspects.
The number of repeats varies greatly among individuals, with two to five base pairs being the most common.

New capabilities have been introduced to human civilization.

There are clear benefits to improvements in the identification and treatment of disease.
Some benefits can be abused while others are debated.
Social and ethical questions can arise.

It is possible to quickly and inexpensive produce many pharmaceuticals.

Human growth hormone, which was previously obtained from human corpses, is now readily available as a product of DNA cloning.
Diabetes and certain forms of dwarfism can be treated with hormones.
Some athletes and celebrities use human growth hormone to increase athletic performance and reduce the effects of aging.

Some diseases can be identified by looking at the genes of the individual.

Symptoms, including early death, can be circumvented.
There are no available treatments other times.
It is not clear whether affected individuals should know that they will suffer from a disease in the future, whether medical insurance has a right to know that they are high-risk patients, and whether society should control the reproductive potential of the individual.
There are issues of individual self-determination, medical privacy, and reproductive rights.

Genes have been inserted into agricultural plants to provide resistance to pests and other environmental conditions.

Genetic engineering can change fruit color, increase crop yields, or extend shelf life.
Several genetically modified crops, including corn, carry the Bt gene that gives plants insecticidal properties.
The chemical produced by Bt is only toxic to certain insects.
This reduces the need for pesticides, which are often used toindiscriminately kill insects.
Other insects that aren't killed by the Bt toxin increase in numbers and need to be sprayed again.
insects that were susceptible to Bt toxin evolve resistance to the toxin In some genetically engineered crops there are uncertain consequences if the transgenic gene is spread to wild plant populations.

Genes have been inserted into domestic animals to produce desirable products or to produce animals that are more vigorous or convenient to rear.

Salmon have been modified with a growth hormone to make them grow faster.
Gene flow into wild populations is a major concern for the salmon.
Milk that contains spider fibers can be used as sutures or industrial products.
Surprisingly, there are often unexpected results with genetically modified organisms.
A GM breed of featherless chickens, developed to simplify marketing preparation, was more prone to insect bites and more sensitive to UV radiation.
Success was impaired because of the feather displays.

Genetically modified organisms in the food chain are controversial.

One of the biggest concerns is the health of the GM plant or animal because of accidentally inserted genes.

The process of breeding two animals with the same trait takes a long time.

Before another round of breeding can occur, the new generation must reach reproductive age.
Within a single generation, reproductive cloning promises to produce copies of any desirable individual.
A cow that produces the most milk, a prize-winning racehorse, or your favorite pet could be used to create many identical copies of exceptional individuals.

reproductive cloning has had mediocre success so far.

Organ failure, a high susceptibility to disease, and shorter than normal life spans are some of the problems.

A review of the material presented in this chapter is provided by the questions that follow.

They can be used to evaluate how well you understand the concepts.
AP multiple-choice questions are often more general, covering a broad range of concepts.
The two practice exams in this book are for these types of questions.

Four possible answers or sentence completions are followed by each of the following questions or statements.

The one best answer or sentence is what you choose.

During translation, the base-pairs of the cytosine, guanine, and adenine nucleotides are attached to the mRNA.

The nucleus and the cytoplasm are where the genes are made.

Questions 9-15 refer to the following diagram.

The names of thenucleotides are referred to in the letters A, G, and C.

The key is used for questions 9-14.

The answer in the key can be used more than once.

The questions that follow are typical of an entire AP exam question or just that part of a question that is related to this chapter.

There are two types of questions on the AP exam.

It takes about 20 minutes to answer a long free-response question.
Sometimes they offer you a choice of questions to answer.
6 minutes is the time it takes to answer a short free-response question.
diagrams can be used to supplement your answers, but a diagram alone is not adequate.

Gene regulation in prokaryotes is simpler than in eukaryotic cells.

In some cases, a single nucleotide change doesn't lead to the creation of something else.

Explain how this can happen in two or three sentences.

Both traditional fingerprints and DNA fingerprints can be used to identify suspected criminals.

There are weak hydrogen bonds between the strands.

It is not a base in any of the genes.

The uracil base is the base that pairs with the adenine DNA nucleotide.

A ribosome is a complex of rRNA molecules.

The uracil nucleotide has a ribose sugar, adenine nucleotides and uracil nucleotides in it, so the remaining choices are incorrect.

The replication of DNA is not involved in the transcription of DNA.

One of the answer choices is not the majoridase for DNA replication.
Before DNA polymerase can attach and begin attaching DNA nucleotides, it is necessary to have the right primer in place.

The adenine nitrogen base, sugar ribose, and three phosphate groups are equivalent to the adenine ribose with two extra groups.

An adenine DNA nucleotide with two extra phosphates is written as dATP.

The process of translation is the matching of ribosomal particles with one another.

There is a sequence of genes.

The sequence of triplets is the same as the sequence of the entire polypeptide.

The triplet-codon reading frame is affected by a deletion of a nucleotide in the mRNA.

If the first nucleotide of a codon is deleted, the second, third, and fourth will become its first, second, and third, respectively.
This is repeated in every other codon.
The final sequence of the polypeptide is likely to be affected by such an arrangement.
Answer choice B will result in a missing acid, and answer choice C will change one acid to another.
The changes may affect the effectiveness of the polypeptide, but not as much as changing many amino acids.
A change in the third position of a codon will often code for the same amino acid, so answer choice D may not have any effect.
The cause of the inherited disorder is the replacement of one of the two chains of the hemoglobin protein with another, which reduces the effectiveness of the hemoglobin in carrying oxygen.
It would be useless if a frameshift in the coding of the genes for hemoglobin happened.

A uracil nucleotide base pairs with an adenine nucleotide when the anticodon and codon nucleotides of the mRNA are present.

The base-pair is the same as in Question 13.

The process of translation is illustrated here.

The anticodon of a tRNA is shown with the codon of the mRNA.

The DNA of all cells is the same.

On the other hand, the genes produced by the two unrelated species are likely to be different, as well as the number of DNA molecule, the length of the chromosomes, and the DNA sequence.

The process of copying is called replication.

transcription and translation are involved.
The translation begins with initiation, continues with elongation, and ends with termination.

The genetic instructions are carried to the cell by the messenger RNA.

The rRNA and tRNA work together to make a polypeptide.

A plismid is a small circular DNA molecule that a bacterium has.

A laboratory process that creates multiple copies of DNA is called DNA amplification.

Answer choice A is a description of the processes that can introduce genetic variation into the genomes ofbacteria.

A nucleic acid is surrounded by a protein coat.

Some viruses have an envelope made from lipids or glycoproteins obtained from their hosts, but they don't have the same type of bilayer membranes as cells.

Introns are intervening in the sequence of the mRNA that is cleaved by snRNPs before it is sent to the cytoplasm.

A promoter region, an operator region, and a series of structural genes are part of the Operons.

The three parts of an operon work together to control transcription, which leads to the regulation of gene expression.

Eukaryotic organisms are multicellular.

Gene regulation must be able to regulate the expression of genes specific to the cell type.

Multiple genes on different chromosomes are regulated at the same time when they all contribute to a metabolism.

If there is a substitution in the third position of the mRNA codon, no new amino acid is designated.

More than one codon codes for the same amino acid, and the third position is the most variable.

The traditional fingerprints can be used to distinguish twins because the genes that make the ridges on your skin that make fingerprints have been altered.

Environmental factors that differ between identical twins during fetal development can affect genes.
The "raw" genetic material, uninfluenced by genes, can't be distinguished from identical twins.

Instructions for producing a specific polypeptide are contained in segments of the DNA.

Chemical end products that appear as traits are produced by many polypeptides that regulate cellular reactions.
The process by which information is transferred from one cell to another is called cell division.
The first step in the process is called transcription.

The DNA fragment that represents the gene is represented by the base-pair of the RNA nucleotides.

If a fragment of DNA contained adenine, cytosine, guanine, and thymine, the RNA nucleotides that would base-pair with it are uracil, guanine, and adenine.
The products of transcription are three different types ofRNA.

The code for the polypeptide is contained in the mRNA.

The mRNA moves to the nucleus.

The translation takes place in the nucleus of the cell.

It requires all three types ofRNA.

The ribosomes attach to the mRNA.

The ribosome has a tRNA attached to it.

There are different kinds of tRNA.
Each kind is specific for a specific part of the tRNA.
The anticodon is a region of three nucleotides.

During the translation process, ribosomes pair the anticodons of tRNAs with the appropriate triplet regions of the mRNA.

The codon specifies a particular acid.
Each of the 64 different mRNA codons has a genetic code.
The stop code is signaled by some codons.
There is a codon that indicates methionine.

The ribosome provides binding sites during translation.

The codon sequence on the mRNA dictates the appropriate amino acid for each tRNA.
The polypeptide chain that is attached to the previous tRNA is transferred to the new one.
The process repeats until the stop codon is encountered, as the ribosome moves over one binding site.

The ribosome separates and the polypeptide is released.

The secondary and tertiary structures of the polypeptide can be created by interacting with one another.

Secondary structure results from hydrogen bonding and can be a helix or a sheet.
There are disulfide bonds between cysteine and R groups of the amino acids.
The final form of the polypeptide may be anidase that can regulate a reaction that will produce a trait.

When you have time, you should discuss every step of the process.

Points are given for each step in the process.
Excess detail in one step does not improve your score because there is a maximum number of points given for each step.
Providing a few pieces of information helps you maximize your score.
The regulation of transcription would provide more information than the question asks.
If you don't include anexplanation of the genetic code, you will probably lose a few points.

Viruses destroy cells.

A viruses has a nucleusc acid core and aProtein coat.
In the lytic cycle of reproduction, a DNA virus enters a cell and uses the metabolic machinery and raw materials of the cell to make more viral DNA and viral protein coats.
Hundreds of new viruses burst from the cell, killing the cell in the process.
In the lysogenic cycle, the virus may temporarily remain inactive as part of the host's genome, to become active only when exposed to radiation.
The lytic cycle begins when the viral DNA is activated.

There are some viruses.

In a lytic or lysogenic cycle, some of these RNA viruses produce the reverse transcriptase to first manufacture DNA.

Viruses do not usually cause disease by the destruction of host cells.

Mostbacteria cause disease by producing toxins, usually waste products of their normal metabolism.

The toxins affect the metabolism of the host.

The host cells and somebacteria compete for the same resources.

The host's response to invasion by foreign bodies is what causes the symptoms of a disease.
In pneumonia, the mucus that accumulates in the lungs is produced by the lung cells in response to the presence of the bacteria.

If time allows, describe other mechanisms such as histone modification.