Chapter 9: MICROBIAL GENETICS: Book

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Figure 9.7 Completion of chromosome replication in bacteria: (must View Photo to understand) (a) As replication proceeds, one double strand loops down. (b) Final separation is achieved through action of topoisomerase IV and the final release of two completed molecules. The daughter cells receive these during binary fission.

(a) As replication proceeds, one double strand loops down. (b) Final separation is achieved through action of topoisomerase IV and the final release of two completed molecules. The daughter cells receive these during binary fission.

Figure 9.8 Summary of the flow of genetic information in microbes. DNA is the ultimate storehouse and distributor of genetic information.

(a) DNA must be deciphered into a usable cell language. It does this by TRANSCRIBING its code into RNA helper molecules that TRANSLATE that code into protein. (b) Other sections of the DNA produce very important RNA molecules that regulate genes and their products.

Process, view, and rewrite Figure 9.16 Speeding up the protein assembly line in bacteria. on p249

(a) The mRNA transcript encounters ribosomal parts immediately as it leaves the DNA. (b) The ribosomal factories assemble along the mRNA in a chain, each ribosome reading the message and translating it into protein. Many products will thus be well along the synthetic pathway before transcription has even terminated. (c) Photomicrograph of a polyribosomal complex in action. Note that the protein "tails" vary in length, depending on the stage of translation.

1. RIBONUCLEIC ACID (RNA) is a _____-stranded molecule that exists in helical form. This single strand can assume secondary and tertiary levels of complexity due to bonds within the molecule, leading to specialized forms of RNA (tRNA and rRNA— see figure 9.8a). 2. RNA contains _____, instead of thymine, as the complementary base-pairing mate for adenine. This does not change the inherent DNA code in any way because the uracil still follows the pairing rules.

1. RIBONUCLEIC ACID (RNA) is a single-stranded molecule that exists in helical form. This single strand can assume secondary and tertiary levels of complexity due to bonds within the molecule, leading to specialized forms of RNA (tRNA and rRNA— see figure 9.8a). 2. RNA contains uracil (U), instead of thymine, as the complementary base-pairing mate for adenine. This does not change the inherent DNA code in any way because the uracil still follows the pairing rules.

2) ____ break the hydrogen bonds holding the two strands together, resulting in two separate strands. Single-stranded binding _____ keep the strands apart.

2) HELICASES break the hydrogen bonds holding the two strands together, resulting in two separate strands. Single-stranded binding PROTEINS keep the strands apart.

(The arrangement of nitrogenous bases in DNA has two essential effects:) 2. Providing VARIETY. The order of bases along the length of the DNA strand constitutes the genetic program, or the ________, of the DNA code.

2. Providing VARIETY. The order of bases along the length of the DNA strand constitutes the genetic program, or the language, of the DNA code. The message present in a gene is a precise sequence of these bases, and the genome is the collection of all DNA bases that, in an ordered combination, are responsible for the unique qualities of each organism.

3) ________ adds nucleotides in accordance with the template pattern. Note that RNA primase will have already added a short length of RNA.

3) DNA polymerase III adds nucleotides or bases in accordance with the template pattern. Note that RNA primase will have already added a short length of RNA.

3. Although RNA, like DNA, contains a _____ that consists of alternating sugar and phosphate molecules, the sugar in RNA is _____ rather than _____ose.

3. Although RNA, like DNA, contains a backbone that con- sists of alternating sugar and phosphate molecules, the sugar in RNA is RIBOSE rather than DEOXYRIBOSE.

4) Because DNA polymerase is correctly oriented for synthesis only in the 5′ to 3′ direction of the new molecule (red) strand, only one strand, called the _______ strand, can be synthesized as a continuous, complete strand.

4) Because DNA polymerase is correctly oriented for synthesis only in the 5′ to 3′ direction of the new molecule (red) strand, only one strand, called the LEADING strand, can be synthesized as a continuous, complete strand.

TRANSLATION

A _____ mutation occurs when a gene that has undergone mutation reverses (mutates back) to its original base composition.

A BACK-mutation occurs when a gene that has undergone mutation reverses (mutates back) to its original base composition.

The ribosome shifts its "reading frame" to the right along the mRNA from one codon to the next. This brings the next codon into place on the ribosome and makes a space for the next tRNA to enter the A position. A _____ bond is formed between the amino acids on the adjacent tRNAs, and the polypeptide grows in length.

A PEPTIDE BOND is formed between the amino acids on the adjacent tRNAs, and the polypeptide grows in length.

A _____ mutation (table 9.5c) alters a base but does not change the amino acid and thus has no effect. For example, because of the redundancy of the code, ACU, ACC, ACG, and ACA all code for _____, so a mutation that changes only the last base will not alter the sense of the message in any way.

A SILENT mutation (table 9.5c) alters a base but does not change the amino acid and thus has no effect. For example, because of the redundancy of the code, ACU, ACC, ACG, and ACA all code for THREONINE, so a mutation that changes only the last base will not alter the sense of the message in any way.

A eukaryotic gene contains the code for a protein, complex but located along the gene are one to several intervening sequences of bases, called _____, that do not code for protein.

A eukaryotic gene contains the code for a protein, complex but located along the gene are one to several intervening sequences of bases, called INTRONS, that do not code for protein.

A fine but important point about the lac operon is that it functions only in the absence of ______ or if the cell's energy needs are not being met by the available _____.

A fine but important point about the lac operon is that it functions only in the absence of GLUCOSE or if the cell's energy needs are not being met by the available GLUCOSE.

A microorganism that exhibits a natural, nonmutated characteristic is known as a _____ type, or _____ strain with respect to that trait.

A microorganism that exhibits a natural, nonmutated characteristic is known as a WILD type, or WILD strain with respect to that trait. You may ask, In a constantly changing population of microbes, what is the natural, non-mutated state?

A nonsense mutation almost always results in a nonfunctional protein. (Table 9.5d shows a nonsense muta- tion resulting from a frameshift, which is described in the next paragraph.)

A nonsense mutation, on the other hand, changes a normal codon into a stop codon that does not code for an amino acid and stops the production of the protein wherever it occurs.

A ribosome serves as the stage for _____

A ribosome serves as the stage for protein synthesis (from p244 Photo)

A type of TE called a ______ can transcribe DNA into RNA and then back into DNA for insertion in a new location. Other TEs contain additional genes that provide traits such as antibiotic resistance or toxin production.

A type of TE called a RETROTRANSPONON can transcribe DNA into RNA and then back into DNA for insertion in a new location. Other TEs contain additional genes that provide traits such as antibiotic resistance or toxin production.

Cause frameshifts due to insertion between base pairs

Acridine dyes

Actinomycin D binds to bacterial DNA and halts mRNA chain elongation, but it also binds to human DNA. For this reason, it is very toxic and never used to treat bacterial infections, though it can be applied in _____ treatment.

Also, in codons such as leucine, only the first two nucleotides are required to encode the correct amino acid, and the third nucleotide does not change its sense. This property, called _____, is thought to permit some variation or mutation without altering the message.

Also, in codons such as leucine, only the first two nucleotides are required to encode the correct amino acid, and the third nucleotide does not change its sense. This property, called WOBBLE, is thought to permit some variation or mutation without altering the message.

Although animal testing has been a standard method of detecting chemicals with carcinogenic potential, a more rapid screening system called the _____ test is also commonly used.

Although animal testing has been a standard method of detecting chemicals with carcinogenic potential, a more rapid screening system called the Ames test is also commonly used.

Although most of the genome exists in the form of _______, genetic material can appear in nonchromosomal sites as well

Although most of the genome exists in the form of CHROMOSOMES, genetic material can appear in nonchromosomal sites as well

_______ (such as streptomycin) inhibit peptide initiation and elongation.

Aminoglycosides (such as streptomycin) inhibit peptide initiation and elongation.

An equally important part of this concept is that EACH triplet represents a code for a particular ______. When the triplet code is transcribed and translated, it dictates the type and order of amino acids in a polypeptide (protein) chain.

An equally important part of this concept is that each triplet represents a code for a particular AMINO ACID. When the triplet code is transcribed and translated, it dictates the type and order of amino acids in a polypeptide (protein) chain.

An event in which one bacterium donates DNA to another bacterium is a type of genetic transfer termed _______, the end result of which is a new strain different from both the donor and the original recipient strain.

An event in which one bacterium donates DNA to another bacterium is a type of genetic transfer termed recombination, the end result of which is a new strain different from both the donor and the original recipient strain.

An important difference between plasmids and fragments is that while _____ has its own origin of replication and is stably replicated and inherited, chromosomal fragments must integrate themselves into the bacterial chromosome in order to be replicated and eventually passed to progeny cells.

An important difference between plasmids and fragments is that while a PLASMID has its own origin of replication and is stably replicated and inherited, CHROMOSOMAL FRAGMENTS must integrate themselves into the bacterial chromosome in order to be replicated and eventually passed to progeny cells.

Transposable Elements Another type of genetic transfer of great interest involves ______, or transposable elements (TEs). TEs have the distinction of shifting from one part of the genome to another and so are termed "jumping genes."

Another type of genetic transfer of great interest involves TRANSPOSONS, or TRANSPOSABLE ELEMENTS (TEs). TEs have the distinction of shifting from one part of the genome to another and so are termed "jumping genes."

Antisense RNAs, micro RNAs, and riboswitches (see Insight 9.2) provide regulation in many kinds of cells. But bacteria and archaea have an additional strategy: They organize collections of genes into ______.

Any change in the code that leads to placement of a different ______ is called a MISSENSE mutation.

Any change in the code that leads to placement of a different AMINO acid is called a MISSENSE mutation.

Any change to the nucleotide sequence in the genome is called a _____.

Any change to the nucleotide sequence in the genome is called a MUTATION. Mutations are most noticeable when the genotypic change leads to a change in phenotype.

Genetic exchanges have tremendous effects on the genetic diversity of bacteria. They provide additional genes for resistance to drugs and metabolic poisons, new nutritional and metabolic capabilities, and increased virulence and adaptation to the environment. In general, any organism that contains (and expresses) genes that originated in another organism is called a ______.

Any organism that contains (and expresses) genes that originated in another organism is called a RECOMBINANT

Transfer in Bacteria:: Any transfer of DNA that results in organisms acquiring new genes that did not come directly from parent organisms is called ______. Acquiring genes from parent organisms during reproduction is _______.

Any transfer of DNA that results in organisms acquiring new genes that did not come directly from parent organisms is called HORIZONTAL GENE TRANSFER. Acquiring genes from parent organisms during reproduction is VERTICAL GENE TRANSFER.

As elongation continues, the part of DNA already transcribed is rewound into its original helical form. At termination, the polymerases recognize another code that signals the separation and release of the mRNA strand, also called the ______.

As the DNA helix unwinds, the RNA polymerase first pulls the early parts of the DNA into itself, a process called "______," and then, having acquired energy from the scrunching process, begins to advance down the DNA strand to continue synthesizing an RNA molecule complementary to the template strand of DNA.

As the DNA helix unwinds, the RNA polymerase first pulls the early parts of the DNA into itself, a process called "DNA scrunching," and then, having acquired energy from the scrunching process, begins to advance down the DNA strand to continue synthesizing an RNA molecule complementary to the template strand of DNA.

As the cell's metabolism begins to slow down, however, the synthesized arginine will no longer be used up and will accumulate. The free arginine is then available to act as a corepressor by attaching to the repressor. This reaction changes the shape of the repressor, making it capable of binding to the ______. Transcription stops; arginine is no longer synthesized (figure 9.19b).

As the cell's metabolism begins to slow down, however, the synthesized arginine will no longer be used up and will accumulate. The free arginine is then available to act as a corepressor by attaching to the repressor. This reaction changes the shape of the repressor, making it capable of binding to the OPERATOR Transcription stops; arginine is no longer synthesized (figure 9.19b).

Transduction: The Case of the Piggyback DNA: _______ (bacterial viruses) have been previously described as destructive bacterial parasites. _____[ can in fact serve as genetic vectors (an entity that can bring foreign DNA into a cell).

BACTERIOPHAGES (bacterial viruses) have been previously described as destructive bacterial parasites. VIRUSES can in fact serve as genetic vectors (an entity that can bring foreign DNA into a cell).

Because the origin of replication is ____-rich, less energy is required to separate the two strands than would be required if the origin were rich in guanine and cytosine.

Because the origin of replication is AT-rich, less energy is required to separate the two strands than would be required if the origin were rich in guanine and cytosine.

______ requires the attachment of two related species and the formation of a bridge that can transport DNA.

CONJUGATION requires the attachment of two related species and the formation of a bridge that can transport DNA.

_____, _____, and _____ bind to the ribosome in a way that blocks the elongation of the polypeptide.

Chloramphenicol, lincomycin, and tetracycline bind to the ribosome in a way that blocks the elongation of the polypeptide.

Coming out of chapter 8, we should point out that the production of new DNA, RNA, and proteins is an example of an anabolic process. (Catabolic or anabolic)

Coming out of chapter 8, we should point out that the production of new DNA, RNA, and proteins is an example of an ANABOLIC process.

Conjugation: Bacterial "Sex": Conjugation is a mode of genetic exchange in which a plasmid or other genetic material is transferred by a donor to a recipient cell via a direct connection (figure 9.20). Both gram-_____ and gram-_____ cells can conjugate.

Conjugation is a mode of genetic exchange in which a plasmid or other genetic material is transferred by a donor to a recipient cell via a direct connection (figure 9.20). Both gram-negative and gram-positive cells can conjugate.

Removing primer, closing gaps, repairing mismatches

DNA polymerase I

DNA polymerase _____ removes the RNA primers used to initiate DNA synthesis and replaces them with DNA. When the forks come full circle and meet, ______ move along the lagging strand to begin the initial linking of the fragments.

DNA polymerase I removes the RNA primers used to initiate DNA synthesis and replaces them with DNA. When the forks come full circle and meet, LIGASES move along the lagging strand to begin the initial linking of the fragments.

Adding bases to the new DNA chain; proofreading the chain for mistakes

DNA polymerase III

DNA polymerase ______, the enzyme that elongates the molecule, can detect incorrect, unmatching bases; excise them; and replace them with the correct base. DNA polymerase ____ can also proof-read the molecule and repair damaged DNA.

DNA polymerase III, the enzyme that elongates the molecule, can detect incorrect, unmatching bases; excise them; and replace them with the correct base. DNA polymerase I can also proof-read the molecule and repair damaged DNA.

DNA that has been damaged by ULTRAVIOLET radiation can be restored by ______, or light repair. This repair mechanism requires visible light and a light-sensitive enzyme, ______, which can detect and attach to the damaged areas (sites of abnormal pyrimidine binding).

DNA that has been damaged by ultraviolet radiation can be restored by PHOTOACTIVATION, or light repair. This repair mechanism requires visible light and a light-sensitive enzyme, DNA PHOTOLYASE, which can detect and attach to the damaged areas (sites of abnormal pyrimidine binding).

DNA to RNA is ____. RNA to protein is ______.

DNA to RNA is transcription. RNA to protein is translation.

DNA transfer between bacterial cells typically involves small pieces of DNA in the form of ______ or ______.

DNA transfer between bacterial cells typically involves small pieces of DNA in the form of PLASMIDS or CHROMOSOMAL FRAGMENTS.

Depending on the mode of transmission, the means of genetic recombination in bacteria is called ______, ______, or _____.

Depending on the mode of transmission, the means of genetic recombination in bacteria is called CONJUGATION, TRANSFORMATION, or TRANSDUCTION.

Drugs that inhibit protein synthesis exert their influence on transcription or translation. For example, the _____ used in therapy for tuberculosis bind to RNA polymerase, blocking the initiation step of transcription, and are selectively more active against bacterial RNA polymerase than the corresponding eukaryotic enzyme.

Drugs that inhibit protein synthesis exert their influence on transcription or translation. For example, the RIFAMYCINS used in therapy for tuberculosis bind to RNA polymerase, blocking the initiation step of transcription, and are selectively more active against bacterial RNA polymerase than the corresponding eukaryotic enzyme.

Due to the structure of eukaryotic DNA and the unidirectional action of DNA polymerase, the 3′ end of DNA molecules cannot be completely copied. These areas, called ______, begin to erode with each cell division.

Due to the structure of eukaryotic DNA and the unidirectional action of DNA polymerase, the 3′ end of DNA molecules cannot be completely copied. These areas, called TELOMERES, begin to erode with each cell division.

During replication, _____ unwind the DNA helix, giving access to helicases (unzipping enzymes) to bind to the dsDNA at the origin.

During replication, TOPOISOMERASES unwind the DNA helix, giving access to helicases (unzipping enzymes) to bind to the dsDNA at the origin.

Transcription: The First Stage of Gene Expression: During transcription, the DNA code is converted to RNA through several stages, directed by a huge and very complex enzyme system called ______. Process figure 9.12 supplies the details you will need to know about transcription.

During transcription, the DNA code is converted to RNA through several stages, directed by a huge and very complex enzyme system called RNA polymerase. Process figure 9.12 supplies the details you will need to know about transcription.

Each NUCLEOTIDE is composed of _____, _____ sugar, and a _____ base.

Each NUCLEOTIDE is composed of phosphate, deoxyribose sugar, and a nitrogenous base.

Each circular DNA molecule will have ______(#) replication forks (only one is shown in process figure 9.6).

Each circular DNA molecule will have 2 (#) replication forks (only one is shown in process figure 9.6).

(Step 2>>) ______ begins when the A site is filled by the second tRNA. The identity of this tRNA and its amino acid is dictated by the SECOND mRNA codon. (FMet is the first amino acid and is only there to join the next amino acid to form a peptide bond)

Elongation begins begins when the A site is filled by the second tRNA. The identity of this tRNA and its amino acid is dictated by the second mRNA codon. (FMet is the first amino acid and is only there to join the next amino acid to form a peptide bond)

Elongation: During elongation, which proceeds in the 5′ to 3′ direction (with regard to the growing RNA molecule), the mRNA is assembled by the addition of nucleotides that are complementary to the DNA template. Remember that uracil (U) is placed as adenine's complement. As elongation continues, the part of DNA already transcribed is rewound into its original helical form.

Encapsulated strains have a _____ colony appearance and are virulent; strains lacking a capsule have a _____ appearance and are nonvirulent.

Encapsulated strains have a SMOOTH (S) colony appearance and are virulent; strains lacking a capsule have a ROUGH (R) appearance and are nonvirulent.

Inserts between the paired bases

Ethidium bromide

Eukaryotic chromosomes are located in the nucleus; they vary in number from a few to hundreds; they can occur in pairs or ____ or singles or ____; and they have a linear appearance.

Eukaryotic chromosomes are located in the nucleus; they vary in number from a few to hundreds; they can occur in pairs or DIPLOIDS or singles or HAPLOIDS and they have a linear appearance.

Cotranscriptional translation occurs in all three, eukaryotes, bacteria and archeae.

False; Cotranscriptional translation only occurs in bacteria and archaea, because there is no nucleus and transcription and translation both occur in the cytoplasm. (In eukaryotes, transcription occurs in the nucleus.)

First, enzymes break the bonds between the bases and the sugar-phosphate strand at the site of the error. A different enzyme subsequently removes the defective bases one at a time, leaving a gap that will be filled in by _____ and ____ (figure 9.26).

For that reason, most scientists prefer to define wild type as the trait present in the highest numbers in a population. If a microorganism bears a mutation, it is called a ______ strain.

For that reason, most scientists prefer to define wild type as the trait present in the highest numbers in a population. If a microorganism bears a mutation, it is called a MUTANT strain.

(Step 6>>) For the next step to proceed, some room must be made on the ribosome, and the next codon in sequence must be brought into position for reading. This process is accomplished by _____, the enzyme-directed shifting of the ribosome to the right along the mRNA strand, which causes the blank tRNA 1 to be discharged from the ribosome at the E site.

For the next step to proceed, some room must be made on the ribosome, and the next codon in sequence must be brought into position for reading. This process is accomplished by TRANSLOCATION, the enzyme-directed shifting of the ribosome to the right along the mRNA strand, which causes the blank tRNA 1 to be discharged from the ribosome at the E site.

_____ is the study of the inheritance, or heredity, of living things.

GENETICS is the study of the inheritance, or heredity, of living things.

_____ is the study of an organism's entire genome; research in this area has grown exponentially over the past 10 years, leading to new discov- eries about microbial evolution, ecology, and pathogenesis.

GENOMICS is the study of an organism's entire genome; research in this area has grown exponentially over the past 10 years, leading to new discoveries about microbial evolution, ecology, and pathogenesis.

Genes fall into three basic categories: (1) ______ genes that code for proteins, (2) genes that code for the ____ machinery used in protein production, and (3) ______ genes that *control gene expression.

Genes fall into three basic categories: (1) STRUCTURAL genes that code for proteins, (2) genes that code for the RNA machinery used in protein production, and (3) REGULATORY genes that *control gene expression.

Unzipping the DNA helix .

Helicase

In ______ transduction (process figure 9.23), random fragments of disintegrating host DNA are taken up by the phage during assembly.

In GENERALIZED transduction (process figure 9.23), random fragments of disintegrating host DNA are taken up by the phage during assembly.

In ______ transduction (process figure 9.24), a highly specific part of the host genome is regularly incorporated into the virus. This specificity is explained by the prior existence of a temperate prophage inserted in a fixed site on the bacterial chromosome.

In SPECIALIZED transduction (process figure 9.24), a highly specific part of the host genome is regularly incorporated into the virus. This specificity is explained by the prior existence of a temperate prophage inserted in a fixed site on the bacterial chromosome.

In classical genetics, the term _____ refers to the fundamental unit of heredity responsible for a given trait in an organism.

In classical genetics, the term GENE refers to the fundamental unit of heredity responsible for a given trait in an organism.

In eukaryotic cells, gene function can be altered by intrinsic regulatory segments similar to operons. Some molecules, called _____, insert on the grooves of the DNA molecule and enhance transcription of specific genes.

In eukaryotic cells, gene function can be altered by intrinsic regulatory segments similar to operons. Some molecules, called TRANSCRIPTION FACTORS, insert on the grooves of the DNA molecule and enhance transcription of specific genes.

In fact, the language of DNA exists in the order of groups of "three consecutive bases" called ______ on one DNA strand (figure 9.9).

In fact, the language of DNA exists in the order of groups of three consecutive bases called TRIPLETS on one DNA strand (figure 9.9). Thus, one gene differs from another in its composition of triplets.

In general, a ______ is a discrete cellular structure composed of a neatly packaged DNA molecule. The chromosomes of eukaryotes and bacterial cells differ in several respects.

In general, a CHROMOSOMES is a discrete cellular structure composed of a neatly packaged DNA molecule. The chromosomes of eukaryotes and bacterial cells differ in several respects.

In gram-negative cells, the donor has a plasmid known as the _____ factor that allows the synthesis of a conjugative pilus.

In gram-negative cells, the donor has a plasmid known as the FERTILITY (F) factor that allows the synthesis of a conjugative pilus.

In inducible systems like the lac operon, the operon is normally in an off mode and does not initiate transcription when the appropriate substrate is absent (process figure 9.18). How is the operon maintained in this mode? The key is in the ______ protein that is coded by the regulatory gene. This relatively large molecule is allosteric, meaning it has two binding sites, one for the operator sequence on the DNA and another for lactose.

In inducible systems like the lac operon, the operon is normally in an off mode and does not initiate transcription when the appropriate substrate is absent (process figure 9.18). How is the operon maintained in this mode? The key is in the REPRESSOR protein that is coded by the regulatory gene. This relatively large molecule is ALLOSTERIC, meaning it has two binding sites, one for the operator sequence on the DNA and another for lactose.

The Nature of the Genetic Material For a species to survive, it must have the capacity of self-replication. In single-celled microorganisms, reproduction usually involves the division of the cell by means of ______ or _______ and the accurate duplication and separation of genetic material into each daughter cell.

In single-celled microorganisms, reproduction usually involves the division of the cell by means of BINARY FISSION or BUDDING and the accurate duplication and separation of genetic material into each daughter cell.

In the absence of lactose, this ______ binds to the operator locus, thereby "blocking the transcription of the structural genes lying downstream". Think of the repressor as a lock on the operator, and if the operator is locked, the structural genes cannot be transcribed. Importantly, the regulator gene lies upstream (to the left) of the operator region and is transcribed constitutively because it is not controlled in tandem with the operon.

In the absence of lactose, this repressor binds to the operator locus, thereby blocking the transcription of the structural genes lying downstream. Think of the repressor as a lock on the operator, and if the operator is locked, the structural genes cannot be transcribed. Importantly, the regulator gene lies upstream (to the left) of the operator region and is transcribed constitutively because it is not controlled in tandem with the operon.

In the molecular and biochemical sense, the _____ is a site on the chromosome that provides information for a certain cell function.

In the molecular and biochemical sense, the GENE is a site on the chromosome that provides information for a certain cell function.

_____ mutations result from exposure to known mutagens, which are primarily physical or chemical agents that interact with DNA in a disruptive manner (table 9.4). Chemical mutagenic agents act in a variety of ways to change the DNA.

Induced mutations result from exposure to known mutagens, which are primarily physical or chemical agents that interact with DNA in a disruptive manner (table 9.4). Chemical mutagenic agents act in a variety of ways to change the DNA.

What are the 3 steps of transcription?

Initiation, Elongation, Termination

Initiation: Transcription is initiated when RNA polymerase recognizes a segment of the DNA called the _____ region. This region consists of two sequences of DNA just prior to the beginning of the gene to be transcribed.

Initiation. Transcription is initiated when RNA polymerase recognizes a segment of the DNA called the PROMOTER region. This region consists of two sequences of DNA just prior to the beginning of the gene to be transcribed.

Introns are interspersed between coding regions, called _____, that will be translated into protein (figure 9.17). We can use words as examples.

Introns are interspersed between coding regions, called EXONs, that will be translated into protein (figure 9.17). We can use words as examples.

Radiation: Form free radicals that cause single or double breaks in DNA

Ionizing/gamma rays, X rays

James ____ and Francis ____ put the pieces of the puzzle together in 1953 to discover that DNA is a gigantic molecule, a type of _____(organic molecule), with two strands combined into a double helix.

James Watson and Francis Crick put the pieces of the puzzle together in 1953 to discover that DNA is a gigantic molecule, a type of nucleic acid, with two strands combined into a double helix.

Just as a person inherits a gene combination (genotype) that gives a certain eye color or height (phenotype), a ______ inherits genes that direct the formation of a FLAGELLUM, and a _____ contains genes for its CAPSID structure.

Just as a person inherits a gene combination (genotype) that gives a certain eye color or height (phenotype), a bacterium inherits genes that direct the formation of a flagellum, and a virus contains genes for its capsid structure.

Final binding of nicks in DNA during synthesis and repair

Ligase

Many catabolic operons, or operons encoding enzymes that act in catabolism, are ______, meaning that the operon is turned on by the substrate of the enzyme(s) for which the structural genes code.

Many catabolic operons, or operons encoding enzymes that act in catabolism, are INDUCIBLE, meaning that the operon is turned on (induced) by the substrate of the enzyme(s) for which the structural genes code.

More precisely, it states that the master code of DNA is first used to synthesize an RNA molecule via a process called _______, and the information contained in the RNA is then used to produce proteins in a process known as ______.

More precisely, it states that the master code of DNA is first used to synthesize an RNA molecule via a process called TRANSCRIPTION, and the information contained in the RNA is then used to produce proteins in a process known as TRANSLATION.

Most viruses contain normal double-stranded (ds) DNA or single-stranded (ss) RNA, but other patterns exist. There are ssDNA viruses, dsRNA viruses, and retroviruses, which work backward by making dsDNA from ssRNA.

Most viruses contain normal double-stranded (ds) DNA or single- stranded (ss) RNA, but other patterns exist. There are ssDNA viruses, dsRNA viruses, and retroviruses, which work backward by making dsDNA from ssRNA.

If not corrected, they are referred to as _____ (covered later in this chapter). Because continued cellular integrity is very dependent on accurate replication, cells have evolved their own proofreading function for DNA.

Mutations

Mutations also occur when one or more bases are inserted into or deleted from a newly synthesized DNA strand. This type of mutation, known as a _____ (table 9.5d,e), is so named because the reading frame of the mRNA has been changed.

Mutations also occur when one or more bases are inserted into or deleted from a newly synthesized DNA strand. This type of mutation, known as a FRAMESHIFT (table 9.5d,e), is so named because the reading frame of the mRNA has been changed.

Mutations can be excised by a series of enzymes that remove the incorrect bases and add the correct ones. This process is known as ______ repair.

Mutations can be excised by a series of enzymes that remove the incorrect bases and add the correct ones. This process is known as EXCISION repair.

Next, a type of RNA and protein called a ______ recognizes the exon-intron junctions and enzymatically cuts through them.

Next, a type of RNA and protein called a SPLICEOSOME recognizes the exon-intron junctions and enzymatically cuts through them.

Compete with natural bases for sites on replicating DNA

Nitrogen base analogs

Chemical Remove an amino group from some bases

Nitrous acid, bisulfite

______ genetics observes the heredity of the whole organism or cell _______ genetics examines the characteristics and actions of chromosomes ______ genetics deals with the biochemistry of the genes.

ORGANISMAL genetics observes the heredity of the whole organism or cell CHROMOSOMAL genetics examines the characteristics and actions of chromosomes MOLECULAR genetics deals with the biochemistry of the genes.

The short segments of DNA synthesized in a 5′ to 3′ direction, which are then sealed together to form a 3′ to 5′ strand.

Okazaki fragments

Once they shorten to a certain length, they will trigger cell death or ______. In this way, the problem of end replication also provides a beneficial mechanism for older cells to be removed in higher eukaryotes.

Once they shorten to a certain length, they will trigger cell death or APOPTOSIS.

One group of antibiotics, including _____ and _____, prevents translation by interfering with the attachment of mRNA to ribosomes.

One group of antibiotics, including erythromycin and spectinomycin, prevents translation by interfering with the attachment of mRNA to ribosomes.

One of the bonds is to the number ___′ (read "five prime") carbon on deoxyribose, and the other is to the ___′ carbon, which confers a certain order and direction on each strand (figure 9.4).

One of the bonds is to the number 5′ (read "five prime") carbon on deoxyribose, and the other is to the 3′ carbon, which confers a certain order and direction on each strand (figure 9.4).

One of the enzymes, ______, hydrolyzes the lactose into its monosaccharides; another, ______, brings lactose across the cell membrane. The third enzyme is an ______ that helps in the metabolism of lactose.

One of the enzymes, β-galactosidase, hydrolyzes the lactose into its monosaccharides; another, PERMEASE, brings lactose across the cell membrane. The third enzyme is an ACETYLTRANSFERASE that helps in the metabolism of lactose.

Only one strand of the DNA—the TEMPLATE strand—contains meaningful instructions for synthesis of a functioning polypeptide or protein.

Only one strand of the DNA—the ______ strand—contains meaningful instructions for synthesis of a functioning polypeptide. The strand of DNA that serves as a template varies from one gene to another.

Operons consist of a coordinated set of genes, all of which are regulated as a single unit. Operons are described as either _____ or _____. The category each operon falls into is determined by how transcription is affected by the environment surrounding the cell.

Operons consist of a coordinated set of genes, all of which are regulated as a single unit. Operons are described as either INDUCIBLE or REPRESSIBLE. The category each operon falls into is determined by how transcription is affected by the environment surrounding the cell.

Operons consist of a coordinated set of genes, all of which are regulated as a single unit. Operons are described as either INDUCTIVE or REPRESSIVE. The category each operon falls into is determined by how _____ is affected by the _____ surrounding the cell.

Operons consist of a coordinated set of genes, all of which are regulated as a single unit. Operons are described as either INDUCTIVE or REPRESSIVE. The category each operon falls into is determined by how transcription is affected by the environment surrounding the cell.

Completion of Protein Synthesis Before newly made proteins can carry out their structural or enzymatic roles, they often require finishing touches. Even before the peptide chain is released from the ribosome, it begins folding upon itself to achieve its biologically active tertiary conformation. Other alterations, called _____ modifications, may be necessary.

Other alterations, called POSTTRANSLATIONAL modifications, may be necessary.

Other important considerations of DNA structure concern the nature of the double helix itself. The halves are not oriented in the same direction. One side of the helix runs in the opposite direction of the other, in what is called an _______ arrangement (figure 9.4b).

_____ are small, circular pieces of DNA that contain their own origin of replication and therefore can replicate independently of the bacterial chromosome.

Plasmids are small, circular pieces of DNA that contain their own origin of replication and therefore can replicate independently of the bacterial chromosome.

The action of this splicer enzyme loops the introns into lariat-shaped pieces, excises them, and joins the exons end to end. By this means, a strand of mRNA with no intron material is produced.

Pretty the spliceosome gets rid of the introns in an mRNA

Synthesizing an RNA primer

Primase

An RNA that can "begin" DNA replication

Primer

Expression of DNA for structures and functions of cell

Protein

The operation of transcription and translation is machine-like in its precision. Protein synthesis in bacteria is both efficient and rapid, as the translation of mRNA starts while transcription is still occurring (figure 9.16), a process called ______.

Protein synthesis in bacteria is both efficient and rapid, as the translation of mRNA starts while transcription is still occurring (figure 9.16), a process called COTRANSCRIPTIONAL TRANSLATION.

Recombination in bacteria depends in part on the fact that bacteria contain extrachromosomal DNA—that is, ______—and are adept at moving between cells.

Recombination in bacteria depends in part on the fact that bacteria contain extrachromosomal DNA—that is, plasmids—and are adept at moving between cells.

Micro (miRNA), antisense, riboswitch, and small interfering (siRNA)

Regulatory RNA

Regulates gene expression and cooling of chromatin

Regulatory RNA

The place in the helix where the strands are unwound and replication is taking place.

Replication fork

Repressible operons often contain genes coding for _____ enzymes, such as those used to synthesize amino acids. In the case of these operons, several genes in series are turned off (repressed) by the product synthesized by the enzyme.

Repressible operons often contain genes coding for ANABOLIC enzymes, such as those used to synthesize amino acids. In the case of these operons, several genes in series are turned off (repressed) by the product synthesized by the enzyme.

RNA enzymes, parts of splicer enzymes and removes introns from other RNAs in eukaryotes

Ribozymes and spliceosomes

Step 2 (Translation): Rules of pairing dictate that the anticodon of this tRNA must be complementary to the mRNA codon AUG; thus, the tRNA with anticodon UAC will first occupy site P. It happens that the amino acid carried by the "initiator tRNA" in bacteria is ______.

Rules of pairing dictate that the anticodon of this tRNA must be complementary to the mRNA codon AUG; thus, the tRNA with anticodon UAC will first occupy site P. It happens that the amino acid carried by the initiator tRNA in bacteria is FORMYL METHIONINE or fMET.

_____ codon The first three RNA nucleotides that signal the beginning of the message. The start codon is always ____. _____ codon One of three codons—____, ____, or _____— that has no corresponding tRNA and therefore causes translation to be terminated; also called nonsense codon.

START codon The first three RNA nucleotides that signal the beginning of the message. The start codon is always AUG. STOP codon One of three codons—UAA, UAG, or UGA— that has no corresponding tRNA and therefore causes translation to be terminated; also called nonsense codon.

Some mutations have a harmful effect on the cell, leading to cell dysfunction or death; these are called _____ mutations. _____ mutations produce neither adverse nor helpful changes. Of course, mutations can also be beneficial if they provide the cell with a useful change in structure or physiology.

Some mutations have a harmful effect on the cell, leading to cell dysfunction or death; these are called LETHAL mutations. NEUTRAL mutations produce neither adverse nor helpful changes. Of course, mutations can also be beneficial if they provide the cell with a useful change in structure or physiology.

Pathogenicity Islands: Special "Gifts" of Horizontal Gene Transfer?: Some of the horizontally transferred genes in bacteria have the ability to make their new hosts pathogenic, or able to cause disease. These are termed ______ (PAIs).

Some of the horizontally transferred genes in bacteria have the ability to make their new hosts pathogenic, or able to cause disease. These are termed PATHOGENICITY ISLANDS (PAIs).

AUG means what?

Start

TEs contain DNA that codes for the enzymes needed to remove and reintegrate the TE at another site in the genome. Flanking the coding region of the DNA are sequences called ______, which mark the point at which the TE is removed or reinserted into the genome.

TEs contain DNA that codes for the enzymes needed to remove and reintegrate the TE at another site in the genome. Flanking the coding region of the DNA are sequences called TANDEM REPEATS, which mark the point at which the TE is removed or reinserted into the genome.

________ then causes a double-stranded DNA break that allows for the completion of synthesis and the separation of the intertwined circles into two fully replicated daughter molecules (figure 9.7b).

TOPOISOMERASE IV then causes a double-stranded DNA break that allows for the completion of synthesis and the separation of the intertwined circles into two fully replicated daughter molecules. (figure 9.7b).

______ are utilized in replication to relieve the tension on the DNA as it is copied but also to recompact the DNA when the molecule is completely replicated.

TOPOISOMERASE are utilized in replication to relieve the tension on the DNA as it is copied but also to recompact the DNA when the molecule is completely replicated.

The Major Participants in Transcription and Translation: ______, the formation of RNA using DNA as a template, and ______, the synthesis of proteins using RNA as a template, are highly complex.

TRANSCRIPTION, the formation of RNA using DNA as a template, and TRANSLATION, the synthesis of proteins using RNA as a template, are highly complex.

_____ entails the transfer of naked DNA and requires no special vehicle. _____ is DNA transfer mediated through the action of a bacterial virus (table 9.3).

TRANSFORMATION entails the transfer of naked DNA and requires no special vehicle. TRANSDUCTION is DNA transfer mediated through the action of a bacterial virus (table 9.3).

The DNA is then processed by the cell membrane and transported into the cytoplasm, where some of it is inserted into the bacterial chromosome. Transformation is a _____ event found in several groups of gram-positive and gram-negative bacterial species.

TRANSFORMATION is a NATURAL event found in several groups of gram-positive and gram-negative bacterial species.

______: The process of shifting the ribosome down the mRNA strand to read new codons.

TRANSLOCATION: The process of shifting the ribosome down the mRNA strand to read new codons.

______ codons—____, ____, and ____—are codons for which there is no corresponding tRNA. Although they are often called nonsense codons, they carry a necessary and useful message: Stop here.

Termination codons—UAA, UAG, and UGA—are codons for which there is no corresponding tRNA. Although they are often called nonsense codons, they carry a necessary and useful message: Stop here.

Termination: At termination, the polymerases recognize another code that signals the separation and release of the mRNA strand, or _____.

Termination: At termination, the polymerases recognize another code that signals the separation and release of the mRNA strand, or TRANSCRIPT.

(Cont on Figure 9.5) The DNA polymerases not only are important for DNA replication and making two identical DNA strands, but they attach the correct ______ to the template pattern on the helix.

The DNA polymerases not only are important for DNA replication and making two identical DNA strands, but they attach the correct NUCLEOTIDE to the template pattern on the helix.

The DNA probably does not pass through the pilus—that structure is used to bring the cells in contact. The actual transfer takes place through membrane secretion systems. Conjugation is a ______ process, in that the donor bacterium generally retains ("conserves") a copy of the genetic material being transferred.

The DNA probably does not pass through the pilus—that structure is used to bring the cells in contact. The actual transfer takes place through membrane secretion systems. Conjugation is a CONSERVATIVE process, in that the donor bacterium generally retains ("conserves") a copy of the genetic material being transferred.

The F factor can direct a more comprehensive transfer of part of the donor chromosome to a recipient cell. This transfer occurs through duplication of the DNA, after which one strand of DNA is retained by the donor, and the other strand is transported across to the recipient cell.

The Levels of Structure and Function of the Genome The _____ is the sum total of genetic material of an organism.

The GENOME is the sum total of genetic material of an organism.

Transformation: Capturing DNA from Solution The acceptance by a bacterial cell of small fragments of soluble DNA from the surrounding environment is termed ______ (figure 9.21). Cells that are capable of accepting genetic material through this means are termed ______.

The acceptance by a bacterial cell of small fragments of soluble DNA from the surrounding environment is termed TRANSFORMATION (figure 9.21). Cells that are capable of accepting genetic material through this means are termed COMPETENT.

The bacterial (70S) RIBOSOME is a particle composed of tightly packaged ____ and ____.

The bacterial (70S) ribosome is a particle composed of tightly packaged rRNA (ribosomal) and PROTEIN.

The basic unit of DNA ("N") structure is a _____, and a chromosome in a typical bacterium consists of several million nucleotides linked.

The basic unit of DNA structure is a NUCLEOTIDE, and a chromosome in a typical bacterium consists of several million nucleotides linked end to end.

The Lactose Operon: A Model for Inducible Gene Regulation in Bacteria The best understood cell system for explaining control through genetic induction is the LACTOSE (lac) OPERON. This system, first described in 1961 by François ____ and Jacques ____, accounts for the regulation of lactose metabolism in Escherichia coli.

The best understood cell system for explaining control through genetic induction is the lactose (lac) operon. This system, first described in 1961 by François JACOB and Jacques MONOD, accounts for the regulation of lactose metabolism in Escherichia coli.

The chromosomes of all cells are subdivided into basic informational packets called _____.

The chromosomes of all cells are subdivided into basic informational packets called GENES.

Translation Step 3: The entry of tRNA 2 into the A site brings the two adjacent tRNAs in favorable proximity for a peptide bond to form between the amino acids (aa) they carry. The _____ is transferred from the first tRNA to aa 2 or second amino acid, resulting in "two" coupled amino acids called a _____.

The entry of tRNA 2 into the A site brings the two adjacent tRNAs in favorable proximity for a peptide bond to form between the amino acids (aa) they carry. The fMet is transferred from the first tRNA to aa 2 or second amino acid, resulting in two coupled amino acids called a DIPEPTIDE.

The experiment was conducted in the late 1920s by the English biochemist Frederick _____ working with _____ and laboratory MICE 🐁 . This bacterium can be found in two different forms based on the presence of a capsule—the presence or absence of which affects colony morphology and pathogenicity.

The experiment was conducted in the late 1920s by the English biochemist Frederick GRIFFITH working with STREPTOCOCCUS PNEUMONIAE and laboratory mice. This bacterium can be found in two different forms based on the presence of a capsule—the presence or absence of which affects colony morphology and pathogenicity.

The final key points that connect DNA and an organism's traits follow: 1. A protein's PRIMARY structure—the order and type of amino acids in the chain—determines its characteristic shape and function (see figures 2.21 and 2.22). 2. PROTEINS ultimately determine ___enotype, the expression of all aspects of cell function and structure. Put more simply, living things are what their proteins make them. Regulatory RNAs help determine which proteins are made. ______ is the study of an organism's complete set of expressed proteins. 3. DNA is mainly a blueprint that tells the cell which kinds of proteins and RNAs to make and how to make them.

The final key points that connect DNA and an organism's traits follow: 1. A protein's PRIMARY structure—the order and type of amino acids in the chain—determines its characteristic shape and function (see figures 2.21 and 2.22). 2. Proteins ultimately determine PHENOTYPE, the expression of all aspects of cell function and structure. Put more simply, living things are what their proteins make them. Regulatory RNAs help determine which proteins are made. PROTEOMICS is the study of an organism's complete set of expressed proteins. 3. DNA is mainly a blueprint that tells the cell which kinds of proteins and RNAs to make and how to make them.

The lactose operon has three important features (process figure 9.18): 1. the ______, composed of the gene that codes for a pro- tein capable of repressing the operon (a repressor); 2. the _______, composed of two areas, the promoter (recognized by RNA polymerase) and the operator, a sequence that acts as an on/off switch for transcription; and 3. the ______, made up of three genes, each coding for a different enzyme needed to catabolize lactose.

The lactose operon has three important features (process figure 9.18): 1. the REGULATOR, composed of the gene that codes for a protein capable of repressing the operon (a repressor); 2. the CONTROL LOCUS, composed of two areas, the PROMOTER (recognized by RNA polymerase) and the OPERATOR, a sequence that acts as an on/off switch for transcription; and 3. the STRUCTURAL LOCUS, made up of three genes, each coding for a different enzyme needed to catabolize lactose.

The many functional types of RNA range from small regulatory pieces to large structural ones (table 9.2 and Insight 9.2). All types of RNA are formed through transcription of a DNA gene, but only _____ (tRBA, rRNA, or mRNA?) is further translated into another type of molecule (protein).

The many functional types of RNA range from small regulatory pieces to large structural ones (table 9.2 and Insight 9.2). All types of RNA are formed through transcription of a DNA gene, but only "mRNA" is further translated into another type of molecule (protein).

The message of this transcribed strand is later read as a series of triplets called _____ (figure 9.10), and the length of the mRNA molecule varies from about 100 nucleotides to several thousand. The details of transcription and the function of mRNA in translation will be covered shortly.

The message of this transcribed strand is later read as a series of triplets called CODONS (figure 9.10), and the length of the mRNA molecule varies from about 100 nucleotides to several thousand. The details of transcription and the function of mRNA in translation will be covered shortly.

The message present in a gene is a precise sequence of these bases, and the ______ is the collection of all DNA bases that, in an ordered combination, are responsible for the unique qualities of each organism.

The message present in a gene is a precise sequence of these bases, and the GENOME is the collection of all DNA bases that, in an ordered combination, are responsible for the unique qualities of each organism.

The nitrogenous ______, purines and pyrimidines, attach by covalent bonds at the 1' position position of the sugar (figure 9.4a). They span the center of the molecule and pair with appropriate complementary bases from the other strand.

The nitrogenous BASES, purines and pyrimidines, attach by covalent bonds at the 1′ position of the sugar (figure 9.4a). They span the center of the molecule and pair with appropriate complementary bases from the other strand.

The nucleotide sequence of promoters differs only slightly from gene to gene, with all promoters being rich in adenine and thymine. Only one strand of DNA, called the _____ strand, is copied by RNA polymerase.

The nucleotide sequence of promoters differs only slightly from gene to gene, with all promoters being rich in adenine and thymine. Only one strand of DNA, called the TEMPLATE strand, is copied by RNA polymerase.

The nucleotides covalently bond to each other in a ______ linkage that becomes the backbone of each strand. Each sugar attaches in a repetitive pattern to ____ (#) phosphates.

The nucleotides covalently bond to each other in a SUGAR-PHOSPHATE linkage that becomes the backbone of each strand. Each sugar attaches in a repetitive pattern to 2 phosphates.

The only exceptions to this pattern are found in _____, which convert RNA to other RNA, and in ______, which convert RNA to DNA.

The only exceptions to this pattern are found in RNA viruses, which convert RNA to other RNA, and in RETROVIRUSES, which convert RNA to DNA.

The order of the bond between the carbon on DEOXYRIBOSE and the PHOSPHATES is used to keep track of the direction of the two sides of the helix. Thus, one helix runs from the 5′ to 3′ direction, and the other runs from the 3′ to 5′ direction. This characteristic is a significant factor in DNA ______ and ______ production.

The paired bases are joined by _____ bonds. Such weak bonds are easily broken, allowing the molecule to be "unzipped" into its two complementary strands. This feature is of great importance.

The paired bases are joined by HYDROGEN bonds. Such weak bonds are easily broken, allowing the molecule to be "unzipped" into its two complementary strands.

The pairing of nitrogenous bases, purines and pyrimidines is dictated by the formation of ______ binds between certain bases

The pairing of nitrogenous bases, purines and pyrimidines is dictated by the formation of HYDROGEN bonds between certain bases

The preservation of the parent molecule in this way, termed the ________ replication—semi meaning "half," as in semicircle—helps explain the reliability and fidelity of replication.

The preservation of the parent molecule in this way, termed the SEMICONSERVATIVE replication—semi meaning "half," as in semicircle—helps explain the reliability and fidelity of replication.

Refinements and Details of Replication The process of synthesizing a new daughter strand of DNA using the parental strand as a template is carried out by the enzyme DNA polymerase _____.

The process of synthesizing a new daughter strand of DNA using the parental strand as a template is carried out by the enzyme DNA polymerase III.

The _____ component of the ribosome is also a long polynucleotide molecule. It forms complex three-dimensional figures that contribute to the structure and function of ribosomes.

The rRNA component of the ribosome is also a long polynucleotide molecule. It forms complex three-dimensional figures that contribute to the structure and function of ribosomes.

The recipient cell has a recognition site on its surface. A cell's role in conjugation is denoted by F___ for the cell that has the F plasmid and by F____ for the cell that lacks it.

The recipient cell has a recognition site on its surface. A cell's role in conjugation is denoted by F1 for the cell that has the F plasmid and by F2 for the cell that lacks it.

The recognizable words are the _____, and the nonsense letters represent the _____. This unusual genetic architecture, sometimes called a _____ gene, requires further processing before translation.

The recognizable words are the EXONS, and the nonsense letters represent the INTRONS. This unusual genetic architecture, sometimes called a SPLIT gene, requires further processing before translation.

(Step 1>>) The ribosome also has an exit or ____ site where used tRNAs are released. P stands for _____ site; A stands for _____ site; E stands for exit site.

The ribosome also has an exit or E site where used tRNAs are released. P stands for PEPTIDE site; A stands for AMINO ACID site; E stands for exit site.

The ribosome begins to scan the mRNA by moving in the ___′ to ___′ direction along the mRNA. The first codon it encounters is called the START codon, which is almost always ____ (and, rarely, GUG).

The ribosome begins to scan the mRNA by moving in the 5′ to 3′ direction along the mRNA. The first codon it encounters is called the START codon, which is almost always AUG (and, rarely, GUG).

The ribosome thus recognizes these molecules and stabilizes reactions between them. The _____ subunit binds to the 5′ end of the mRNA, and the _____ subunit supplies enzymes for making peptide bonds on the protein.

The ribosome thus recognizes these molecules and stabilizes reactions between them. The SMALL subunit binds to the 5′ end of the mRNA, and the LARGE subunit supplies enzymes for making peptide bonds on the protein.

The sequence of bases in DNA is a _____.

The sequence of bases in DNA is a genetic code.

The smallest TEs consist of only these two genetic sequences and are often referred to as _______.

The smallest TEs consist of only these two genetic sequences and are often referred to as INSERTION ELEMENTS.

The step in which the complementary tRNA meets with the mRNA code is guided by the two sites on the LARGE subunit of the ribosome called the ____ site (left) and the ____ site (right).

The step in which the complementary tRNA meets with the mRNA code is guided by the two sites on the large subunit of the ribosome called the P site (left) and the A site (right).

The strand with the opposite orientation (3′ to 5′) is termed the ______ strand. On this strand the polymerase adds nucleotides a few at a time in the direction away from the fork (5′ to 3′). (Cont 4)

The strand with the opposite orientation (3′ to 5′) is termed the LAGGING strand. On this strand the polymerase adds nucleotides a few at a time in the direction away from the fork (5′ to 3′). (Cont 4)

The structural genes are transcribed in a single unbroken transcript coding for all three enzymes. (During translation, however, each protein is synthesized separately.) Because lactose is ultimately responsible for stimulating protein synthesis, it is called the _____.

The structure of EUKARYOTIC chromosomes consists of a _____ molecule tightly wound around _____, whereas a bacterial chromosome is condensed and secured into a packet by means of histonelike proteins.

The structure of eukaryotic chromosomes consists of a DNA molecule tightly wound around HISTONE proteins, whereas a bacterial chromosome is condensed and secured into a packet by means of histonelike proteins.

The sum of all of these types of genes constitutes an organism's distinctive genetic makeup, or _____. The expression of the genotype creates _____ (certain structures or functions) referred to as the _____.

The sum of all of these types of genes constitutes an organism's distinctive genetic makeup, or GENOTYPE. The expression of the genotype creates traits (certain structures or functions) referred to as the PHENOTYPE.

The term ______ was adopted to denote a cell with an integrated F factor that transmits its chromosomal genes. These genes become integrated into recipient chromosomes at a very high frequency.

The term high-frequency recombination was adopted to denote a cell with an integrated F factor that transmits its chromosomal genes. These genes become integrated into recipient chromosomes at a very high frequency.

These Okazaki fragments are attached to the growing end of the lagging strand by another enzyme called _______. (Cont 4)

These Okazaki fragments are attached to the growing end of the lagging strand by another enzyme called DNA ligase. (Cont 4)

These islands contain multiple genes that are coordinated to create a new trait on the bacterium, such as the ability to scavenge iron, the bacterium causing the plague, _____, or the ability to produce exotoxins, seen in ______. The islands are usually flanked by sequences that look like genes for TE enzymes.

These islands contain multiple genes that are coordinated to create a new trait on the bacterium, such as the ability to scavenge IRON, the bacterium causing the PLAGUE, Yersinia pestis, or the ability to produce EXOTOXINS, seen in Staphylococcus aureus.

These latter mutations, which involve addition, deletion, or substitution of single bases, are called _____ mutations.

These latter mutations, which involve addition, deletion, or substitution of single bases, are called POINT mutations.

These promoter sequences provide the signal for RNA polymerase to bind to the DNA. Then there is a special codon called the _____ codon, which is where the RNA polymerase begins its transcription.

These promoter sequences provide the signal for RNA polymerase to bind to the DNA. Then there is a special codon called the INITIATION codon, which is where the RNA polymerase begins its transcription.

This manner of synthesis produces one strand containing short fragments of DNA (100 to 1,000 bases long) called ______ fragments.

This manner of synthesis produces one strand containing short fragments of DNA (100 to 1,000 bases long) called Okazaki fragments.

The sequence of bases along the length of a gene constitutes the language of DNA. For this language to be preserved for hundreds of generations, it will be necessary for the genetic program to be duplicated and passed on to each offspring. This process of duplication is called _______.

This process of duplication is called DNA REPLICATION.

This property—of an amino acid being represented by several codons—is called _____ and allows for the insertion of correct amino acids (sometimes) even when mistakes occur in the DNA sequence, as they do with regularity.

This property—of an amino acid being represented by several codons—is called REDUNDANCY and allows for the insertion of correct amino acids (sometimes) even when mistakes occur in the DNA sequence, as they do with regularity.

This same phenomenon in eukaryotic cells, termed ______, is an essential aspect of genetically engineered yeasts, plants, and mice, and it has been proposed as a future technique for curing genetic diseases in humans.

This same phenomenon in EUKARYOTIC cells, termed TRANSFECTION, is an essential aspect of genetically engineered yeasts, plants, and mice, and it has been proposed as a future technique for curing genetic diseases in humans. (Equivalent of recombination)

Thus, in DNA, the purine adenine (A) always pairs with the pyrimidine _______, and the purine guanine (G) always pairs with the pyrimidine ______.

Thus, in DNA, the purine adenine (A) always pairs with the pyrimidine thymine (T), and the purine guanine (G) always pairs with the pyrimidine cytosine (C).

Making single-stranded DNA breaks to relieve supercoiling at origin

Topoisomerase I

Making double-stranded DNA breaks to remove supercoiling ahead of origin and separate replicated daughter DNA molecules

Topoisomerase II (DNA gyrase) and IV

Causes cross-links between adjacent pyrimidines

Ultraviolet

Ultraviolet repair mechanisms are successful only for a relatively small number of UV mutations. Cells cannot repair severe, widespread damage and will die. In humans, the genetic disease ______ is due to nonfunctioning genes for enzymes responsible for excising pyrimidine dimers caused by UV light. Persons suffering from this rare disorder (XP) develop severe skin cancers.

Ultraviolet repair mechanisms are successful only for a relatively small number of UV mutations. Cells cannot repair severe, widespread damage and will die. In humans, the genetic disease XERODERMA PIGMENTOSA is due to nonfunctioning genes for enzymes responsible for excising PYRIMIDINE DIMERS caused by UV light. Persons suffering from this rare disorder (XP) develop severe skin cancers.

When bacteria turn on or off a complement of genes that leads to obvious phenotypic changes, it is sometimes called _____

When bacteria turn on or off a complement of genes that leads to obvious phenotypic changes, it is sometimes called PHASE VARIATION

When the idea of their existence (TEs) in CORN plants was first proposed by geneticist Barbara _____ in 1951, it was greeted with nearly universal skepticism because it had long been believed that the location of a given gene was set and that genes did not or could not move around.

When the idea of their existence (TEs) in CORN plants was first proposed by geneticist Barbara MCCLINTOCK in 1951, it was greeted with nearly universal skepticism because it had long been believed that the location of a given gene was set and that genes did not or could not move around.

(Step 7>>) When this codon is reached, a special enzyme breaks the bond between the final _____ and the finished polypeptide chain, releasing it from the ribosome.

When this codon is reached, a special enzyme breaks the bond between the final tRNA and the finished polypeptide chain, releasing it from the ribosome.

With new findings in the area of gene expression, we now prefer to speak of a GENE as a segment of _____ that contains the necessary code to make a protein or an _____.

With new findings in the area of gene expression, we now prefer to speak of a gene as a segment of DNA that contains the necessary code to make a protein or an RNA.

The strand of new DNA that must be synthe- sized in short segments and later sealed together to form a strand in the 3′ to 5′ direction.

lagging strand

The strand of new DNA that is synthesized in a continuous manner in the 5′ to 3′ direction.

leading strand

Sequence of amino acids in protein and transports the DNA master code to the ribosome

mRNA

One problem with drugs that selectively disrupt bacterial ribosomes is that the mitochondria of humans contain a bacterial type of ribosome, and these drugs may inhibit the function of the host's _____.

mitochondria

A length of RNA that is inserted initially during replication before it is replaced by DNA.

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