OSU Biology 1113 Final Exam - Mackey

An accumulation of A and no production of B and C.

A --> B --> C A mutation results in a defective enzyme A. What would be a consequence of that mutation?

2

A --> B --> C According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

Minimal medium supplemented with nutrient B only.

A --> B --> C If A, B and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on what media?

Minimal medium supplemented with C only.

A --> B --> C If A, B and C are all required for growth, a strain that is mutant for the gene encoding enzyme B would be able to grow on what media?

Duplication

A DNA segment in a chromosome that is a copy of another segment.

Gene

A DNA sequence that is expressed to form a functional product: either RNA or polypeptide.

Translocation

A chromosome abnormality caused by the rearrangement of parts between nonhomologous chromosomes.

either an insertion or a deletion of a base

A frameshift mutation could result from __________.

Corepressor

A lack of which nonprotein molecule would result in the inability of the cell to "turn off" genes?

Proteins in the cell will include lysine insteas of phenylalanine at amino acid positions specified by the codon UUU.

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of phenylalanine. The consequence of this for the cell will be what?

Promoter

A mutation in which section of DNA could influence the binding of RNA polymerase?

Exon

A mutation is which part of the gene is likely to be most damaging to a cell?

Continuous transcription of the structural gene controlled by that regulator.

A mutation that inactivates the regulatory gene of a repressible operon in an E.coli cell would result in what?

DNA polymerase can only add nucleotides to the free 3' end.

A new DNA strand elongates only in the 5' to 3' direction because ____________.

Any mutation in the sequence is selected against.

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. What might this illustrate?

UUU

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is ________.

3' UCA 5'

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _________.

Increased chromatin concentration.

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. What results would she likely see?

Decreased chromatin concentration.

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments using this procedure in flies, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. What results would she likely see?

Codon

A series of 3 nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

many noncoding stretches of nucleotides are present in mRNA

A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that ________.

~4.4 thousand

A typical bacterial chromosome has ~4.6 million nucleotides. How many genes does this support?

1000 X

About how many more genes are there in the haploid human genome than in a typical bacterial genome?

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _______________.

Decendents of the living cells are also phosphorescnt.

After mixing a heat-killed phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to flouresce is a heritable trait?

Allolactose binds to the repressor protein.

Allolactose induces the synthesis of the enzyme lactase. An E.coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. What occurs when the lactose enters the cell?

Allowing the organism to adjust to changes in environmental conditions.

Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in what way?

5' RNA nucleotides, DNA Nucleotides 3'

An Okazaki fragment has which of the following arrangements?

A+C = G+T

An analysis of the nucleotide composition of DNA will reveal what?

The amino acid methionine will not bind.

An experiment has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. What is a likely result?

Histones

Any group of basic proteins found in chromatin.

1.5%

Approximately what proportion of the DNA in the human genome codes for proteins or functional RNA?

The tRNA that was in the A site moves to the P site.

As a ribosome translocates along an mRNA molecule by one codon, what occurs?

5' ACGUUAGG 3'

At a specific area of a chromosome, the sequence of nuckeotides below is present where the chain opens to form a replication fork: 3' CCTAGGCtGCAATCC5' An RNA primer is formed starting at t of the template. What represents the primer sequence?

The amount of A is always equivalent to T and C to G.

Chargaff's analysis of the relative base composition of DNA was significant because he was able to show ___________________.

12%

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

Transcription

Differentiation is mostly controlled at what level?

RNA

During splicing, which molecular component of the spliceosome catalyzes the excision reaction?

P,A

During translation, ___ site within the ribosome holds the growing amino acid chain while the ____ site holes the next amino acid to be added to the chain.

The untranslated regions at either end of the coding sequence.

Each eukaryotic mRNA, even after post-transcriptional modification, includes 5' and 3' UTRs. What are these?

Histone acetylation of nucleosomes.

Eukaryotic cells can control hene expression with what mechanism?

Gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach.

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

RNA polymerase must bind to the promoter and the repressor must be inactive.

For a repressible operon to be transcribed, what must occur?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because _____________.

bacteria and eukaryotes

Gene expression in Archaea differs from that in other prokaryotes. It shares features with _________.

euchromatin

Heterochromatin is highly condensed whereas _____________ is less compact.

the formation of higher-level chromatin structures

Histone H1 is not present in the nucleosome bead; instead it is involved in _________________.

Measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

How can you tell whether a gene's expression s controlled at a level of transcription of translocation?

THETACATETHERAT

How do you represent a frameshift mutation in the sentence THECATATETHERAT?

THECATARETHERAT

How do you represent a single substitution mutation in the sentence THECATATETHERAT?

It stimulates the binding of RNA polymerase to the promoter.

How does active CAP induce expression of the genes of the lactose operon?

When RNA polymerase binds to a sigma to create a holoenzyme and the sigma guides the RNA polymerase to certain locations where transcription should begin

How does transcription begin?

The cell's DNA couldn't be packed into its nucleus.

If a cell were unable to produce histone proteins, what would be a likely effect?

Increased concentrations of sugars such as arabinose in the cell.

If glucose is available in the environment of E.coli, the cell responds with very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect would be a measurable effect?

2

If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system of four different nucleotides?

have turned off or slowed down the process of transcription

If you were to observe the activity of methylated DNA, you would expect it to ___________.

No replication fork will be formed.

In E.coli, there is a mutation gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

The 30nm chromatin fiber.

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

Centromeres will be euchromatic rather than heterochromatic and the cells will soon die in culture.

In a series of experiments the enzyme Dicer has been inactivated in cells from various vertebrates, and the centromere is abnormally formed from chromatin. What is most likely to occur?

The molecule is digested my exonucleases since it is no longer protected at the 5' end.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly (A) tail. What would you expect him to find?

transcription.

In both eukaryotes and prokaryotes, gene expression is primarily regulated at the level of _________.

both euchromatin and histone acetylation

In eukaryotes, transcription is generally associated with ____________.

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

In his transformation experiments, what did Griffith observe?

Chromosome breakage and rejoining.

In order for chromosomes to undergo inversion or translocation, what is required?

Histone tail phosphorylation prohibits chromosome condensation.

In prophase I of meiosis in female Drosophila, studies have shown that there is phosphorylation of an amino acid in the tails of histones. A mutation in flies that interferes with this process results in sterility. What can be concluded from this?

Alter the lever of production of various enzymes.

In response to chemical signals, prokaryotes can do what?

The various domains of the polypeptide product.

In structural organization of many eukaryotic genes, individual exons may be related to what?

DNA contains phosphorus, but protein does not.

In trying to etermine whether DNA or protein is genetic material, Hershey and Chase made use of what fact?

RNA polymerase can initiate RNA synthesis but DNA polymerase requires a primer to initiate DNA synthesis.

In what action does RNA polymerase differ from DNA polymerase?

They cannot repair thymine dimers.

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, This occurs because their cells have which impaired ability?

Their presence allows exons to be shuffled.

Introns are significant to biological evolution because ______________.

A sequence of bases.

It became apparent to Watson and Crick after the completion of their model that the DNA molecule could carry a vast amount of hereditary information in what?

The particulate nature of the hereditary material.

Mendel and Morgan did not know about the structure of DNA; however, which of the following of their contributions was necessary to Watson and Crick?

DNA replication.

Methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication during what?

having different genes expressed.

Muscle cells and nerve cells in one species of animal owe their differences in structure to _________________.

Replication is not conservative.

Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident about what conclusion?

Excision of introns

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes ____________.

Translocation.

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is the alteration called?

1. Griffith 2. Avery, McCarty and MacLeod 3. Hershey and Chase 4. Watson and Crick 5. Meselson and Stahl

Place the scientists' names in correct chronological order, starting with the first scientist to make a contribution to understanding the structure and function of DNA.

Replication without separation.

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?

1. A small ribosomal subunit binds with mRNA 2. An aminoacyl-tRNA binds to the A site 3. A peptide bond forms between the new amino acid and a polypeptide chain 4. tRNA translocates to the P site 5. tRNA leaves the P site and the P site remains vacant.

Put the events of protein synthesis in the proper sequence.

It might allow the polymerase to recognize different promoters under certain environmental conditions.

RNA polymerase in prokaryotes is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. What is the most probable advantage for the organism of such sigma switching?

3' to 5' along the template strand

RNA polymerase moves in which direction along the DNA?

prokaryotic chromosomes have a single origin of replication whereas eukaryotic chromosomes have many

Replication in prokaryotes differs from replication in eukaryotes because ________________.

Okazaki fragments.

Short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. They are complementary to he lagging template strand, together forming short, double stranded DNA sections.

Point

Sickle-cell disease is probably a result of what kind of mutation?

binding to intracellular receptors and promoting transcription of specific genes

Steroid hormones produce their effects in cells by ____________.

The two types of tetramers associate to form an octamer.

Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules 2H2B molecules and and the other as 2 H3 and 2 H4 molecules. What is supported by this data?

The structural genes will be transcribed continuously.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon (past the transacetylase), what would likely occur when the cell is exposed to lactose?

Beta galictosidase will be produced.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase gene and the permease gene, what would likely happen?

The lac operon will function normally.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the repressor gene (lac I), along with its promoter to a position at some several thousand base pairs away from its normal position, what would you expect to occur?

DNA in both daughter cells would be radioactive.

Suppose you are provided with an actively dividing culture of E.coli to bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only.

The "universal" genetic code is now known to have exceptions. Evidence for this could be found if what is true?

The the critical function of telomeres must be maintained.

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?

the number of hydrogen bonds between A and T in DNA

The TATA sequence is found only several nucleotides away from the start site of transcription. This is probably because of ________________.

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that ______________________.

8

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adesonine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?

Adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn.

The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?

differentiated cells retain all the genes of the zygote

The fact that plants can be cloned from somatic cells demonstrates that _________________.

DNA was the first genetic material.

The genetic code is essentially the same for all organisms. From this, one can assume the following: - a gene from an organism could theoretically be expressed by any other organism. - all organisms have a common ancestor - the same codons in different organisms usually translate into the same amino acids - different organisms have the same number of different types of amino acids On can not assume that _________________.

The cyclic AMP and lactose levels are both high within the cell.

The lactose operon is likely to be transcribed when _________.

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized the opposite direction.

The leading and the lagging strands differ in that ___________________________.

ATP, RNA and DNA

The nitrogenous base adenine is found in all members of which group?

Translation

The process by which a sequence of nucleotide triplets in a messenger RNA molecule gives rise to a specific sequence of amino acids during synthesis of a polypeptide or protein.

Transcription

The process by which genetic information, represented by a sequence of DNA nucleotides is copied into newly synthesized molecules of RNA with the DNA serving as a template.

differential gene expression

The process of cellular differentiation is a direct result of _____________.

polypeptide factors plus GTP

The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits and _____________.

RNA polymerase

The transcribing enzyme is...

Exit tunnel.

The transfer of RNA 1 attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA 2 in the ribosome already. Where does tRNA 2 move to after this bonding of lysine to the polypeptide?

Newly formed polypeptide.

The transfer of RNA 1 attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA 2 in the ribosome already. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?

Peptidyl transferase.

The transfer of RNA 1 attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA 2 in the ribosome already. Which enzyme causes a covalent bond to attach lysine to the polypeptide?

is turned off whenever tryptophan is added to the growth medium.

The tryptophan operon is a repressible operon that __________________.

The rules for base pairing between the third base of a codon and tRNA are flexible.

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that ____________.

1. endonuclease 2. DNA polymerase I 3. DNA ligase

To repair a thymine dimmer by neucleotide excision repair, in which order do the necessary enzymes act?

Other transcription factors

Transcription factors in eukaryotes usually have DNA binding domains as well as other domains also specific for binding. In general what would you expect many of them to be able to bind to?

Several transcription factors (TFs)

Transcription in eukaryotes involves what in addition to RNA polymerase?

3' to 5'; 5' to 3'

Transcription occurs along a _____ template forming mRNA in a _____ direction

starts when the pathway's substrate is present

Transcription of the structural genes in an inducible operon _______________.

RNA acts an an expendable copy of the genetic material

Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because ________.

non protein coding DNA that is transcribed into several kinds of small RNAs with biological function.

What accounts for most of the DNA that is not protein-coding sequences?

Exons

What are the coding segments of a stretch of eukaryotic DNA called?

DNA methylation and histone acetylation.

What are two potential devices that eukaryotic cells use to regulate transcription?

A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate.

What best describes the addition of nucleotides to a growing DNA chain?

Activator

What binds to the site in the DNA far from the promoter to stimulate transcription?

Alternative RNA splicing.

What can allow the production of proteins of different sizes from a single mRNA?

The diameter of the helix.

What can be determined directly from X-ray diffraction photographs of crystallized DNA?

Inducer

What can be taken up by the cell and cause the binding of the repressor so that the repressor no longer binds to the operator?

Repressor.

What can inhibit transcription by blocking the binding of positively acting transcription factors to the DNA?

A poly (A) signal sequence.

What codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~ 10-35 nucleotides away?

The eukaryotic chromosome.

What consists of a single linear molecule of double-stranded DNA?

Ligase.

What covalently connects segments of DNA?

The nucleotide sequence of the template strand.

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

Their products are transcription factors

What do gap genes, pair-rule genes, segment polarity genes and homeotic genes all have in common?

The coordinated control of gene expression in bacteria.

What does the operon model attempt to explain?

Assimilation of external DNA into a cell.

What does transformation involve in bacteria?

Reverse Transcriptase

What enzyme is necessary to convert an RNA sequence back to its complememntary DNA sequence?

Dicer

What enzyme trims small double-stranded RNAs into molecules that can block translation?

Single-strand binding proteins.

What helps to hold the DNA strands apart while they are being replicated?

5' cap and poly (A) tail

What helps to stabilize mRNA by inhibiting its degradation?

To translocate polypeptides across the ER membrane.

What is a function of a single peptide?

Polyribosome

What is a group of ribosomes reading a single mRNA simultaneously?

Targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease.

What is a research scenario that would benefit from the recent discoveries regarding RNAs?

siRNA

What is a short, double-stranded RNA, on of whose strands can complement and inactivate a sequence of mRNA.

Ribozyme

What is an RNA with enzymatic activity?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

A cyclin that usually acts in G1 now that the cell in in G2

What is most likely to have a small protein called ubiquitin attached to it?

The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA.

What is one of the first events in translation in eukaryotes?

It Introduces a premature stop codon into the mRNA.

What is the effect of a nonsense mutation in a gene?

To add nucleotides to the end of a growing DNA strand.

What is the function of DNA polymerase III?

Relieving he strain in the DNA ahead of the replication fork.

What is the function of topoisomerase?

rRNA

What is the most abundant type of RNA?

RNA interference

What is the phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA?

Join Okazaki fragments together.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Bind to the repressor protein and activate it.

What is the role of a metabolite that controls a repressible operon?

Terminator

What is the site in the DNA, located near the end of the final exon, encoding an RNA sequence that determines the 3' end of the transcript?

Translation can begin while transcription is still in progress.

What is true about protein synthesis in prokaryotes?

snRNPs

What joins together to form a large structure called the spliceosome?

Hydrogen.

What kind of chemical bond is found between paired bases of the DNA double helix?

double-stranded DNA, 4 kinds of dNTPs, primers and origins.

What materials are required by both eukaryotes and prokaryotes for replication?

Removal of the 5' cap

What procedure is most likely to hasten mRNA degradation in a eukaryotic cell?

Repressor

What protein is produced by a regulatory gene?

DNA polymerase I

What removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

Helicase.

What separates the DNA strands during replication?

TAC

What sequence on the template strand corresponds to the first amino acid inserted into a protein?

Primase.

What synthesizes short segments of RNA?

RNA polymerase II

What type of RNA polymerase is involved in transcription of mRNA for a globin protein?

Hydrogen bonding between base pairs.

What type of bonding is responsible for maintaining the shape of the tRNA molecule?

A deletion of 2 nucleotides.

What type of mutation, resulting in an error in the mRNA just after the AUG start of translation is likely to have the most serious effect on the polypeptide product?

Reduction in chromosome length.

What would you expect of a eukaryotic cell lacking telomerase?

General transcription factors.

What, in eukaryotes, binds to other proteins or to a sequence element within the promoter called the TATA box?

Methylation and phosphorylation of histone tails.

When DNa is compacted by histones into 10nm and 30nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin mus constantly alter its structure. Which processes contribute to this dynamic activity?

The viral proteins will be radioactive.

When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result?

its 3D shape.

When a tRNA molecule is shown twisted into an L shape, the form representd is _________.

As soon as transcription has begun.

When does translation begin in prokaryotic cells?

An assembled ribosome with a polypeptide attached to the tRNA in the P site.

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, what would you be able to isolate?

a signal-recognition particle that brings ribosomes to a receptor in the ER membrane.

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by _________________.

Base-pair deletion.

Which DNA mutation is most likely to be damaging to the protein it specifies?

DNA polymerase III

Which enzyme catalyzes the elongation of a DNA strand in the 5' --> 3' direction?

Organization of the genes into clusters, with local chromatin structures influencing the expression of all the genes at once.

Which mechanism(s) are used to coordinately control the expression of multiple, related genes in eukaryotic cells?

DNA to protein

Which mode of information transfer doesn't occur?

mRNA

Which molecule contains the genetic code?

RNA polymerase binds to the promoter region to begin transcription.

Which of the following is true for both prokaryotic and eukaryotic gene expression?

A triplet in the same reading frame as an upstream AUG.

Which of the following nucleotide triplets represents a codon?

nucleosome. 30nm chromatin fiber, looped domain

Which of the following represents the order of increasingly higher levels of organization of chromatin?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off he DNA and release the transcript.

Which of the following statements best describes the termination of transcriptions in prokaryotes?

A base deletion near the start of a gene.

Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?

Oswald Avery, Maclyn McCarty and Colin MacLeod.

Which scientist was responsible for the following discovery: Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA.

Edwin Chargaff.

Which scientist was responsible for the following discovery: In DNA from any species, the amount of adenine equals the amount of thymine and the amount of guanine equals the amount of cytosine.

Alfred Hershey and Martha Chase.

Which scientist was responsible for the following discovery: Phage DNA with labeled proteins or DNA was allowed to infect bacteria. It was shown that the DNA, but not the protein, entered the bacterial cells and was therefore concluded to be the genetic material.

Eukaryotic exons may be spliced in alternative patterns.

Why can gene expression be altered at the level of post-transcriptional processing in eukaryotes but not prokaryotes?

Histones are positively charged and DNA is negatively charged.

Why do histones bing tightly to DNA?

Purines pair with pyrimidines.

Why does the DNA double helix have a uniform diameter?

It involves frameshift mutations and inversions.

Why is differentiation of cells not easily reversible?

It might substitute an amino acid in the active site.

Why might a point mutation in DNA make a difference in the level of protein's activity?

Leading strands of Okazaki fragments.

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or millions of nucleotides long) and the other includes short stretches of DNA (several hundred nucleotides). These two classes of DNA probably represent____________________.

The amino acid will bind covalently.

if the 3' end of the tRNA is projecting beyond the 5' end what will occur at the 3' end?