OSU Biology 1113 Final Exam - Mackey

Duplication

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

Translocation

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

Translocation.

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

Chromosome breakage and rejoining.

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

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?

Assimilation of external DNA into a cell.

What does transformation involve in bacteria?

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.

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?

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?

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?

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.

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.

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.

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?

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?

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 ___________________.

The diameter of the helix.

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

Purines pair with pyrimidines.

Why does the DNA double helix have a uniform diameter?

Hydrogen.

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

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?

A+C = G+T

An analysis of the nucleotide composition of DNA will reveal 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?

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

Replication in prokaryotes differs from replication in eukaryotes because ________________.

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?

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?

Replication is not conservative.

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

5' RNA nucleotides, DNA Nucleotides 3'

An Okazaki fragment has which of the following arrangements?

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?

DNA polymerase III

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

The nucleotide sequence of the template strand.

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

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?

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?

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?

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?

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. 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?

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

What is the function of DNA polymerase III?

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____________________.

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.

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?

Ligase.

What covalently connects segments of DNA?

Primase.

What synthesizes short segments of RNA?

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 ______________________.

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 ___________________________.

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?

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

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

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

What is the function of topoisomerase?

Join Okazaki fragments together.

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

Single-strand binding proteins.

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

They cannot repair thymine dimers.

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

Reduction in chromosome length.

What would you expect of a eukaryotic cell lacking telomerase?

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

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

~4.4 thousand

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

Histones

Any group of basic proteins found in chromatin.

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?

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?

1000 X

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

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?

The 30nm chromatin fiber.

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

The eukaryotic chromosome.

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

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?

the formation of higher-level chromatin structures

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

Histones are positively charged and DNA is negatively charged.

Why do histones bing tightly to DNA?

nucleosome. 30nm chromatin fiber, looped domain

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

euchromatin

Heterochromatin is highly condensed whereas _____________ is less compact.

Codon

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

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 _____________.

2

A --> B --> C

According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

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?

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?

ATP, RNA and DNA

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

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 ________.

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?

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?

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 _________.

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 _________________.

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?

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

Which of the following nucleotide triplets represents a codon?

RNA polymerase binds to the promoter region to begin transcription.

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

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?

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?

3' to 5' along the template strand

RNA polymerase moves in which direction along the DNA?

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?

A poly (A) signal sequence.

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

RNA polymerase II

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

Several transcription factors (TFs)

Transcription in eukaryotes involves what in addition to RNA polymerase?

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?

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 ________________.

5' cap and poly (A) tail

What helps to stabilize mRNA by inhibiting its degradation?

Ribozyme

What is an RNA with enzymatic activity?

Exons

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

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 ________.

Excision of introns

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

Their presence allows exons to be shuffled.

Introns are significant to biological evolution because ______________.

Exon

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

snRNPs

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

RNA

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

Alternative RNA splicing.

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