Bio 1107

`An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

What is the function of the release factor in translation?

It binds to the stop codon in the A site in place of a tRNA.

What happens to the cut-out intron after alternative RNA splicing?

It is rapidly degraded.

What must happen to a newly made polypeptide before it can be secreted from a cell?

Its signal sequence must target it to the ER, after which it goes to the Golgi.

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. Which of the following statements best explains this fact?

Many noncoding stretches of nucleotides are present in eukaryotic DNA

Some photosynthetic bacteria (e.g., purple sulfur bacteria) have only photosystem I, whereas others (e.g., cyanobacteria) have both photosystem I and photosystem II. No photosynthetic bacteria have only photosystem II. Which of the following might be a possible explanation for this observation?

Photosynthesis with only photosystem I is more ancestral.

PS II (gets electrons from splitting of water)

Purpose · Splits H2O · Sends electrons through electron transport chain · Releases oxygen Special Pair P680

Where do the enzymatic reactions of the Calvin cycle take place?

Stroma of the chloroplast

anchorage dependence

The requirement that a cell must be attached to a substratum in order to initiate cell division.

Which of the following mechanisms removes nucleotides that are paired incorrectly during DNA replication?

mismatch repair A: C

What is the Calvin Cycle?

process in where ATP and NADPH from the light- independent reactions to produe- high energy sugars.

The process of translation in both prokaryotes and eukaryotes requires tRNAs, amino acids, and ribosomal subunits. Which of the following components must also be present for translation to proceed?

protein factors and GTP

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

Which of the following reactions produces the oxygen released by photosynthesis?

splitting of water molecule

cohesin

the protein responsible for binding sister chromatids during the early stage of anaphase

A cell in G2 of the cell division cycle contains 20 chromatids. How many centromeres are present in this cell?

20

In which direction does RNA polymerase move along the DNA?

3' to 5' along the template strand

Given the locally unwound double strand of DNA in the figure above, in which direction and on what strand does the RNA polymerase move during transcription?

3' → 5' along the template strand

Examine the table of codons in the figure above. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3'-AAA-GAA-TAA-CAA-5'.

Use the following model of a eukaryotic transcript to answer the question. E1-4 refer to the exons, and I1-3 refer to the introns in the pre-mRNA transcript. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'

5' UTR E1 E2 E3 E4 UTR 3'

Examine the table of codons in the figure above. A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide?

5'-TTT-CCC-AAA-GGG-TTT-CCC

The genetic code is essentially the same for all organisms. Based on this information, one can logically assume which of the following statements to be correct?

A gene from an organism can theoretically be expressed by any other organism.

Which of the following processes only occurs in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA, and a cap is added to the 5' end.

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

A) 8% A : A

Which of the following statements correctly describes how the leading and the lagging strands of DNA formed during DNA replication differ?

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

During DNA replication, which of the following enzymes separates the DNA strands during replication?

A) helicase

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 even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

A) leading strands and Okazaki fragments. A: A

Where does the Calvin cycle take place?

A) stroma of the chloroplast

Which of the following characteristics of the structure of DNA allows it to carry a large amount of hereditary information ?

A) the sequence of bases

What are the products of linear electron flow?

ATP and NADPH

The nitrogenous base adenine is found in all members of which of the following groups of molecules?

ATP, RNA, and DNA

What evidence exists that the evolution of photosynthesis and cellular respiration support the concept that there is a common ancestry for all organisms?

All organisms perform cellular respiration, using oxygen and glucose, which are produced by photosynthesis.

What is a ribozyme?

An RNA with enzymatic activity

Examine the simple metabolic pathway in the figure above. A mutation results in a defective enzyme 1. Which of the following results would be a consequence of that mutation?

An accumulation of A and no production of B and C

Which of the following molecules are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

Atp and NADPH

If ATP used by this plant is labeled with radioactive phosphorus, which molecule or molecules of the Calvin cycle will be radioactively labeled first?

B and D only

Somatic cells in elephants have 56 chromosomes. How many chromosomes would be carried by the gametes produced by elephants?

B) 28

What is meant by the description "antiparallel" regarding the two strands of nucleic acids that make up DNA?

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

Following DNA replication, each eukaryotic chromosome consists of two identical DNA molecules known as?

B) sister chromatids A: B

In photosynthetic cells, which reactions is (are) responsible for the synthesis of ATP by chemiosmosis?

Both photosynthesis and cellular respiration

Which of the following metabolic pathways produce(s) reduced soluble electron carriers?

Both the light reactions of photosynthesis and the citric acid cycle

How do small RNAs in the spliceosome initiate the splicing of the pre-mRNA?

By base pairing to specific sites along the intron

In an analysis of the nucleotide composition of DNA, which of the following will be found in a given DNA molecule?

C) A + C = G + T

Which enzyme in E. coli catalyzes the elongation of a DNA strand in the 5' → 3' direction?

C) DNA polymerase III

Which of the following statements correctly describes one characteristic of DNA replication in eukaryotes?

C) In the lagging strand, DNA is replicated in short pieces called Okazaki fragments, which are then joined together at the end of the process.

Humans produce skin cells by mitosis and gametes by meiosis. Which of the following statements about the nuclei of skin cells is correct?

C) They contain twice as much DNA as the nuclei of gametes produced by meiosis.

During DNA replication, which of the following enzymes covalently connects segments of DNA?

C) ligase

What is the function of DNA polymerase III in replication in E. coli?

C) to add nucleotides to the 3' end of a growing DNA strand

Beginning with a fertilized egg (zygote), how many cells would be present in an embryo following a series of five cell divisions?

D) 32

Which of the following components make(s) up eukaryotic chromatin?

D) DNA and proteins

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

D) DNA in both daughter cells would be radioactive. Answer: D

After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?

D) Descendants of the living cells are also phosphorescent. Answer: D

Which of the following statements correctly describes one of Chargaff's rules regarding DNA?

D) The percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the DNA of a given species. Answer: D

1) Which of the following statements most accurately describes transformation in bacteria?

D) Transformation is the assimilation of external DNA into a cell. Answer: D

During DNA replication in E. coli, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

DNA polymerase I A: D

Why does a new DNA strand elongate only in the 5' to 3' direction in replication?

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

Which of the following statements correctly describes a reaction associated with photosystem II

Electrons released from the P680 chlorophyll are replaced by electrons derived from water.

Chemiosmosis in chloroplasts involves which of the following processes?

Establishment of a proton gradient across the thylakoid membrane

In mitochondria, the electron transport chain pumps protons from the matrix into the intermembrane space. In what direction are protons pumped by the electron transport chain in chloroplasts?

From the stroma to the thylakoid space

Which of the following statements describes one of the functions of GTP in translation?

GTP provides the energy for the formation of the initiation complex, using initiation factors.

Which of the following statements correctly defines the process of gene expression?

Gene expression is the process by which DNA directs the synthesis of proteins.

Where are electron transport chains that are responsible for ATP production located in plant cells?

In the thylakoid and inner mitochondrial membranes

Process: Light reactions (occurs in thylakoid)

Input 1. Light 2. Water 3. NADP+ 4. ADP Outputs 1. 1 G3P (makes glucose: takes 6 turns of the cycle to produce one molecule of glucose) 2. 9 ADP 3. 6 NADP+

Calvin cycle (occurs in stroma)

Input: 1. ATP 2. NADPH 3. CO2 Output 1. 1 G3P (makes glucose: takes 6 turns of the cycle to produce one molecule of glucose) 2. 9 ADP 3. 6 NADP

Which of the following is a function of a poly-A tail in mRNA?

It helps protect the mRNA from degradation by hydrolytic enzymes.

Which of the following statements best describes the function of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor

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

It joins Okazaki fragments together. A: C

P680+ is often considered the strongest biological oxidizing agent. Given its function, why is this necessary?

It obtains electrons from the oxygen atom in a water molecule, so it must have a greater affinity for electrons than oxygen has.

Which of the following statements correctly describes an activity directly associated with photosystem I?

It receives electrons from the electron transport chain associated with thylakoid membranes.

Which of the following events occurs in the light reactions of photosynthesis?

Light is absorbed and transferred to reaction center chlorophyll

As temperatures increase, gases such as CO2 diffuse faster. As a result, plant leaves will lose CO2 at a faster rate than normal. If the amount of light impacting on the leaf and the amount of water available is adequate, predict how this loss of gas will affect photosynthesis in the leaf.

Loss of gases, mainly CO2, will affect photosynthesis in the leaf, as the Calvin cycle will slow down and possibly stop because of inadequate carbon to fix in the system.

What compound provides the reducing power for the Calvin cycle reactions?

NADPH

What is the overall outcome of the light reactions in photosynthesis?

NADPH and ATP molecules are produced during the light reactions and are used to power the light independent reactions.

Photorespiration occurs when rubisco combines RuBP with which of the following molecules?

O2

During the process of alternative RNA splicing, where on a pre-mRNA transcript does a spliceosome bind?

On certain sequences of an intron

Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying the amino acid leucine, Leu). What will be the effect on the translation of polypeptides in this cell?

One altered tRNA molecule will have little effect because it will compete with many "normal" ones.

What are the phases of Meiosis

Prophase 1, Metaphase 1, Anaphase 1, Telophase 1 End result: Sister chromosome separate during anaphase II gives you 4 haploid daughter cells

PS I (gets electrons from electron transport chain)

Purpose Makes NADPH · Generates ATP Special Pair P700

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA known as pre-mRNA?

RNA polymerase II

The NADPH required for the Calvin cycle is produced by which of the following metabolic reactions?

Reactions initiated in photosystem I

Use the following model of a eukaryotic transcript to answer the question. E1-4 refer to the exons, and I1-3 refer to the introns in the pre-mRNA transcript. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might be the result of this removal?

Removal of the 5' UTR also removes the 5' cap, so the mRNA may be quickly degraded by hydrolytic enzymes.

Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet they are able to survive. Which of the following experimental approaches would be a reasonable way to detect the lack of photosystem II in these organisms?

Test whether they release O2 in the light

Imagine that a researcher has developed a way to isolate thylakoids from chloroplasts and to make the pH of the thylakoid space acidic. If these isolated thylakoids are transferred to a pH8 solution in the dark, what might the researcher expect to observe?

That the isolated thylakoids produce ATP

Which of the following metabolic processes consume(s) CO2?

The Calvin cycle only

cleavage furrow

The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate.

Carbon, in the form of CO2, must be taken from the atmosphere and attached to an existing organic molecule in the Calvin cycle. Therefore, the carbon is bound to the molecule. The products of the cycle only occur because of the added carbon. What are the products of the Calvin cycle and what is regenerated?

The product of the Calvin cycle is glyceraldehyde-3 phosphate and RuBP is regenerated.

Which of the following statements is true about the Krebs cycle and the Calvin cycle?

They both require a net input of ATP

Where is the electron transport chain associated with photophosphorylation located in plant cells?

Thylakoid membranes of chloroplasts

Where are ATP synthase complexes located in a plant cell?

Thylakoid membranes only

Why does it take three turns of the Calvin cycle to produce G3P, the initial product of photosynthesis?

To fix enough carbon to export one G3P molecule.

What is the primary function of the Calvin cycle?

To produce simple sugars from carbon dioxide

5' cap

a modified form of guanine nucleotide added onto the end of a pre-mRNA molecule.

Which of the following would you expect of a eukaryote lacking telomerase?

a reduction in chromosome length in gametes A:D

centrosome

a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles

Why are carnivores, such as lions, dependent on photosynthesis to survive?

because the prey of lions are generally herbivores which depend on autotrophs

) Accuracy in the translation of mRNA into the sequence of amino acids in a polypeptide depends on specificity in which of the following characteristics?

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

Generation of proton gradients across membranes occurs during which of the following reactions?

both photosynthesis and cellular respiration

Which of the following reactions reduce(s) oxygen to form water

both the light reactions of photosynthesis and the Calvin cycle

In chemiosmosis in mitochondria, protons flow from the intermembrane space into the matrix. In what direction do protons flow during chemiosmosis in chloroplasts?

from the thylakoid space to into the stroma

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following statements is true?

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

centromere

in a duplicated chromosome, the region on each sister chromatid where it is most closely attached to its sister chromatid by proteins that bind to the centromeric DNA. Other proteins condense the chromatin in that region, so it appears as a narrow "waist" on the duplicated chromosome.

What are the phases of Mitosis

interphase, prophase, metaphase, anaphase, telophase End result: Two diploid daughter cells

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5'-CCG-ACG-3' (mRNA). The charged transfer RNA molecules shown in the figure below (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. The dipeptide that will form will be

proline-threonine

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

several transcription factors

Which of the following molecule(s) help(s) to hold the DNA strands apart while they are being replicated?

single-strand binding proteins

chromatin

the complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

density-dependent inhibition

the phenomenon observed in normal animal cells that causes them to stop dividing when they come in contact with one another.

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

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

Which of the following events in translation is the first to occur in eukaryotes?

the small subunit of the ribosome recognizing and attaching to the 5' cap of mRNA

What is the primary function of the pigment molecules in a light-harvesting complex?

to transfer light energy to the reaction-center chlorophyl