Exam 3

B

In animals, where are most components of extracellular material synthesized? A. Smooth ER B. In the rough ER C. In the extracellular layer itself D. In the plasma membrane

B

In multicellular organisms, nondividing cells stay in Go phase. For the cell why is it better to be held in G1 rather than S, G2, or M Phase? A. G1 cells are larger and more likely to preform the normal functions of the cell B. G1 cells have not replicated their DNA in preparation for division. C. G1 cells are the only ones that do not have their chromatin in a highly condensed state D. MPF is required to enter S-phase, so the cell is committed to entering M-phase if the cycle moves beyond G1.

D

In studies of how traits are inherited, what makes certain species candidates for model organisms? A. They are the first organisms to be used in a particular type of experiment, so they are a historical "model" of what researchers expect to find. B. they are easy to study because a great deal is already know about them. C. they are the best or most fir of their type. D. They are easy to maintain, have a short life cycle, produce many offspring, and yield data that are relevant to many other organisms.

B

In the roundworm Ascaris, eggs and sperm have two chromosomes, but all other cells have four. Observations such as this inspired which important hypothesis? A. Before gamete formation, a special type of cell division leads to a quartering of chromosome number. B. Before gamete formation, a special type of cell division leads to halving of chromosome number C. After gamete formation, half the chromosomes are destroyed D. After gamete formation, either the maternal or the paternal set of chromosomes disintegrates.

A

In tigers, a recessive allele causes a white tiger. If one phenotypically normal tiger that is heterozyous is mated to another that is phenotypically white, what percentage of their offspring is expected to be white? A. 50% B. 75% C. 0% D. 100% E. 25%

A

A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino was crossed with a second black animal, 6 blacks and 6 albinos were obtained. What is the best explanation for this genetic situation. A. Albino is recessive; black is dominant B. Albino is dominant; black is incompletely dominant C. Albino and black are codominant D. Albino is recessive; black is codominant

D

A gap junction is a channel that connects adjacent cells. From substances listed, which one cannot pass through a gap junction? A. Ions that can regulate heartbeat B. Amino acids C. Nucleotides D. Ribosomes

D

A man and woman are both of normal pigmentation, but both have one parent who is albino. Albinism is an autosomal recessive trait. What is the probability that their first child will be albino? A. 0 B. 1/8 C. 1/2 D. 1/4 E. 1

A

A man who carries an allele of an X-linked gene will pass it on to? A. All of his daughters B. Half of his daughters C. All of his sons D. Half of his sons E. All of his children

A

A particular cell spends 4 hours in G1 phase, 2 hours in S phase, 2 hours in G2 phase, and 30 minutes in M phase. If a pulse-chase assay were preformed with radioactive thymidine on an asynchronous culture, what percentage of mitotic cells would be radiolabeled after 9 hours? A. 0% B. 50% C. 75% D. 100%

A

A recessive Allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color blind male. What is the probability that this couples first son will be color blind? A. 25% B. 50% C. About 66% D. 75% E. About 33%

D

After the S-phase, what comprises a single chromosome? A. two daughter chromosomes B. A double stranded DNA molecule C. Two single-stranded molecules of DNA D. two sister chromatids

Telomerase

An enzyme that uses an internal RNA template to synthesize DNA is?

D

Asbestos is a material that was once used extensively in construction. One risk from working in a building that contains asbestos is the development of asbestosis caused by the inhalation of asbestos fibers. Cells will phagocytize asbestos, but are not able to degrade it. As a result, asbestos fibers accumulate in . A. Mitochondria B. Ribosomes C. Peroxisomes D. Lysosomes

D

DNAs primary structure is made up of just four different bases, and its secondary structure is regular and highly stable. How can a molecule with these characteristics hold all the information required to build and maintain a cell? A. The information is first transcribed, then translated B. The messenger RNA produced from DNA has much more complex secondary structures, allowing mRNA to hold much more information. C. A protein coded for in DNA has much more complex primary and secondary structures, allowing it to hold much more information D. The information in DNA is in a code form that is based on the sequence of bases.

B

Dogs have 78 chromosomes in their diploid cells. If a diploid dog cell enters meiosis, how many chromosomes and chromatids will be present in each daughter cell at the end of meiosis 1? A. 39 Chromosomes and 39 Chromatids B. 39 Chromosomes and 78 Chromatids C. 78 Chromosomes and 78 Chromatids D. 78 Chromosomes and 156 Chromatids

B

Eukaryotic cells manufacture cytoskeletal proteins that help to maintain the cells' shape and functions. What would you predict about these proteins? A. They would initially contain signal sequences that would allow their entrance into the endoplasmic reticulum B. They would be manufactured on free ribosomes in the cytoplasm C. They would be glycosylated in the Golgi apparatus D. They might travel to the nucleus in a transport vesicle with a specific zip code.

D

Hemophilia is caused by several genetic factors; one, a recessive allele of an x-linked gene, is the subject of this problem, Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? A. 1/16 B. 1/8 C. 1/4 D. 1/2 E. 3/4

B

Homologous chromosomes A. Are identical B. Carry information for the same traits C. Carry the same alleles D. Align on the metaphase plate in meiosis II

C

How are Okazaki fragments synthesized? A. Using the leading strand template, and synthesizing 5' to 3' B. Using the leading strand template, and synthesizing 3' to 5' C. Using the lagging strand template, and synthesizing 5' to 3' D. Using the lagging strand template, and synthesizing 3' to 5'

C

If you could engineer an activity into DNA polymerase to allow both strands to follow the replication fork, what would this additional activity be? A. the ability to begin DNA synthesis without a primer B. The ability to proof read in the 5' to 3' direction C. The ability to synthesize DNA in the 3' to 5' direction D. the ability to synthesize DNA without using a template.

B

Intergrins are integral membrane proteins. They often attached to A. The membranes of intracellular organelles B. Cytoskeletal proteins and proteins in the extracellular matrix C. The outside of the plasma membrane D. glycogen molecules and other types of cellular inclusions.

Mitosis

Meiosis II is similar to?

C

Meiosis results in a reassortment of maternal and paternal chromosomes. If n=3 for a given organism, there are eight different combinations of paternal and maternal chromosomes. If no crossing over occurs, what is the probability that a gamete will receive only paternal chromosomes? A. 0 B. 1/16 C. 1/8 D. 1/3

D

Mendels rules do not correctly predict patterns of inheritance for tightly linked genes or the inheritance of alleles that show incomplete dominance. Does this mean his hypotheses are incorrect? A. Yes, because they are relevant only to a small number of organisms and traits. B. Yes, because not all data support his hypothesis C. No, because he was not aware of meiosis or the chromosome theory of inheritance. D. No, it just meant that his hypotheses are limited to certain conditions.

C

One of the possibilities that researchers interested in the genetic code considered was that the code was overlapping meaning that a single base could be part of up to three codons. How many amino acids would be encoded in the sequence 5' AUGUUAACGGAAU 3' by a non-over lapping and maximally overlapping code? A. 4 (non-overlapping) and 16 (overlapping) B. 4 and 12 C. 4 and 10 D. 12 and 4

A

Predict what would occur in a bacterial mutant that lost the ability to chemically mark the template strand of DNA. A. The mutation rate would increase B. The ability of DNA polymerase to discriminate between correct and incorrect base pairs would decrease. C. The energy differences between correct and incorrect base would decrease D. The energy difference between correct and incorrect base pairs would increase.

D

Progression through the cell cycle is regulated by oscillations in the concentration of which type of molecule? A. p53, Rb, and other tumor suppressor s B. Receptor tyrosine kinases C. Cyclin dependent kinases D. Cyclins

C

Protein Kinase is an enzyme that A. Functions as a second messenger molecule B. Serves as a receptor for various signal molecules C. Activates or inactivates other proteins by adding a phosphate group to them D. Produces second messenger molecules

D

Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubular tracks along which energy vesicles could be transported, and they added vesicles and ATP. Yet when they put everything together there was no movement or transport of vesicles. What were they missing? A. An axon B. Contractile microfilaments C. Endoplasmic Reticulum D. Motor proteins

B

Scientists have found that polypeptides that are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. What is/are possible explanations for the greater length of these polypeptides? A. The ribosomes that function as free ribosomes function differently than the ribosomes that are attached to the endoplasmic reticulum B. The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing. C. The amino acid sequence helps the endoplasmic reticulum package these proteins for shipping to the Golgi. D. the protein has a different function in the cytosol than in the endoplasmic reticulum.

A

The alleles found in haploid organisms cannot be dominant or recessive, why? A. Dominance and recessiveness describe which allele is expressed in phenotype when different alleles occur in the same individual B. Because only one allele is present, alleles in haploid organisms are always dominant. C. Alleles in haploid individuals are transmitted like mitochondrial DNA or chloroplast DNA D. Most haploid individuals are bacteria, and bacterial genetics is completely different from eukaryotic genetics.

B

The artificial sweetener nutrasweet consists of a phenylalanine molecule linked to aspartic acid. The labels of diet sodas that contain nutrasweet include a warning to people with PKU, why? A. Nutrasweet stimulates the same taste receptors that natural sugars do. B. People with PKU have to avoid phenylalanine in their diet C. In people with PKU, phenylalanine reacts with aspartic acid to form a toxic compound. D. People with PKU cannot lead normal lives, even if their environment is controlled.

C

The diploid number of a round worm species is 4. You have a male and female roundworm that are planning a family. Assuming there is no crossover, and random segregation of homologues during meiosis, how many different possible combinations of chromosomes might there be in the offspring? A. 4 B. 8 C. 16 D. 64

Topoisomerase

The enzyme that removes twists in DNA ahead of the replication fork is?

A

The genes for the traits that Mendel worked with are either located on different chromosomes or so far apart on the same chromosome that crossing over almost always occurs between them. How did this circumstance help Mendel recognize the principle of independent assortment. A. Otherwise, his dihybrid crosses would not have produced a 9:3:3:1 ratio of F2 phenotypes B. The occurrence of individuals with unexpected phenotypes led him to the discovery of recombination. C. It led him to the realization that the behavior of chromosomes during meiosis explained his result. D. It meant that the alleles involved were either dominant or recessive, which gave 3:1 ratios in the F1 generation.

D

What characteristics do tight junctions bestow on tissues that use these adhesions to connect adjacent cells? A. They allow communication between adjacent cells B. They provide strong connections to resist pulling forces. C. They use the extracellular matrix to indirectly connect adjacent cells. D. They form a watertight barrier between the cell.

C

The receptors for steroid hormones are located inside the cell, instead of on the membrane surface like most other signal receptors. Why is this not a problem for steroids? A. Because the receptors can be readily stimulated to exit and relocate on the membrane surface B. Because receptors located inside cells are less susceptible to blockage by inhibitors located on or near the cell surface, so it serves as a protective mechanism C. Because steroid hormones are lipid soluble so can readily diffuse through the lipid bilayer of the cell membrane. D. Because the receptors are repressible, meaning they are actively altering cell function unless the target hormone is present.

B

What does it mean to say that a signal is transduced? A. The signal enters the cell directly and binds to a receptor inside B. The physical form of the signal changes between the outside of a cell and the inside C. The signal is amplified, such that even a single molecule evokes a large response. D. The signal triggers a sequence of phosphorylation events inside the cell.

D

The variation among offspring, and the fact that they are genetically different from their parents, is not due to which of the following A. Random alignment of homologues during prophase 1 B. Crossing over C. Fertilization D. Random alignment of sister chromatids in metaphase II

A

Treating dissociated cells with certain antibodies makes the cells unable to reaggregate. Why? A. The antibodies bind to cell adhesion proteins B. The antibodies bind to the fiber component of the extracellular matrix. C. The antibodies bind to the cell surface and inhibit motility D. The antibodies acts as enzymes break down desmosomes.

A

What are homologous chromosomes? A. Chromosomes that are similar in their size, shape, and gene content. B. Similar chromosomes that are found in different individuals of the same species. C. The two threads in a replicated chromosome (they are identical copies). D. The products of crossing over, which contain a combination of segments from maternal chromosomes and segments from paternal chromosomes.

D

What aspect of DNA structure makes it possible for the enzymes of nucleotide excision repair to recognize many different types of DNA damage.

B

What can you infer about a high molecular weight protein that cannot be transported into the nucleus? A. It is too large B. It lacks a nuclear localization signal C. It contains errors in its amino acid sequence D. It lacks a signal sequence

B

What does it mean to say that a signal is transduced? A. The signaling molecule enters the cell directly and binds to a receptor inside. B. The physical form of the signal changes between the outside of the cell and the inside. C. The signal is amplified, such that even a single molecule evokes a large response. D. The signal triggers a sequence of phosphorylation events inside the cell.

D

What does it mean to say that a strands in a double helix are antiparallel? A. Their primary sequences consist of a sequence of complementary bases. B. They each have a sugar-phosphate backbone C. They each have a 5' to 3' directionality D. They have opposite directionality, or polarity

D

What does the one gene, one enzyme hypothesis state? A. Genes are composed of stretches of DNA B. Genes are made of protein C. Genes code for ribosomes D. A single gene codes for a single protein

C

What is a major difference between meiosis II and mitosis A. Homologues align on the metaphase plate in meiosis II B. Sister chromatids separate in mitosis, and homologues separate in meiosis II C. Meiosis II takes place in a haploid cell, while mitosis takes place in a diploid cell D. Crossover takes place in meiosis II

A

What is a major difference between mitosis and meiosis 1 A. Sister chromatids separate in mitosis, and homologues separate in meiosis 1. B. DNA replication takes place prior to mitosis, but not before meiosis 1 C. Sister chromatids separate in mitosis, and homologues separate in meiosis 2 D. Only meiosis 1 results in daughter cells that contain identical genetic information

B

What is an outcome of genetic recombination? A. the synapsing of homologs during prophase of meiosis I B. The new combination of maternal and paternal chromosome segments that results when homologs crossover C. the new combination of chromosome segments that result when self-fertilization occurs. D. The combination of a haploid phase and a diploid phase in a life cycle.

B

What is bivalent? A. The X that forms when chromatids from homologous chromosomes cross over. B. A group of four chromatids produced when homologs synapse C. The four points where homologous chromosomes touch as they synapse D. The group of four genetically identical daughter cells produced by mitosis.

A

What is meant by the claim that Mendel worked with the simplest possible genetic system? A. Discrete traits, two alleles, simple dominance and recessiveness, no sex chromosomes, and unlinked genes are the simplest situation known. B. the ability to self-fertilize or cross-pollinate made it simple for Mendel to set up controlled crosses C. Mendel was aware of meiosis and the chromosome theory of inheritance, so it was easy to reach the conclusions he did. D. Mendel' experimental designs and his rules of inheritance are actually neither complex nor sophisticated.

B

What is the function of primase? A. Synthesis of the short section of double stranded DNA required by DNA polymerase B. Synthesis of a short RNA, complementary to single stranded DNA C. Closing the gap at the 3' end of DNA after excision repair. D. Removing primers and synthesizing a short section of DNA to replace them.

A

What is the function of the nuclear pore complex that is found in all eukaryotes? A. It regulates the movement of all molecules into and out of the nucleus B. It synthesizes the proteins required to copy DNA and make mRNA C. It selectively transports molecules out of the nucleus, but prevents all inbound molecules from entering the nucleus. D. It assembles ribosomes from raw materials that are synthesized in the nucleus.

B

What is the major difference between the ECM of a plant cell and the ECM of an animal cell. A. Plant ECM is composed primarily of proteins, whereas animal ECM is mainly carbohydrates B. Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins C. Plant and animal ECMs are quite similar in structure and function D. ECM components in plant cells are released extracellularly by the Golgi stacks, whereas lysosomes do this in animal cells

C

What major events occur during anaphase of mitosis? A. Chromosomes replicate, so each chromosome consists of two identical sister chromatids B. Chromosomes condense and the nuclear envelope disappears. C. Sister chromatids separate, and the spindle poles are pushed farther apart. D. The chromosomes end up at opposite ends of the cell, and two nuclear envelopes form around them.

1/2

What proportion of chromosomes in a human skin cell are paternal chromosomes?

D

What would be the impact on the structure of a plant tissue if the cells lacked the ability to modify the extracellular environment? A. Cells would swell and burst if placed in a hypotonic environment. B. Cells would not be able to adhere to one another C. No defined tissues, consisting of similar cells with coordinated activities, would be possible. D. All of the above

B

Which of the following cell structures would you expect to be most important in the growth of bacteria on the surface of your teeth? A. Cell wall B. Fimbriae C. Flagella D. Cilia

D

Which of the following describes an important experimental strategy in deciphering the genetic code? A. Comparing the amino acid sequences of proteins with the base sequence of their genes B. Analyzing the sequence of RNAs produced from known DNA sequences C. Analyzing mutants that changed the code D. Examining the polypeptides produced when RNAs of known sequence were translated

A

Which of the following is an important exception to the central dogma of molecular biology? A. Many genes code for RNAs that function directly in the cell. B. DNA is the repository of genetic information in all cells C. Messenger RNA is short lived information carrier D. Proteins are responsible for most aspects of the phenotype

C

Which of the following is not a characteristic that chloroplasts and mitochondria share? A. They both have their own DNA B. They both have multiple membranes C. They are both part of the endomembrane system D. They are both capable of reproducing themselves.

A

Which of the following is not a property of DNA polymerase? A. It adds dNTPs only in the 5' to 3' direction B. It requires a primer to work C. It is associated with a sliding clamp only on the leading strand D. It's exonuclease activity is involved in proofreading

D

Which of the following is the strongest evidence that a trait might be influenced by polygenic inheritance? A. F1 offspring of parents with different phenotypes have an intermediate phenotype B. F1 offspring of parents with different phenotypes have the dominant phenotype. C. The trait shows qualitative (discrete) variation D. The trait shows quantitative variation.

D

You have a distant cousin age 4 who is always tired and fatigued and is not able to play games and sports like other healthy children. He most likely has an enzyme deficiency or defect associated with which intercellular organelle? A. Lysosomes B. Golgi apparatus C. Ribosomes D. Mitochondria

B

Which of the following statements represents a fundamental difference between the fibers found in the extracellular layers of plants and those of animals? A. Plant fibers resist compression forces, animal fibers resist pulling forces. B. Animal fibers consist of proteins, plant fibers consist of polysaccharides instead C. Plant extracellular fibers never move, animal fibers can slide past one another D. Cellulose microfibrils run parallel to one another, collagen filaments crisscross.

B

Which of the following statements would best describe a cell that has an extensive area of smooth endoplasmic reticulum? A. It plays a role in storage B. It synthesizes large quantities of lipids C. It actively exports protein molecules D. It is able to both import and export protein molecules

B

Which statement about the daughter cells following mitosis and cytokinesis is correct? A. They are genetically different from each other and from the parent cell B. They are genetically identical with each other and with the parent cell C. They are genetically identical with eachother but different from the parent cell D. Only one of the two daughter cells is genetically identical with the parent cell.

C

Why are lysosomes considered a part of the endomembrane system? A. Because they deposit end products of digestion in the endoplasmic reticulum B. Because they facilitate movement between stacks of Golgi C. Because they are formed from products sythesized by the endoplasmic reticulum and processed by the Golgi D. Because they are composed largely of phospholipids

D

Why can you infer that individuals that are pure line are homozygous for the gene in question? A. Because they are highly inbred B. Because only two alleles are present at each gene in the populations to which these individuals belong. C. Because in a pure line, phenotypes are not affected by environmental conditions or gene interactions. D. Because no other phenotype is ever observed in a pure-line population, this implies that only one allele is present.

C

Why does a single-base deletion mutation within a protein-coding sequence usually have a more severe effect than a deletion of three adjacent bases? A. because single-base deletions prevent the ribosome from binding to mRNA B. Because single base deletions stabilize mRNA C. Because single base deletions change the reading frame D. Because single base deletions alter the meaning of individual codons.

A

Why is smooth endoplasmic reticulum unable to synthesize proteins? A. Because it has no ribosomes B. Because there is no supply of free amino acids C. Because it stores calcium which is a known inhibitor of protein synthesis D. Because it has no DNA to direct synthesis of proteins

B

Why is the allele for wrinkled seed shape in garden peas considered recessive? A. It "recedes" in the F2 generation when homozygous parents are crossed. B. The trait associated with the allele is not expressed in heterozygotes. C. Individuals with the allele have lower fitness than that of individuals with the dominant allele. D. the allele is less common that the dominant allele (the wrinkle is a rare mutant).