Biology test 3 questions

Which of the following represents a bond between a purine and a pyrimidine, respectively? A) C-T B) G-A C) G-C D) T-A E) A-G

C) G-C

Homologous chromosomes undergo crossing over during A. prophase I of meiosis. B. prophase II of meiosis. C. prophase I and II of meiosis. D. prophase I of mitosis. E. anaphase II of meiosis.

A. prophase I of meiosis.

Interphase involves all of the following except A. the condensation of chromatin. B. DNA replication. C. the synthesis of cellular components necessary for mitosis. D. G2 E. G1

A. the condensation of chromatin.

If codons were read two bases at a time instead of three bases at a time, how many different possible amino acids could be specified? A) 16 B) 64 C) 8 D) 32 E) 128

A) 16

Which of the following statements about the pattern of inheritance for a rare dominant allele is true? A) Every affected person has an affected parent. B) Unaffected parents can produce children who are affected. C) Affected parents do not produce affected children. D) Unaffected mothers have sons who are affected and daughters who are carriers. E) None of the above

A) Every affected person has an affected parent.

Which of the following statements about DNA replication is false? A) Okazaki fragments are synthesized as part of the leading strand. B) Replication forks represent areas of active DNA synthesis on the chromosomes. C) Error rates for DNA replication are reduced by proofreading of the DNA polymerase. D) Ligases and polymerases function in the vicinity of replication forks. E) The sliding clamp protein increases the rate of DNA synthesis.

A) Okazaki fragments are synthesized as part of the leading strand.

Which of the following statements about meiosis is true? A) The chromosome number in the resulting cells is halved. B) DNA replication occurs before meiosis I and again before meiosis II. C) The homologs pair during prophase II. D) The daughter cells are genetically identical to the parental cell. E) The chromosome number of the resulting cells is the same as that of the parent cell.

A) The chromosome number in the resulting cells is halved.

Which of the following statements about true-breeding plants is true? A) When a true-breeding plant with a particular trait is crossed with another plant of the same variety, all of their offspring produce plants with that same trait. B) When a true-breeding plant with a particular trait is crossed with another plant of the same variety, all of their offspring will be sterile. C) They result from a monohybrid cross. D) They result from a dihybrid cross. E) They result from crossing over during prophase I of meiosis.

A) When a true-breeding plant with a particular trait is crossed with another plant of the same variety, all of their offspring produce plants with that same trait.

The primary function of DNA polymerase is to A) add nucleotides to the growing daughter strand. B) seal nicks along the sugar-phosphate backbone of the daughter strand. C) unwind the parent DNA double helix. D) generate primers to initiate DNA synthesis. E) prevent reassociation of the denatured parental DNA strands.

A) add nucleotides to the growing daughter strand.

Proofreading and repair occur A) at any time during or after synthesis of DNA. B) only before mitosis. C) only in the presence of DNA polymerase. D) only during replication. E) None of the above

A) at any time during or after synthesis of DNA.

A test cross A) is used to determine if an organism that is displaying a dominant trait is heterozygous or homozygous for that trait. B) is used to determines if an organism that is displaying a recessive trait is heterozygous or homozygous for that trait. C) causes the loss of hybrid vigor. D) results in an F2 generation with a phenotypic ratio of 3 4 dominant to 1 4 recessive. E) results in the transfer of the same alleles from generation to generation.

A) is used to determine if an organism that is displaying a dominant trait is heterozygous or homozygous for that trait.

If a high concentration of a particular nucleotide lacking a hydroxyl group at the 3' end is added to a PCR reaction, A) no additional nucleotides will be added to a growing strand containing that nucleotide. B) strand elongation will proceed as normal. C) nucleotides will be added only at the 5' end. D) T. aquaticus DNA polymerase will become nonfunctional. E) the primer will be unable to bind with the DNA template.

A) no additional nucleotides will be added to a growing strand containing that nucleotide.

What fraction of offspring of the cross Aa × Aa is homozygous for the dominant allele? A. 1⁄4 B. 1⁄64 C. 1⁄16 D. 1⁄32 E. 1⁄8

A. 1⁄4

If guanine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be cytosine? A. 20 B. 40 C. 30 D. 60 E. 15

A. 20

Which statement about linkage of genes is false? A. Genes on the same chromosome assort independently. B. Genes on the same chromosome are said to be linked. C. Crossing over results in recombinant phenotypes. D. Genes on the same chromosome that are far apart have a higher recombination frequency than those that are close together. E. Crossing over between two linked genes can alter phenotypes of progeny.

A. Genes on the same chromosome assort independently.

Which of the following statements about aneuploidy is false? A. It does not occur in humans. B. Trisomies are common in human zygotes. C. It results from chromosomal nondisjunction. D. Aneuploidy results when a piece of one chromosome translocates to another chromosome. E. An individual with an extra chromosome is trisomic.

A. It does not occur in humans.

Lateral gene transfer between individuals of a species A. can result in bacterial strains resistant to antibiotics. B. always involves recombination. C. occurs only with plasmid DNA. D. occurs by sexual reproduction in bacteria. E. does not occur in bacteria.

A. can result in bacterial strains resistant to antibiotics.

In order to show that DNA in cell extracts is responsible for genetic transformation in of bacteria, important corroborating evidence should indicate that _______ also destroyed transforming activity. A. enzymes that hydrolyzed DNA B. enzymes that hydrolyze RNA C. enzymes that hydrolyzed proteins D. boiling E. enzymes that hydrolyzed polysaccharides

A. enzymes that hydrolyzed DNA

Anaphase A. is the phase when sister chromatids separate and move to opposite poles. B. involves chromosomes lining up at the equatorial plate. C. occurs before the nuclear envelope breaks down. D. takes place just before cytokinesis. E. Both a and c

A. is the phase when sister chromatids separate and move to opposite poles.

If 30 percent of the bases in a sample of DNA extracted from eukaryotic cells are adenine, what percentage of the bases in this DNA are cytosine? A) 10 percent B) 20 percent C) 30 percent D) 40 percent E) 50 percent

B) 20 percent

Translation of messenger RNA into protein occurs in a _______ direction, and from the _______ terminus to the _______ terminus. A) 3-to-5; N; C B) 5-to-3; N; C C) 3-to-5; C; N D) 5-to-3; C; N E) 3-to-5; C; C

B) 5-to-3; N; C

If the following synthetic RNA were added to a test tube containing all the components necessary for protein translation to occur, what would the amino acid sequence be? 5-AUAUAUAUAUAU-3 A) Polyphenylalanine B) Isoleucine-tyrosine-isoleucine-tyrosine C) Isoleucine-isoleucine-isoleucine-isoleucine D) Tyrosine-tyrosine-tyrosine-tyrosine E) Aspargine-aspargine-aspargine-aspargine

B) Isoleucine-tyrosine-isoleucine-tyrosine

Which of the following statements about RNA polymerase is false? A) It synthesizes mRNA in a 5-to-3 direction, reading the DNA strand 3 to 5. B) It synthesizes mRNA in a 3-to-5 direction, reading the DNA strand 5 to 3. C) It binds at the promoter and unwinds the DNA. D) It does not require a primer to initiate transcription. E) It uses only one strand of DNA as a template for synthesizing RNA

B) It synthesizes mRNA in a 3-to-5 direction, reading the DNA strand 5 to 3.

Translate the following mRNA: 3-GAUGGUUUUAAAGUA-5 A) NH2 met—lys—phe—leu—stop COOH B) NH2 met—lys—phe—trp—stop COOH C) NH2 asp—gly—phe—lys—val COOH D) NH2 met—gly—phe—lys—val COOH E) NH2 asp—gly—phe—lys—stop COOH

B) NH2 met—lys—phe—trp—stop COOH

Which of the following statements about the pattern of inheritance for a rare recessive allele is true? A) Every affected person has an affected parent. B) Unaffected parents can produce children who are affected. C) Affected parents do not produce affected children. D) Unaffected mothers have affected sons and daughters who are carriers. E) None of the above

B) Unaffected parents can produce children who are affected.

Gain-of-function mutations A) are dominant mutations that are expressed in wild-type cells. B) are dominant mutations that are expressed in mutant cells. C) are the cause of continuous division in cancer cells. D) can be analyzed only under restrictive conditions. E) are expressed only in response to the appropriate environmental signals.

B) are dominant mutations that are expressed in mutant cells.

Sex determination is similar in humans and Drosophila because in both species A) females are hemizygous. B) males have one X chromosome and females have two X chromosomes. C) all males have one Y chromosome. D) secondary sex characteristics are determined by genes on the X chromosome. E) the ratio of X chromosomes to sets of autosomes determines maleness or femaleness.

B) males have one X chromosome and females have two X chromosomes.

RNA primers are necessary in DNA synthesis because A) DNA polymerase is unable to initiate replication without an origin. B) the DNA polymerase enzyme can catalyze the addition of deoxyribonucleotides only onto the 3' (—OH) end of an existing strand. C) RNA primase is the first enzyme in the replication complex. D) primers mark the sites where helicase has to unwind the DNA. E) All of the above

B) the DNA polymerase enzyme can catalyze the addition of deoxyribonucleotides only onto the 3' (—OH) end of an existing strand.

The telomeres at the ends of linear chromosomes allow A) the 5' ends of the chromosomes to undergo recombination. B) the gaps left by primer removal of lagging strands to be repaired by telomerase. C) DNA repair enzymes to recognize those ends and remove them. D) normal cells to divide continuously. E) DNA breaks to be examined at cell division checkpoints.

B) the gaps left by primer removal of lagging strands to be repaired by telomerase.

Suppose unattached earlobes are a dominant trait. Phil and Maggie both have unattached earlobes but their daughter, Celia, does not. If Phil and Maggie have a second child, what is the probability that it will have attached earlobes? A. 3⁄4 B. 1⁄4 C. 1⁄2 D. 1⁄8 E. 1

B. 1⁄4

What fraction of the offspring of the cross AaBb × AaBb would show the dominant phenotypes for both genes? A. 12⁄16 B. 9⁄16 C. 1⁄3 D. 6⁄16 E. 3⁄16

B. 9⁄16

_______ is the term for when heterozygous offspring have superior fitness than their homozygous parents. A. Linkage B. Heterosis C. Codominance D. Incomplete dominance E. Epistasis

B. Heterosis

Which of the following mutations is not a chromosomal mutation? A. Inversions B. Point mutations C. Duplications D. Translocations E. Large deletions

B. Point mutations

Mutations A. are always deleterious. B. can arise from errors in DNA replication. C. are of no importance to evolution. D. are always caused by mutagens. E. occur at the same rate for all bases.

B. can arise from errors in DNA replication.

Translocations A. cannot be passed to offspring. B. can occur in mitotic cells. C. are not likely to affect gene expression. D. are the breaking and rejoining of chromatids of homologous chromosomes. E. are rare.

B. can occur in mitotic cells.

A mutant strain of yeast grew well at 20°C, but not at 37°C, whereas the wild-type strain grew well at both temperatures. The mutation is an example of a A. point mutation. B. conditional mutation C. missense mutation. D. frame-shift mutation. E. gain-of-function mutation.

B. conditional mutation.

Which of the following is not used for DNA synthesis? A. dCTP B. dUTP C. dGTP D. dTTP E. dATP

B. dUTP

Genes located on mitochondrial DNA are usually inherited A. randomly. B. from the mother. C. from the father. D. by independent assortment. E. evenly from both the mother and the father.

B. from the mother.

The 5′ end of a DNA strand A. could contain the base, uridine. B. is part of the growing strand during DNA replication. C. is the end of both strands of DNA in a double helix. D. does not contain a phosphate group on the ribose. E. is part of the template strand during DNA replication.

B. is part of the growing strand during DNA replication.

The fact that a trait like height in humans varies over a wide range of values is due to A. penetrance. B. multiple alleles and the environmental influences on the expression of these genes. C. discrete and qualitative genomic variation. D. expressivity. E. epistasis.

B. multiple alleles and the environmental influences on the expression of these genes.

In many animals, including humans, sex is determined by a single _______, or by a pair of them. Both males and females have two copies of each of the rest of the chromosomes, which are called _______. A. autosome; sex chromosomes B. sex chromosome; autosomes C. allele; genes D. gene; sex chromosomes E. gene; autosomes

B. sex chromosome; autosomes

In multicellular organisms A. all mutations are point mutations. B. somatic mutations may be passed to daughter cells by mitosis. C. somatic mutations are passed on to offspring produced by sexual reproduction. D. meiosis is not required for the transmission of germ line mutations to the next generation. E. all mutations produce phenotypic changes.

B. somatic mutations may be passed to daughter cells by mitosis.

The 9:3:3:1 ratio is obtained A. through a dihybrid cross in which the genes are linked on the same chromosome. B. through a dihybrid cross in which the genes are on different chromosomes. C. when crossing over occurs. D. in a test cross. E. None of the above

B. through a dihybrid cross in which the genes are on different chromosomes.

After DNA replication, each chromosome has _______ molecule(s) of DNA called _______, that after separation are known as _______ chromosomes. A. two; daughter chromosomes; sister B. two; sister chromatids; daughter C. four; sister chromatids; daughter D. two; daughter chromatids; sister E. four; sister chromosomes; daughter

B. two; sister chromatids; daughter

Which of the following chromosomal mutations would still allow protein X to be functional? A) Deletion of the last 100 codons of gene X B) A duplication of gene X C) An inversion of the last 100 codons of gene X D) A translocation of the last 100 codons of gene X to another chromosome E) None of the above

C) An inversion of the last 100 codons of gene X

Which part of the tRNA base-pairs with the codon in the mRNA? A) The 3 end, where the amino acid is covalently attached B) The 5 end C) The anticodon D) The start codon E) The promoter

C) The anticodon

Which of the following statements about chiasmata is true? A) They are sites where nonsister chromatids can exchange genetic material during meiosis and increase genetic variation in gametes. B) They are sites where sister chromatids can exchange genetic material during meiosis and increase genetic variation in gametes. C) They increase genetic variation among the gametes due to exchange between all members of the tetrad during meiosis. D) They increase genetic variation among the gametes due to exchange between all members of the tetrad during mitosis. E) All of the above

C) They increase genetic variation among the gametes due to exchange between all members of the tetrad during meiosis.

The difference between asexual and sexual reproduction is that A) asexual reproduction occurs only in bacteria, whereas sexual reproduction occurs in plants and animals. B) asexual reproduction results from meiosis, whereas sexual reproduction results from mitosis. C) asexual reproduction results in an organism that is identical to the parent, whereas sexual reproduction results in an organism that is not identical to either parent. D) asexual reproduction results from the fusion of two gametes, whereas sexual reproduction produces clones of the parent organism. E) asexual reproduction occurs only in haplontic organisms, whereas sexual reproduction occurs only in diplontic organisms.

C) asexual reproduction results in an organism that is identical to the parent, whereas sexual reproduction results in an organism that is not identical to either parent.

Programmed cell death (apoptosis) A) occurs in cells that have been deprived of essential nutrients. B) occurs only in cells that have damaged DNA. C) is a natural process during development. D) is signaled by the initiation of mitosis. E) is well controlled in cancer cells.

C) is a natural process during development.

. Transcription in prokaryotic cells A) occurs in the nucleus, whereas translation occurs in the cytoplasm. B) is initiated at a start codon with the help of initiation factors and the small subunit of the ribosome. C) is initiated at a promoter and uses only one strand of DNA (the template strand) to synthesize a complementary RNA strand. D) is terminated at a stop codon. E) is initiated at an ori site on the chromosome.

C) is initiated at a promoter and uses only one strand of DNA (the template strand) to synthesize a complementary RNA strand.

A fundamental requirement for the functioning of genetic material is that it must be A) conserved among all organisms with very little variation. B) passed intact from one species to another. C) replicated accurately and passed from a parent to its offspring or from a cell to its daughter cells. D) found outside the nucleus. E) replicated accurately over many millions of years of evolution.

C) replicated accurately and passed from a parent to its offspring or from a cell to its daughter cells.

If the ori site on the E. coli chromosome is deleted, A) nothing will happen. B) replication will start but not be able to continue. C) replication will not start. D) replication will be initiated at another ori site on the chromosome. E) the chromosome will be replicated but the cell will not be able to divide.

C) replication will not start.

The PCR technique A) can amplify only very small samples of DNA. B) amplifies several random DNA sequences within a genome. C) requires synthetic primers to flank the regions of interest. D) is accomplished in three sequential steps: binding, denaturation, and replication. E) generates DNA molecules that all have variable sequences.

C) requires synthetic primers to flank the regions of interest.

The terms "penetrance" and "expressivity" refer to A) the increased expression of a particular trait when a hybrid species is formed. B) quantitative traits that diminish or intensify a particular phenotype. C) the influence of environment on the expression of a particular genotype. D) the expression of one gene masking the effects of another gene. E) the expression of a dominant phenotype in a heterozygote.

C) the influence of environment on the expression of a particular genotype.

A diploid cell in G1 has _______ micrograms of DNA as one of its daughter cells at the end of meiosis I and _______ number of chromosomes as one of its daughter cells at the end of meiosis II. A) twice the number of; the same B) one-half the number of; twice the C) the same number of; twice the D) one-half the number of; the same E) the same number of; one-half the

C) the same number of; twice the

Which of the following statements about repairing errors in DNA replication is false? A. During DNA replication, guanine may be incorrectly paired with thymine, requiring repair. B. DNA polymerase I replaces the removed section of DNA with the correct bases. C. DNA topoisomerase repairs the remaining nicks in the newly replicated strand. D. During DNA replication, DNA polymerase proofreads the growing strand and replaces incorrectly paired nucleotides before continuing replication. E. After replication, mismatch repair proteins excise a small portion of the DNA molecule that includes the mismatched bases.

C. DNA topoisomerase repairs the remaining nicks in the newly replicated strand.

Which of the following statements about DNA structure is false? A. It is a double-stranded helix. B. It has a uniform diameter. C. The 3′ end is phosphorylated. D. It is a right-handed helix. E. It is antiparallel (the two strands run in opposite directions).

C. The 3′ end is phosphorylated.

DNA replication occurs A. only before meiosis. B. during chromosome condensation. C. before both mitosis and meiosis. D. during G2. E. only before mitosis.

C. before both mitosis and meiosis.

Human papilloma virus (HPV) infection of the tissues lining the cervix A. has a gene that codes for a growth factor receptor. B. results in inhibition of cell division. C. codes for a protein that inactivates the retinoblastoma protein. D. activates a tumor suppressor. E. activates an oncogene

C. codes for a protein that inactivates the retinoblastoma protein.

Coat color in rabbits involves the effects of multiple gene interactions. If a rabbit has two recessive alleles (cc) for coat color, it is always albino no matter what the genotype of other genes involved in coat color. This is an example of A. incomplete dominance. B. codominance. C. epistasis. D. pleiotropy. E. heterosis.

C. epistasis.

In sexually reproducing organisms, the diploid phase of the life cycle begins at A. spore formation. B. meiosis. C. fertilization. D. mitosis. E. gamete formation.

C. fertilization.

A point mutation A. is a result of a chromosomal deletion. B. does not occur in noncoding regions of DNA. C. is a change in a single nucleotide of DNA. D. is always silent. E. is not transmitted to daughter cells.

C. is a change in a single nucleotide of DNA.

In meiosis, as opposed to mitosis, A. genetically identical daughter cells are produced. B. crossing over cannot take place. C. pairing of homologous chromosomes occurs. D. only two daughter cells are formed. E. there is no cytokinesis.

C. pairing of homologous chromosomes occurs.

The mitotic spindle A. plays a role in cytokinesis. B. is composed of two different types of microtubules. C. provides the force needed for chromosome movement. D. is composed of intermediate filaments. E. begins to form during metaphase.

C. provides the force needed for chromosome movement.

Incomplete dominance A. causes epistasis. B. occurs only in X-linked genes. C. results in a phenotypic ratio of 1:2:1 in the F2 generation from a monohybrid cross. D. is the same as codominance. E. involves the distinct expression of both alleles, as in the ABO blood group system.

C. results in a phenotypic ratio of 1:2:1 in the F2 generation from a monohybrid cross.

A silent mutation A. is a result of a change in a codon for an amino acid in a protein to a stop codon. B. results in a shorter mRNA transcript of the gene. C. would likely not affect the activity of a protein. D. results in a protein that is truncated from the N-terminal end. E. would not affect the primary structure of a protein.

C. would likely not affect the activity of a protein.

Quantitative traits are traits A) that are affected by the environment. B) that affect the same physical characteristic. C) in which each allele intensifies or diminishes the phenotype. D) All of the above E) None of the above

D) All of the above

Which of the following statements about DNA replication and cytokinesis in Escherichia coli is true? A) DNA replication occurs in the nucleus. B) Cytokinesis is facilitated by microfilaments of actin and myosin. C) DNA replication occurs during the S phase of the cell cycle. D) Cell reproduction is initiated by reproductive signals, which lead to DNA replication, DNA segregation, and cytokinesis. E) The E. coli chromosome is linear.

D) Cell reproduction is initiated by reproductive signals, which lead to DNA replication, DNA segregation, and cytokinesis.

Before Mendel, genetic inheritance was thought to be a function of the blending of traits from the two parents. Which exception to Mendel's laws is in fact an example of blending? A) X linkage B) Polygenic inheritance C) Incomplete dominance D) Codominance E) Pleiotropism

D) Codominance

Which of the following would not be found in a DNA molecule? A) Purines B) Ribose sugars C) Phosphates D) Sulfur E) Nitrogenous bases

D) Sulfur

What would happen if a mutation occurred in DNA such that the second codon of the resulting mRNA was changed from UGG to UAG? A) Translation would continue and the second amino acid would be the same. B) Nothing. The ribosome would skip that codon and translation would continue. C) Translation would continue, but the reading frame of the ribosome would be shifted. D) Translation would stop at the second codon, and no functional protein would be made. E) Translation would continue, but the second amino acid in the protein would be different.

D) Translation would stop at the second codon, and no functional protein would be made.

Which of the following statements about the pattern of inheritance for a sex-linked allele is true? A) Every affected person has an affected parent. B) Unaffected parents can produce children who are affected. C) Affected parents do not produce affected children. D) Unaffected mothers have sons who are affected and daughters who are carriers. E) None of the above

D) Unaffected mothers have sons who are affected and daughters who are carriers.

Epistasis is A) the degree to which a particular genotype is expressed in an individual. B) the proportion of individuals within a group that have a particular genotype and show the expected phenotype. C) a situation in which a heterozygotic individual expresses phenotypic traits that are intermediate between those of the parents. D) a situation in which one gene masks the expression of another gene. E) a situation in which both alleles are expressed equally.

D) a situation in which one gene masks the expression of another gene.

Linked genes are genes that A) assort independently. B) segregate equally in the gametes during meiosis. C) always contribute the same trait to the zygote. D) are found on the same chromosome. E) recombine during mitosis.

D) are found on the same chromosome.

Cytoplasmic inheritance A) results from polygenic nuclear traits. B) is determined by nuclear genes. C) is the result of the gametes' contributions of equal amounts of cytoplasm to the zygote. D) is determined by genes on DNA molecules in mitochondria and chloroplasts. E) follows Mendel's law of segregation.

D) is determined by genes on DNA molecules in mitochondria and chloroplasts.

Hemophilia is a trait carried by the mother and passed to her sons. The allele for hemophilia, therefore, A) is carried on one of the mother's autosomal chromosomes. B) is carried on the Y chromosome. C) can be carried on the X or Y chromosome. D) is on the X chromosome and can be inherited by the son only if the mother is a carrier (heterozygous). E) is carried in the mitochondrial genome because a son inherits this allele from his mother.

D) is on the X chromosome and can be inherited by the son only if the mother is a carrier (heterozygous).

Which stage of mitosis includes the formation of kinetochores? A. Interphase B. Telophase C. Anaphase D. Prophase E. Metaphase

D. Prophase

Codominance A. involves one allele having more than one phenotypic effect. B. occurs when heterozygotes show a phenotype intermediate between those of the two homozygotes. C. is only found in mammalian enzyme production. D. involves the expression of both alleles at a locus producing two different phenotypes. E. would result in pink flowers from a cross between white and red flowers.

D. involves the expression of both alleles at a locus producing two different phenotypes.

What is the probability that a cross between a true-breeding pea plant with spherical seeds and a true-breeding pea plant with wrinkled seeds will produce F1 progeny with spherical seeds? A) 1/2 B) 1/4 C) 0 D) 1/8 E) 1

E) 1

Imagine that there is a mutation in a Cdk gene such that its gene product is present but nonfunctional. What kind of effect would this mutation have on a mammalian white blood cell based on what you know about Cdk and protein RB interactions? A) The cell would be unable to replicate its DNA. B) The cell would be unable to enter mitosis. C) The cell would be unable to reproduce itself. D) The cell would not be able to phosphorylate its associated cyclin. E) All of the above

E) All of the above

Watson and Crick's model allowed them to visualize A) the molecular bonds of DNA. B) the sugar and phosphate component of the DNA molecule's surface. C) how the purines and pyrimidines fit together in a double helix. D) the antiparallel design of two strands of the DNA double helix. E) All of the above

E) All of the above

When the lagging daughter strand of DNA is synthesized, unreplicated gaps are formed on the parental DNA. Lagging strand synthesis fills these gaps by A) synthesizing short Okazaki fragments in a 5'-to-3' direction. B) synthesizing multiple short RNA primers to initiate DNA replication. C) using DNA polymerase I to remove RNA primers from Okazaki fragments. D) filling in those gaps with new strands of complementary DNA as the replication fork proceeds. E) All of the above

E) All of the above

Which of the following statements about kinetochores on mitotic chromosomes is true? A) They are located at the centromere of each chromosome. B) They are the sites where microtubules attach to separate the chromosomes. C) They are organized so that there is one per sister chromatid. D) Kinetochore microtubules from opposite poles attach to each sister chromatid. E) All of the above

E) All of the above

Which of the following statements about mitosis is true? A) Cytokinesis follows mitosis. B) DNA replication is completed prior to the beginning of this phase. C) The chromosome number of the resulting cells is the same as that of the parent cell. D) The daughter cells are usually genetically identical to the parental cell. E) All of the above

E) All of the above

Which of the following statements about chromatids is true? A) They are replicated chromosomes still joined together at the centromere. B) They are identical in mitotic chromosomes. C) They undergo recombination in mitosis. D) They are identical in meiotic chromosomes. E) Both a and b

E) Both a and b

Peptidyl transferase is an A) enzyme found in the nucleus of the cell that assists in the transfer of mRNA to the cytoplasm. B) enzyme that adds the amino acid to the 3' end of the tRNA. C) enzyme found in the large subunit of the ribosome that catalyzes the formation of the peptide bond in the growing polypeptide. D) RNA molecule that is catalytic. E) Both c and d

E) Both c and d

Which of the following statements about the mitotic spindle is true? A) It is composed of polar and kinetochore microtubules, both of which attach to chromosomes. B) It is composed of actin and myosin microfilaments. C) It is composed of kinetochores at the metaphase plate. D) It is composed of microtubules, which help separate the chromosomes to opposite poles of the cell. E) It originates only at the centrioles in the centrosomes.

E) It originates only at the centrioles in the centrosomes.

Imagine that there is a mutation in the cyclin gene such that its gene product is nonfunctional. What kind of effect would this mutation have on a skin cell in the area of a cut? A) Cdk would not be synthesized. B) There would be no effect, because skin cells do not replicate. C) The cell would be stuck in S phase and unable to replicate. D) The cell would not be able to enter G1. E) The cell would be unable to reproduce itself.

E) The cell would be unable to reproduce itself.

Chargaff observed that the amount of _______ was roughly equal to the amount of _______ in all tested organisms. A) purines; pyrimidines B) A; T C) A + T; G + C D) A + G; T + C E) a, b, and d

E) a, b, and d

Chromosome movement during anaphase is the result of A) the hydrolysis of ATP by dynein. B) molecular motors at the kinetochores that move the chromosomes toward the poles. C) molecular motors at the centrosome that pull the microtubules toward the poles. D) shortening of the microtubules at the centrosome that pull the chromosomes toward the poles. E) a, b, and d

E) a, b, and d

A chromatid is A) a chromosome before it has undergone DNA replication. B) one of the pairs of homologous chromosomes. C) a homologous chromosome. D) a newly replicated bacterial chromosome. E) one-half of a newly replicated eukaryotic chromosome.

E) one-half of a newly replicated eukaryotic chromosome.

A bacterial cell's genotype can be altered by A) the introduction of a plasmid that carries some of the bacteria's genes. B) mating with a bacterial cell with the same genotype. C) homologous recombination with human DNA. D) the forming of a conjugation tube with another bacterial cell. E) the transferring of genetic material from a different strain of bacteria.

E) the transferring of genetic material from a different strain of bacteria.

A dramatic departure from expected phenotypic ratios may be the result of A. environmental influences. B. genetic linkage. C. epistasis. D. heterosis. E. All of the above

E. All of the above

The replication of lagging strands of DNA differs from the replication of leading strands in that A. DNA is replicated as short fragments. B. RNA primers are required. C. DNA ligase is needed. D. primase is required. E. All of the above

E. All of the above

Which of the following statements about cyclin-dependent kinases (Cdk's) or cyclin is false? A. Phosphorylated retinoblastoma protein is inactive. B. Cdk's use ATP as a substrate. C. Different Cdk's act at different points in the cell cycle. D. A Cdk can catalyze the phosphorylation of retinoblastoma protein. E. Cyclin is made continuously during the cell cycle.

E. Cyclin is made continuously during the cell cycle.

Which of the following statements about asexual reproduction in flowering plants is true? A. In asexual reproduction, two gametes fuse to produce a zygote. B. In asexual reproduction, there is genetic variation among the offspring. C. It requires meiosis. D. In asexual reproduction, progeny have half the number of chromosomes as the parent. E. It produces offspring that are genetically identical to the parent.

E. It produces offspring that are genetically identical to the parent.

A-T base pairs in a DNA double helix A. are more heat stable than G-C base pairs. B. are not accessible to DNA binding proteins. C. form three hydrogen bonds with each other. D. are of a different length than G-C base pairs. E. are chemically distinct from G-C base pairs.

E. are chemically distinct from G-C base pairs.

The cross AaBb × AaBb is an example of a _______ cross; the results of such crosses led Mendel to propose what we now call the law of _______. A. dihybrid; segregation of genes B. test; segregation of genes C. self-; segregation of genes D. test; independent assortment E. dihybrid; independent assortment

E. dihybrid; independent assortment

Apoptosis A. is triggered solely by signals external to the cell. B. occurs only in animals. C. occurs only during development. D. is the same process as necrosis. E. is controlled by signal transduction pathways.

E. is controlled by signal transduction pathways.

In many eukaryotes, there are repetitive sequences at the ends of chromosomes called telomeres. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand. A. leading; replicase B. lagging; DNA polymerase I C. leading; telomerase D. leading; DNA polymerase I E. lagging; telomerase

E. lagging; telomerase