Biology Exit Exam Questions

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that

a) humans and chimpanzees share a relatively recent common ancestor.

b) humans evolved from chimpanzees.

c) chimpanzees evolved from humans.

d) convergent evolution led to the DNA similarities.

e) humans and chimpanzees are not closely related.

a

325) It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that

a) island forms and mainland forms descended from common ancestors.

b) common environments are inhabited by the same organisms.

c) the islands were originally part of the continent.

d) the island forms and mainland forms are converging.

e) island forms and mainland forms have identical gene pools.

a

324) Of the following anatomical structures, which is homologous to the wing of a bird?

a) Dorsal fin of a shark

b) Hindlimb of a kangaroo

c) Wing of a butterfly

d) Tail fin of a flying fish

e) Flipper of a cetacean

E

323) In Darwin's thinking, the more closely related two different organisms are, the

a) more similar their habitats are.

b) less similar their DNA sequences are.

c) more recently they shared a common ancestor.

d) less likely they are to have the same genes in common.

e) more similar they are in size.

C

322) Charles Darwin was the first person to propose

a) that evolution occurs.

b) a mechanism for how evolution occurs.

c) that the Earth is older than a few thousand years.

d) a mechanism for evolution that was supported by evidence.

e) a way to use artificial selection as a means of domesticating plants and animals.

D

321) Which of these naturalists synthesized a concept of natural selection independently of Darwin?

a) Charles Lyell

b) Gregor Mendel

c) Alfred Wallace

d) John Henslow

e) Thomas Malthus

B

319) Tropical grasslands with scattered trees are also known as

a) taigas.

b) tundras.

c) savannas.

d) chaparrals.

e) temperate plains.

C

318) Which biome is able to support many large animals despite receiving moderate amounts of rainfall?

a) tropical rain forest

b) temperate forest

c) chaparral

d) taiga

e) savanna

E

317) Which of the following organisms is the most likely candidate for geographic isolation?

a) sparrow

b) bat

c) squirrel

d) salt-water fish

e) land snail

E

316) The main reason polar regions are cooler than the equator is because

a) there is more ice at the poles.

b) sunlight strikes the poles at an lower angle.

c) the poles are farther from the sun.

d) the poles have a thicker atmosphere.

e) the poles are permanently tilted away from the sun.

B

315) Which of the following is responsible for the summer and winter stratification of deep temperate lakes?

a) Water is densest at 4°C.

b) Oxygen is most abundant in deeper waters.

c) Winter ice sinks in the summer.

d) Stratification is caused by a thermocline.

e) Stratification always follows the fall and spring turnovers.

A

314) In temperate lakes, the surface water is replenished with nutrients during turnovers that occur in the

a) autumn and spring.

b) autumn and winter.

c) spring and summer.

d) summer and winter.

e) summer and autumn.

A

313) Which of the following abiotic factors has the greatest influence on the metabolic rates of plants and animals?

a) water

b) wind

c) temperature

d) rocks and soil

e) disturbances

C

312) Which of the following are important biotic factors that can affect the structure and organization of biological communities?

a) precipitation, wind

b) nutrient availability, soil pH

c) predation, competition

d) temperature, water

e) light intensity, seasonality

C

311) Which statement best contrasts environmentalism with ecology?

a) Ecology is the study of the environment; environmentalism is the study of ecology.

b) Ecology provides scientific understanding of living things and their environment; environmentalism is more about conservation and preservation of life on Earth.

c) Environmentalists are only involved in politics and advocating for protecting nature; ecologists are only involved in scientific investigations of the environment.

d) Ecologists study organisms in environments that have been undisturbed by human activities; environmentalists study the effects of human activities on organisms.

e) Environmentalism is devoted to applied ecological science; ecology is concerned with basic/theoretical ecological science.

B

310) Ecology as a discipline directly deals with all of the following levels of biological organization except

a) population.

b) cellular.

c) organismal.

d) ecosystem.

e) community.

B

309) Which of the following levels of organization is arranged in the correct sequence from most to least inclusive?

a) community, ecosystem, individual, population

b) ecosystem, community, population, individual

c) population, ecosystem, individual, community

d) individual, population, community, ecosystem

e) individual, community, population, ecosystem

B

308) Which of the following statements about ecology is incorrect?

a) Ecologists may study populations and communities of organisms.

b) Ecological studies may involve the use of models and computers.

c) Ecology is a discipline that is independent from natural selection and evolutionary history.

d) Ecology spans increasingly comprehensive levels of organization, from individuals to ecosystems.

e) Ecology is the study of the interactions between biotic and abiotic aspects of the environment.

C

307) Which of the following obtain energy by oxidizing inorganic substances; energy that is used, in part, to fix CO2?

a) photoautotrophs

b) photoheterotrophs

c) chemoautotrophs

d) chemoheterotrophs that perform decomposition

e) parasitic chemoheterotrophs

C

306) Which of the following use light energy to synthesize organic compounds from CO2?

a) photoautotrophs

b) photoheterotrophs

c) chemoautotrophs

d) chemoheterotrophs that perform decomposition

e) parasitic chemoheterotrophs

A

305) Cyanobacteria are

a) photoautotrophs.

b) photoheterotrophs.

c) chemoautotrophs.

d) chemoheterotrophs that perform decomposition.

e) parasitic chemoheterotrophs.

A

304) Which of the following contains a copy of the chromosome, along with a small amount of dehydrated cytoplasm, within a tough wall?

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

A

303) If this structure connects the cytoplasm of two bacteria, one of these cells may gain new genetic material:

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

B

302) Which of the following is an important source of endotoxin in gram-negative species?

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

D

301) Which of the following is a structure that permits conjugation to occur?

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

B

300) Not present in all bacteria, this structure enables those that possess it to germinate after exposure to harsh conditions, such as boiling:

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

A

299) Not present in all bacteria, this cell covering enables cells that possess it to resist the defenses of host organisms:

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

E

298) Which of the following requires ATP to function, and permits some species to respond to taxes (plural of taxis)?

a) endospore

b) sex pilus

c) flagellum

d) cell wall

e) capsule

C

297) Which statement about the genomes of prokaryotes is correct?

a) Prokaryotic genomes are diploid throughout most of the cell cycle.

b) Prokaryotic chromosomes are sometimes called plasmids.

c) Prokaryotic cells have multiple chromosomes, "packed" with a relatively large amount of protein.

d) The prokaryotic chromosome is not contained within a nucleus but, rather, is found at the nucleoid region.

e) Prokaryotic genomes are composed of linear DNA (that is, DNA existing in the form of a line with two ends).

E

296) Prokaryotic ribosomes differ from those present in eukaryotic cytosol. Because of this, which of the following is correct?

a) Some selective antibiotics can block protein synthesis of bacteria without effects on protein synthesis in the eukaryotic host.

b) Eukaryotes did not evolve from prokaryotes.

c) Translation can occur at the same time as transcription in eukaryotes but not in prokaryotes.

d) Some antibiotics can block the synthesis of peptidoglycan in the walls of bacteria.

e) Prokaryotes are able to use a much greater variety of molecules as food sources than can eukaryotes.

A

295) The typical prokaryotic flagellum features

a) an internal 9 + 2 pattern of microtubules.

b) an external covering provided by the plasma membrane.

c) a complex "motor" embedded in the cell wall and plasma membrane.

d) a basal body that is similar in structure to the cell's centrioles.

C

294) Which of these is the most common compound in the cell walls of gram-positive bacteria?

a) cellulose

b) lipopolysaccharide

c) lignin

d) peptidoglycan

e) protein

D

293) Which statement about bacterial cell walls is false?

a) Bacterial cell walls differ in molecular composition from plant cell walls.

b) Cell walls prevent cells from bursting in hypotonic environments.

c) Cell walls prevent cells from dying in hypertonic conditions.

d) Bacterial cell walls are similar in function to the cell walls of many protists, fungi, and plants.

e) Cell walls provide the cell with a degree of physical protection from the environment.

C

292) Which is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell?

a) plasma membrane

b) capsule

c) cell wall

d) nucleoid region

e) pili

A

291) Mycoplasmas are bacteria that lack cell walls. On the basis of this structural feature, which statement concerning mycoplasmas should be true?

a) They are gram-negative.

b) They are subject to lysis in hypotonic conditions.

c) They lack a cell membrane as well.

d) They undergo ready fossilization in sedimentary rock.

e) They possess typical prokaryotic flagella.

B

290) Emerging viruses arise by

a) mutation of existing viruses.

b) the spread of existing viruses to new host species.

c) the spread of existing viruses more widely within their host species.

d) all of the above

e) none of the above

D

289) Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

a) metabolism

b) ribosomes

c) genetic material composed of nucleic acid

d) cell division

e) independent existence

C

288) Antiviral drugs that have become useful are usually associated with which of the following properties?

a) ability to remove all viruses from the infected host

b) interference with the viral reproduction

c) prevention of the host from becoming infected

d) removal of viral proteins

e) removal of viral mRNAs

B

287) Which of the following is the best predictor of how much damage a virus causes?

a) ability of the infected cell to undergo normal cell division

b) ability of the infected cell to carry on translation

c) whether the infected cell produces viral protein

d) whether the viral mRNA can be transcribed

e) how much toxin the virus produces

A

286) What are prions?

a) misfolded versions of normal brain protein

b) tiny molecules of RNA that infect plants

c) viral DNA that has had to attach itself to the host genome

d) viruses that invade bacteria

e) a mobile segment of DNA

A

285) What is the function of reverse transcriptase in retroviruses?

a) It hydrolyzes the host cell's DNA.

b) It uses viral RNA as a template for DNA synthesis.

c) It converts host cell RNA into viral DNA.

d) It translates viral RNA into proteins.

e) It uses viral RNA as a template for making complementary RNA strands.

B

284) What is the name given to viruses that are single-stranded RNA that acts as a template for DNA synthesis?

a) retroviruses

b) proviruses

c) viroids

d) bacteriophages

e) lytic phages

A

283) Why do RNA viruses appear to have higher rates of mutation?

a) RNA nucleotides are more unstable than DNA nucleotides.

b) Replication of their genomes does not involve the proofreading steps of DNA replication.

c) RNA viruses replicate faster.

d) RNA viruses can incorporate a variety of nonstandard bases.

e) RNA viruses are more sensitive to mutagens.

B

281) Which of the following terms describes bacteriophage DNA that has become integrated into the host cell chromosome?

a) intemperate bacteriophages

b) transposons

c) prophages

d) T-even phages

e) plasmids

C

280) Which of the following is characteristic of the lytic cycle?

a) Many bacterial cells containing viral DNA are produced.

b) Viral DNA is incorporated into the host genome.

c) The viral genome replicates without destroying the host.

d) A large number of phages is released at a time.

e) The virus-host relationship usually lasts for generations.

D

279) Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of life?

a) re-infection by a closely related herpesvirus of a different strain

b) re-infection by the same herpesvirus strain

c) co-infection with an unrelated virus that causes the same symptoms

d) copies of the herpesvirus genome permanently maintained in host nuclei

e) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

D

278) Which of the following molecules make up the viral envelope?

a) glycoproteins

b) proteosugars

c) carbopeptides

d) peptidocarbs

e) carboproteins

A

277) Why are viruses referred to as obligate parasites?

a) They cannot reproduce outside of a host cell.

b) Viral DNA always inserts itself into host DNA.

c) They invariably kill any cell they infect.

d) They can incorporate nucleic acids from other viruses.

e) They must use enzymes encoded by the virus itself.

A

276) The host range of a virus is determined by

a) the proteins on its surface and that of the host.

b) whether its nucleic acid is DNA or RNA.

c) the proteins in the host's cytoplasm.

d) the enzymes produced by the virus before it infects the cell.

e) the enzymes carried by the virus.

A

275) Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

a) a base-pair deletion

b) a codon substitution

c) a substitution in the last base of a codon

d) a codon deletion

e) a point mutation

A

274) A frameshift mutation could result from

a) a base insertion only.

b) a base deletion only.

c) a base substitution only.

d) deletion of three consecutive bases.

e) either an insertion or a deletion of a base.

E

273) Sickle-cell disease is probably the result of which kind of mutation?

a) point

b) frameshift

c) nonsense

d) nondisjunction

e) both B and D

A

272) What is the most abundant type of RNA?

a) mRNA

b) tRNA

c) rRNA

d) pre-mRNA

e) hnRNA

C

271) In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?

a) the sequence of the intron that immediately precedes each exon

b) the number of polypeptides making up the functional protein

c) the various domains of the polypeptide product

d) the number of restriction enzyme cutting sites

e) the number of start sites for transcription

C

270) Alternative RNA splicing

a) is a mechanism for increasing the rate of transcription.

b) can allow the production of proteins of different sizes from a single mRNA.

c) can allow the production of similar proteins from different RNAs.

d) increases the rate of transcription.

e) is due to the presence or absence of particular snRNPs.

B

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

a) protein

b) DNA

c) RNA

d) lipid

e) sugar

C

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

a) introns

b) exons

c) codons

d) replicons

e) transposons

B

267) What is a ribozyme?

a) an enzyme that uses RNA as a substrate

b) an RNA with enzymatic activity

c) an enzyme that catalyzes the association between the large and small ribosomal subunits

d) an enzyme that synthesizes RNA as part of the transcription process

e) an enzyme that synthesizes RNA primers during DNA replication

B

266) Which of the following help(s) to stabilize mRNA by inhibiting its degradation?

a) TATA box

b) spliceosomes

c) 5' cap and poly (A) tail

d) introns

e) RNA polymerase

C

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

a) the protein product of the promoter

b) start and stop codons

c) ribosomes and tRNA

d) several transcription factors (TFs)

e) aminoacyl synthetase

D

264) In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

a) ligase

b) RNA polymerase I

c) RNA polymerase II

d) RNA polymerase III

e) primase

C

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

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

b) If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA.

c) If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide.

d) If several codons are found to translate to the same amino acid, such as serine.

e) If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites.

A

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

a) proteins, triglycerides, and testosterone

b) proteins, ATP, and DNA

c) ATP, RNA, and DNA

d) alpha glucose, ATP, and DNA

e) proteins, carbohydrates, and ATP

C

261) Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because

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

b) enzymes are made of DNA, and affected individuals lack DNA polymerase.

c) many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA.

d) certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

e) metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

A

260) Why do histones bind tightly to DNA?

a) Histones are positively charged, and DNA is negatively charged.

b) Histones are negatively charged, and DNA is positively charged.

c) Both histones and DNA are strongly hydrophobic.

d) Histones are covalently linked to the DNA.

e) Histones are highly hydrophobic, and DNA is hydrophilic.

A

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

a) primase

b) ligase

c) DNA polymerase

d) single-strand binding proteins

e) exonuclease

D

257) The leading and the lagging strands differ in that

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.

b) the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.

c) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.

d) the leading strand is synthesized at twice the rate of the lagging strand.

A

256) The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

a) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

b) the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups.

c) ATP contains three high-energy bonds; the nucleoside triphosphates have two.

d) ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells.

e) triphosphate monomers are active in the nucleoside triphosphates, but not in ATP.

A

255) Which of the following synthesizes short segments of RNA?

a) helicase

b) DNA polymerase III

c) ligase

d) DNA polymerase I

e) primase

E

254) Which of the following covalently connects segments of DNA?

a) helicase

b) DNA polymerase III

c) ligase

d) DNA polymerase I

e) primase

C

253) What is the function of DNA polymerase III?

a) to unwind the DNA helix during replication

b) to seal together the broken ends of DNA strands

c) to add nucleotides to the end of a growing DNA strand

d) to degrade damaged DNA molecules

e) to rejoin the two DNA strands (one new and one old) after replication

C

252) Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?

a) The prokaryotic chromosome has histones, whereas eukaryotic chromosomes do not.

b) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

c) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.

d) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.

e) Prokaryotes have telomeres, and eukaryotes do not.

B

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

a) hydrogen

b) ionic

c) covalent

d) sulfhydryl

e) phosphate

A

250) Why does the DNA double helix have a uniform diameter?

a) Purines pair with pyrimidines.

b) C nucleotides pair with A nucleotides.

c) Deoxyribose sugars bind with ribose sugars.

d) Nucleotides bind with nucleosides.

e) Nucleotides bind with nucleoside triphosphates.

A

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

a) The viral DNA will be radioactive.

b) The viral proteins will be radioactive.

c) The bacterial DNA will be radioactive.

d) both A and B

e) both A and C

B

248) Which of the following investigators was/were responsible for the following discovery? Phage 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.

a) Frederick Griffith

b) Alfred Hershey and Martha Chase

c) Oswald Avery, Maclyn McCarty, and Colin MacLeod

d) Erwin Chargaff

e) Matthew Meselson and Franklin Stahl

E

247) In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

a) DNA contains sulfur, whereas protein does not.

b) DNA contains phosphorus, but protein does not.

c) DNA contains nitrogen, whereas protein does not.

d) DNA contains purines, whereas protein includes pyrimidines.

e) RNA includes ribose, while DNA includes deoxyribose sugars.

B

246) What does transformation involve in bacteria?

a) the creation of a strand of DNA from an RNA molecule

b) the creation of a strand of RNA from a DNA molecule

c) the infection of cells by a phage DNA molecule

d) the type of semiconservative replication shown by DNA

e) assimilation of external DNA into a cell

E

245) The frequency of Down syndrome in the human population is most closely correlated with which of the following?

a) Frequency of new meiosis

b) Average of the ages of mother and father

c) Age of the mother

d) Age of the father

e) Exposure of pregnant women to environmental pollutants

C

244) Women with Turner syndrome have a genotype characterized as which of the following?

a) aabb

b) Mental retardation and short arms

c) A karyotype of 45, X

d) A karyotype of 47, XXX

e) A deletion of the Y chromosome

C

243) A cell that has 2n + 1 chromosomes is

a) trisomic.

b) monosomic.

c) euploid.

d) polyploid.

e) triploid.

A

242) New combinations of linked genes are due to which of the following?

a) Nondisjunction

b) Crossing over

c) Independent assortment

d) Mixing of sperm and egg

e) Deletions

B

241) Calico cats are female because

a) a male inherits only one of the two X-linked genes controlling hair color.

b) the males die during embryonic development.

c) the Y chromosome has a gene blocking orange coloration.

d) only females can have Barr bodies.

e) multiple crossovers on the Y chromosome prevent orange pigment production.

A

240) SRY is best described in which of the following ways?

a) A gene region present on the Y chromosome that triggers male development

b) A gene present on the X chromosome that triggers female development

c) An autosomal gene that is required for the expression of genes on the Y chromosome

d) An autosomal gene that is required for the expression of genes on the X chromosome

e) Required for development, and males or females lacking the gene do not survive past early childhood

A

239) What is the chromosomal system of sex determination in most species of ants and bees?

a) Haploid-diploid

b) X-0

c) X-X

d) X-Y

e) Z-W

A

238) What is the chromosomal system for sex determination in birds?

a) Haploid-diploid

b) X-0

c) X-X

d) X-Y

e) Z-W

E

237) Why did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics?

a) It revealed new and unanticipated features of Mendel's pea plant varieties.

b) It allowed the study of meiosis and mitosis, revealing parallels between behaviors of genes and chromosomes.

c) It allowed scientists to see the DNA present within chromosomes.

d) It led to the discovery of mitochondria.

e) It showed genes functioning to direct the formation of enzymes.

B

236) When a disease is said to have a multifactorial basis, it means that

a) both genetic and environmental factors contribute to the disease.

b) it is caused by a gene with a large number of alleles.

c) it affects a large number of people.

d) it has many different symptoms.

e) it tends to skip a generation.

A

235) People with sickle-cell trait

a) are heterozygous for the sickle-cell allele.

b) are usually healthy.

c) have increased resistance to malaria.

d) produce normal and abnormal hemoglobin.

e) All of the above

E

234) Which describes the ABO blood group system?

a) Incomplete dominance

b) Multiple alleles

c) Pleiotropy

d) Epistasis

B

233) Which describes the ability of a single gene to have multiple phenotypic effects?

a) Incomplete dominance

b) Multiple alleles

c) Pleiotropy

d) Epistasis

C

232) Given the parents AABBCc × AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?

a) 1/4

b) 1/8

c) 3/4

d) 3/8

e) 1

C

231) In a cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?

a) 1/4

b) 1/8

c) 1/16

d) 1/32

e) 1/64

E

230) Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?

a) Synapsis of homologous chromosomes

b) Crossing over

c) Alignment of tetrads at the equator

d) Separation of homologs at anaphase

e) Separation of cells at telophase

C

229) Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

a) Prophase I of meiosis

b) Prophase II of meiosis

c) Metaphase I of meiosis

d) Anaphase I of meiosis

e) Anaphase of mitosis

D

228) How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

a) 4

b) 8

c) 16

d) 32

e) 64

B

227) What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

a) There is considerable genetic variation in garden peas.

b) Traits are inherited in discrete units, and are not the results of "blending."

c) Recessive genes occur more frequently in the F1 than do dominant ones.

d) Genes are composed of DNA.

e) An organism that is homozygous for many recessive traits is at a disadvantage.

B

226) What is the difference between a monohybrid cross and a dihybrid cross?

a) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.

b) A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny.

c) A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid only one.

d) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.

e) A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.

C

225) Pea plants were particularly well suited for use in Mendel's breeding experiments for all of the following reasons except that

a) peas show easily observed variations in a number of characters, such as pea shape and flower color.

b) it is possible to control matings between different pea plants.

c) it is possible to obtain large numbers of progeny from any given cross.

d) peas have an unusually long generation time.

e) many of the observable characters that vary in pea plants are controlled by single genes.

D

224) A tetrad includes which of the following sets of DNA strands?

a) Two single-stranded chromosomes that have synapsed

b) Two sets of sister chromatids that have synapsed

c) Four sets of sister chromatids

d) Four sets of unique chromosomes

e) Eight sets of sister chromatids

B