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Test sobre Biology I - Exam 4, creado por acbridges91 el 10/05/2015.

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Biology I - Exam 4

Pregunta 1 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • DNA contains sulfur, whereas protein does not.

  • DNA contains phosphorus, whereas protein does not.

  • DNA contains purines, whereas protein includes pyrimidines.

  • DNA contains nitrogen, whereas protein does not.

Explicación

Pregunta 2 de 100

1

Which of the following investigators was (were) responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Selecciona una de las siguientes respuestas posibles:

  • Oswald Avery, Maclyn McCarty, and Colin MacLeod

  • Matthew Meselson and Franklin Stahl

  • Alfred Hershey and Martha Chase

  • Erwin Chargaff

Explicación

Pregunta 3 de 100

1

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?

Selecciona una de las siguientes respuestas posibles:

  • side groups of nitrogenous bases

  • sequence of bases

  • phosphate-sugar backbones

  • complementary pairing of bases

Explicación

Pregunta 4 de 100

1

In an analysis of the nucleotide composition of DNA, which of the following will be found?

Selecciona una de las siguientes respuestas posibles:

  • A + C = G + T

  • A = G and C = T

  • A = C

  • G + C = T + A

Explicación

Pregunta 5 de 100

1

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _____ of the last nucleotide in the polymer.

Selecciona una de las siguientes respuestas posibles:

  • the 3' OH

  • a nitrogen from the nitrogen-containing base

  • the 5' phosphate

  • C6

Explicación

Pregunta 6 de 100

1

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?

Selecciona una de las siguientes respuestas posibles:

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

  • Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.

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

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

Explicación

Pregunta 7 de 100

1

What is meant by the description "antiparallel" regarding the strands that make up DNA?

Selecciona una de las siguientes respuestas posibles:

  • The twisting nature of DNA creates nonparallel strands.

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

  • One strand contains only purines and the other contains only pyrimidines.

  • Base pairings create unequal spacing between the two DNA strands.

Explicación

Pregunta 8 de 100

1

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

Selecciona una de las siguientes respuestas posibles:

  • Replication will require a DNA template from another source.

  • No replication fork will be formed.

  • Replication will occur via RNA polymerase alone.

  • Additional proofreading will occur.

Explicación

Pregunta 9 de 100

1

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

Selecciona una de las siguientes respuestas posibles:

  • helicase

  • primase

  • DNA ligase

  • DNA polymerase III

Explicación

Pregunta 10 de 100

1

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

Selecciona una de las siguientes respuestas posibles:

  • the evolution of telomerase enzyme

  • DNA polymerase that cannot replicate the leading strand template to its 5' end

  • gaps left at the 5' end of the lagging strand

  • gaps left at the 3' end of the lagging strand because of the need for a primer

Explicación

Pregunta 11 de 100

1

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

Selecciona una de las siguientes respuestas posibles:

  • It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.

  • It causes specific double-strand DNA breaks that result in blunt ends on both strands.

  • It adds a single 5' cap structure that resists degradation by nucleases.

  • It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

Explicación

Pregunta 12 de 100

1

The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects _____.

Selecciona una de las siguientes respuestas posibles:

  • a critical function of telomeres

  • that new mutations in telomeres have been advantageous

  • the low frequency of mutations occurring in this DNA

  • continued evolution of telomeres

Explicación

Pregunta 13 de 100

1

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that _____.

Selecciona una de las siguientes respuestas posibles:

  • ATP contains three high-energy bonds; the nucleoside triphosphates have two

  • the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups

  • the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose

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

Explicación

Pregunta 14 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • DNA polymerase begins adding nucleotides at the 5' end of the template

  • the polarity of the DNA molecule prevents addition of nucleotides at the 3' end

  • replication must progress toward the replication fork

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

Explicación

Pregunta 15 de 100

1

What is the function of topoisomerase?

Selecciona una de las siguientes respuestas posibles:

  • unwinding of the double helix

  • relieving strain in the DNA ahead of the replication fork

  • stabilizing single-stranded DNA at the replication fork

  • elongating new DNA at a replication fork by adding nucleotides to the existing chain

Explicación

Pregunta 16 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • It unwinds the parental double helix.

  • It stabilizes the unwound parental DNA.

  • It joins Okazaki fragments together.

  • It synthesizes RNA nucleotides to make a primer.

Explicación

Pregunta 17 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • single-strand DNA binding proteins

  • DNA polymerase

  • ligase

  • primase

Explicación

Pregunta 18 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • a high probability of somatic cells becoming cancerous

  • a reduction in chromosome length in gametes

  • an inability to repair thymine dimers

  • an inability to produce Okazaki fragments

Explicación

Pregunta 19 de 100

1

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____.

Selecciona una de las siguientes respuestas posibles:

  • determines the tertiary structure of a DNA molecule

  • permits complementary base pairing

  • allows variable width of the double helix

  • determines the type of protein produced

Explicación

Pregunta 20 de 100

1

Semiconservative replication involves a template. What is the template?

Selecciona una de las siguientes respuestas posibles:

  • one strand of the DNA molecule

  • an RNA molecule

  • single-stranded binding proteins

  • DNA polymerase

Explicación

Pregunta 21 de 100

1

DNA is synthesized through a process known as _____.

Selecciona una de las siguientes respuestas posibles:

  • conservative replication

  • semiconservative replication

  • transcription

  • translation

Explicación

Pregunta 22 de 100

1

Who performed classic experiments that supported the semiconservative model of DNA replication?

Selecciona una de las siguientes respuestas posibles:

  • Franklin and Wilkins

  • Watson and Crick

  • Hershey and Chase

  • Meselson and Stahl

Explicación

Pregunta 23 de 100

1

DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?

Selecciona una de las siguientes respuestas posibles:

  • deoxyribonucleotide triphosphates

  • DNA polymerase

  • ribozymes

  • ATP

Explicación

Pregunta 24 de 100

1

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

Selecciona una de las siguientes respuestas posibles:

  • DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semi-conservative.

  • Prokaryotic replication does not require a primer.

  • DNA polymerases of prokaryotes can add nucleotides to both 3' and 5' ends of DNA strands, while those of eukaryotes function only in the 5' → 3' direction.

  • Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

Explicación

Pregunta 25 de 100

1

What is a telomere?

Selecciona una de las siguientes respuestas posibles:

  • the ends of linear chromosomes

  • DNA replication during telophase

  • the site of origin of DNA replication

  • the mechanism that holds two sister chromatids together

Explicación

Pregunta 26 de 100

1

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _____.

Selecciona una de las siguientes respuestas posibles:

  • 5' TCA 3'

  • 3' ACU 5'

  • 3' UCA 5'

  • 3' UGA 5'

Explicación

Pregunta 27 de 100

1

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

Selecciona una de las siguientes respuestas posibles:

  • The same codons in different organisms translate into different amino acids.

  • Different organisms have different types of amino acids.

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

  • DNA was the first genetic material.

Explicación

Pregunta 28 de 100

1

Which of the following contradicts the one-gene, one-enzyme hypothesis?

Selecciona una de las siguientes respuestas posibles:

  • Lactose intolerance is caused by a defective lactase gene.

  • A mutation in a single gene can result in a defective protein.

  • A single kinase gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally.

  • Alkaptonuria results when individuals lack a single enzyme involved in the catalysis of homogentisic acid.

Explicación

Pregunta 29 de 100

1

Which of the following specifies a single amino acid in a polypeptide chain?

Selecciona una de las siguientes respuestas posibles:

  • the complementarity of DNA and RNA

  • the three-base sequence of mRNA

  • the base sequence of the tRNA

  • the aminoacyl-tRNA synthetase

Explicación

Pregunta 30 de 100

1

In the process of transcription, _____.

Selecciona una de las siguientes respuestas posibles:

  • mRNA attaches to ribosomes

  • proteins are synthesized

  • RNA is synthesized

  • DNA is replicated

Explicación

Pregunta 31 de 100

1

Codons are part of the molecular structure of _____.

Selecciona una de las siguientes respuestas posibles:

  • a protein

  • mRNA

  • tRNA

  • rRNA

Explicación

Pregunta 32 de 100

1

What does it mean when we say the genetic code is redundant?

Selecciona una de las siguientes respuestas posibles:

  • The genetic code is universal (the same for all organisms).

  • The genetic code is different for different domains of organisms.

  • A single codon can specify the addition of more than one amino acid.

  • More than one codon can specify the addition of the same amino acid.

Explicación

Pregunta 33 de 100

1

Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukarotes?

Selecciona una de las siguientes respuestas posibles:

  • Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.

  • Proteins transfer information from the nucleus to the ribosome, where protein synthesis takes place.

  • Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis takes place.

  • DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a template for protein synthesis.

Explicación

Pregunta 34 de 100

1

According to the central dogma, what molecule should go in the blank?
DNA → _____ → Proteins

Selecciona una de las siguientes respuestas posibles:

  • mtDNA

  • mRNA

  • rRNA

  • tRNA

Explicación

Pregunta 35 de 100

1

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Selecciona una de las siguientes respuestas posibles:

  • Codons are a nearly universal language among all organisms.

  • Prokaryotic codons usually specify different amino acids than those of eukaryotes.

  • Prokaryotic codons usually contain different bases than those of eukaryotes.

  • The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes.

Explicación

Pregunta 36 de 100

1

Which of the following occurs in prokaryotes but not in eukaryotes?

Selecciona una de las siguientes respuestas posibles:

  • post-transcriptional splicing

  • concurrent transcription and translation

  • translation in the absence of a ribosome

  • gene regulation

Explicación

Pregunta 37 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • ribosomes and tRNA

  • several transcription factors

  • aminoacyl-tRNA synthetase

  • start and stop codons

Explicación

Pregunta 38 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • Its significance has not yet been determined.

  • It sets the reading frame of the mRNA.

  • It is the recognition site for a specific transcription factor.

  • It is the recognition site for ribosomal binding.

Explicación

Pregunta 39 de 100

1

A ribozyme is _____.

Selecciona una de las siguientes respuestas posibles:

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

  • an RNA with catalytic activity

  • a catalyst that uses RNA as a substrate

  • an enzyme that synthesizes RNA as part of the transcription process

Explicación

Pregunta 40 de 100

1

Which of the following is the first event to take place in translation in eukaryotes?

Selecciona una de las siguientes respuestas posibles:

  • the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

  • covalent bonding between the first two amino acids

  • base pairing of activated methionine-tRNA to AUG of the messenger RNA

  • binding of the larger ribosomal subunit to smaller ribosomal subunits

Explicación

Pregunta 41 de 100

1

A signal peptide _____.

Selecciona una de las siguientes respuestas posibles:

  • terminates translation of messenger RNA

  • directs an mRNA molecule into the cisternal space of the ER

  • helps target a protein to the ER

  • signals the initiation of transcription

Explicación

Pregunta 42 de 100

1

What must occur before a newly made polypeptide is secreted from a cell?

Selecciona una de las siguientes respuestas posibles:

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

  • Its signal sequence must be cleaved off before the polypeptide can enter the ER.

  • Its signal sequence must target it to the plasma membrane, where it causes exocytosis.

  • It must be translated by a ribosome that remains free within the cytosol.

Explicación

Pregunta 43 de 100

1

Translation requires _____.

Selecciona una de las siguientes respuestas posibles:

  • mRNA, tRNA, DNA, and rRNA

  • mRNA, tRNA, and rRNA

  • mRNA, DNA, and rRNA

  • mRNA, tRNA, and DNA

Explicación

Pregunta 44 de 100

1

During elongation, which site in the ribosome represents the location where a codon is being read?

Selecciona una de las siguientes respuestas posibles:

  • P site

  • A site

  • E site

  • the small ribosomal subunit

Explicación

Pregunta 45 de 100

1

Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?

Selecciona una de las siguientes respuestas posibles:

  • translocation

  • initiation

  • reading of the next codon of mRNA

  • The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken.

Explicación

Pregunta 46 de 100

1

Which one of the following, if missing, would usually prevent translation from starting?

Selecciona una de las siguientes respuestas posibles:

  • poly-A tail

  • exon

  • 5' cap

  • AUG codon

Explicación

Pregunta 47 de 100

1

How does termination of translation take place?

Selecciona una de las siguientes respuestas posibles:

  • The 5' cap is reached.

  • The end of the mRNA molecule is reached.

  • The poly-A tail is reached.

  • A stop codon is reached.

Explicación

Pregunta 48 de 100

1

Post-translational modifications of proteins may include the _____.

Selecciona una de las siguientes respuestas posibles:

  • addition of a 5 cap

  • addition of carbohydrates to form a glycoprotein

  • removal of introns

  • addition of a poly-A tail

Explicación

Pregunta 49 de 100

1

A nonsense mutation in a gene _____.

Selecciona una de las siguientes respuestas posibles:

  • has no effect on the amino acid sequence of the encoded protein

  • introduces a premature stop codon into the mRNA

  • alters the reading frame of the mRNA

  • changes an amino acid in the encoded protein

Explicación

Pregunta 50 de 100

1

Which of the following DNA mutations is most likely to damage the protein it specifies?

Selecciona una de las siguientes respuestas posibles:

  • an addition of three nucleotides

  • a base-pair deletion

  • a codon deletion

  • a substitution in the last base of a codon

Explicación

Pregunta 51 de 100

1

Which of the following defines a genome?

Selecciona una de las siguientes respuestas posibles:

  • the complete set of an organism's polypeptides

  • the complete set of a species' polypeptides

  • a karyotype

  • the complete set of an organism's genes and other DNA sequences

Explicación

Pregunta 52 de 100

1

Asexual reproduction occurs during _____.

Selecciona una de las siguientes respuestas posibles:

  • chromosome exchange between organisms of different species

  • fertilization

  • meiosis

  • mitosis

Explicación

Pregunta 53 de 100

1

Which of the following is a true statement about sexual vs. asexual reproduction?

Selecciona una de las siguientes respuestas posibles:

  • In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.

  • In asexual reproduction, offspring are produced by fertilization without meiosis.

  • Asexual reproduction produces only haploid offspring.

  • Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi.

Explicación

Pregunta 54 de 100

1

At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?

Selecciona una de las siguientes respuestas posibles:

  • metaphase

  • interphase

  • prophase

  • anaphase

Explicación

Pregunta 55 de 100

1

Which of the following is true of a species that has a chromosome number of 2n = 16?

Selecciona una de las siguientes respuestas posibles:

  • Each diploid cell has eight homologous pairs.

  • The species is diploid with 32 chromosomes per cell.

  • A gamete from this species has four chromosomes.

  • The species has 16 sets of chromosomes per cell.

Explicación

Pregunta 56 de 100

1

Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common?
I. Alternation of generations
II. Meiosis
III. Fertilization
IV. Gametes
V. Spores

Selecciona una de las siguientes respuestas posibles:

  • I, II, and IV

  • I, II, III, IV, and V

  • II, IV, and V

  • II, III, and IV

Explicación

Pregunta 57 de 100

1

A given organism has 23 pairs of homologs in its karyotype. Therefore, we can conclude that it must _____.

Selecciona una de las siguientes respuestas posibles:

  • be human

  • have gametes with 23 chromosomes

  • be an animal

  • reproduce sexually

Explicación

Pregunta 58 de 100

1

Homologous chromosomes _____.

Selecciona una de las siguientes respuestas posibles:

  • align on the metaphase plate in meiosis II

  • carry information for the same traits

  • carry the same alleles

  • are identical

Explicación

Pregunta 59 de 100

1

If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?

Selecciona una de las siguientes respuestas posibles:

  • fertilization

  • reverse transcription

  • synapsis

  • DNA replication

Explicación

Pregunta 60 de 100

1

The human X and Y chromosomes _____.

Selecciona una de las siguientes respuestas posibles:

  • are called autosomes

  • include genes that determine an individual's sex

  • are both present in every somatic cell of males and females

  • are the same size and have the same number of genes

Explicación

Pregunta 61 de 100

1

Which of these is a karyotype?

Selecciona una de las siguientes respuestas posibles:

  • the appearance of an organism

  • organized images of a cells chromosomes

  • a display of a cells mitotic stages

  • a display of all of the cell types in an organism

Explicación

Pregunta 62 de 100

1

The somatic cells of a privet shrub each contain 46 chromosomes. How do privet chromosomes differ from the chromosomes of humans ,who also have 46?

Selecciona una de las siguientes respuestas posibles:

  • Privet shrubs must be metabolically more like animals than like other shrubs.

  • Genes of privet chromosomes are significantly different than those in humans.

  • Privet sex cells have chromosomes that can synapse with human chromosomes in the laboratory.

  • Privet cells cannot reproduce sexually.

Explicación

Pregunta 63 de 100

1

After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.

Selecciona una de las siguientes respuestas posibles:

  • haploid, and the chromosomes are each composed of two chromatids

  • diploid, and the chromosomes are each composed of a single chromatid

  • diploid, and the chromosomes are each composed of two chromatids

  • haploid, and the chromosomes are each composed of a single chromatid

Explicación

Pregunta 64 de 100

1

Which of the following happens at the conclusion of meiosis I?

Selecciona una de las siguientes respuestas posibles:

  • Four daughter cells are formed.

  • The chromosome number per cell remains the same.

  • Homologous chromosomes of a pair are separated from each other.

  • Sister chromatids are separated.

Explicación

Pregunta 65 de 100

1

Which of the following can occur by the process of meiosis but not mitosis?

Selecciona una de las siguientes respuestas posibles:

  • Diploid cells form haploid cells.

  • A diploid cell combines with a haploid cell.

  • Haploid cells fuse to form diploid cells.

  • Haploid cells multiply into more haploid cells.

Explicación

Pregunta 66 de 100

1

Crossing over normally takes place during which of the following processes?

Selecciona una de las siguientes respuestas posibles:

  • meiosis I

  • meiosis II

  • mitosis

  • mitosis and meiosis II

Explicación

Pregunta 67 de 100

1

Homologous pairs of chromosomes align opposite of each other at the equator of a cell during _____.

Selecciona una de las siguientes respuestas posibles:

  • meiosis metaphase II

  • meiosis metaphase I

  • meiosis telophase II

  • mitosis metaphase

Explicación

Pregunta 68 de 100

1

Centromeres split and sister chromatids migrate to opposite poles in meiosis _____.

Selecciona una de las siguientes respuestas posibles:

  • telophase I

  • anaphase I

  • telophase II

  • anaphase II

Explicación

Pregunta 69 de 100

1

Independent assortment of chromosomes occurs during _____.

Selecciona una de las siguientes respuestas posibles:

  • mitosis and meiosis II

  • meiosis I only

  • meiosis II only

  • mitosis and meiosis I

Explicación

Pregunta 70 de 100

1

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

Selecciona una de las siguientes respuestas posibles:

  • 23

  • about 1000

  • 46

  • about 8 million

Explicación

Pregunta 71 de 100

1

Independent assortment of chromosomes is a result of _____.

Selecciona una de las siguientes respuestas posibles:

  • the random combinations of eggs and sperm during fertilization

  • the random distribution of the sister chromatids to the two daughter cells during anaphase II

  • the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

  • the diverse combination of alleles that may be found within any given chromosome

Explicación

Pregunta 72 de 100

1

When homologous chromosomes cross over, what occurs?

Selecciona una de las siguientes respuestas posibles:

  • Maternal alleles are "corrected" to be like paternal alleles and vice versa.

  • Two chromatids get tangled, resulting in one re-sequencing its DNA.

  • Two sister chromatids exchange identical pieces of DNA.

  • Corresponding segments of non-sister chromatids are exchanged.

Explicación

Pregunta 73 de 100

1

How is natural selection related to sexual reproduction as opposed to asexual reproduction?

Selecciona una de las siguientes respuestas posibles:

  • Sexual reproduction results in the greatest number of new mutations.

  • Sexual reproduction allows the greatest number of offspring to be produced.

  • Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction.

  • Sexual reproduction utilizes far less energy than asexual reproduction.

Explicación

Pregunta 74 de 100

1

The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. Diversity in this species may be generated by mutations and _____.

Selecciona una de las siguientes respuestas posibles:

  • independent assortment

  • crossing over

  • nothing else

  • crossing over and independent assortment

Explicación

Pregunta 75 de 100

1

The fastest way for organisms to adapt to a changing environment involves _____.

Selecciona una de las siguientes respuestas posibles:

  • sexual reproduction

  • asexual reproduction

  • mutation

Explicación

Pregunta 76 de 100

1

Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early twentieth century?

Selecciona una de las siguientes respuestas posibles:

  • Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis.

  • Individuals inherit particular chromosomes attached to genes.

  • No more than a single pair of chromosomes can be found in a healthy normal cell.

  • Natural selection acts on certain chromosome arrays rather than on genes.

Explicación

Pregunta 77 de 100

1

Males are more often affected by sex-linked traits than females because _____.

Selecciona una de las siguientes respuestas posibles:

  • X chromosomes in males generally have more mutations than X chromosomes in females

  • male hormones such as testosterone often alter the effects of mutations on the X chromosome

  • males are hemizygous for the X chromosome

  • female hormones such as estrogen often compensate for the effects of mutations on the X chromosome

Explicación

Pregunta 78 de 100

1

SRY is best described as _____.

Selecciona una de las siguientes respuestas posibles:

  • an autosomal gene that is required for the expression of genes on the Y chromosome

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

  • a gene present on the X chromosome that triggers female development

  • an autosomal gene that is required for the expression of genes on the X chromosome

Explicación

Pregunta 79 de 100

1

In humans, clear gender differentiation occurs, not at fertilization, but after the second month of gestation. What is the first event of this differentiation?

Selecciona una de las siguientes respuestas posibles:

  • formation of testosterone in male embryos

  • activation of SRY in male embryos and masculinization of the gonads

  • activation of SRY in females and feminization of the gonads

  • formation of estrogens in female embryos

Explicación

Pregunta 80 de 100

1

All female mammals have one active X chromosome per cell instead of two. What causes this?

Selecciona una de las siguientes respuestas posibles:

  • attachment of methyl (CH3) groups to the X chromosome that will remain active

  • activation of the BARR gene on one X chromosome, which then becomes inactive

  • inactivation of the XIST gene on the X chromosome derived from the male parent

  • activation of the XIST gene on the X chromosome that will become the Barr body

Explicación

Pregunta 81 de 100

1

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?

Selecciona una de las siguientes respuestas posibles:

  • incomplete dominant, sex-linked

  • recessive, sex-linked

  • recessive, autosomal

  • dominant, sex-linked

Explicación

Pregunta 82 de 100

1

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 couple's first son will be color blind?

Selecciona una de las siguientes respuestas posibles:

  • 3/4

  • 1/2

  • 1/4

  • 2/3

Explicación

Pregunta 83 de 100

1

A man who carries an allele of an X-linked gene will pass it on to _____.

Selecciona una de las siguientes respuestas posibles:

  • all of his sons

  • all of his daughters

  • half of his daughters

  • all of his children

Explicación

Pregunta 84 de 100

1

Which of the following statements is true of linkage?

Selecciona una de las siguientes respuestas posibles:

  • The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

  • All of the traits that Mendel studied–seed color, pod shape, flower color, and others–are due to genes linked on the same chromosome.

  • Linked genes are found on different chromosomes.

  • The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.

Explicación

Pregunta 85 de 100

1

Recombination between linked genes comes about for what reason?

Selecciona una de las siguientes respuestas posibles:

  • Linked genes travel together at anaphase.

  • Independent assortment sometimes fails.

  • Nonrecombinant chromosomes break and then rejoin with one another.

  • Crossovers between these genes result in chromosomal exchange.

Explicación

Pregunta 86 de 100

1

What is an adaptive advantage of recombination between linked genes?

Selecciona una de las siguientes respuestas posibles:

  • New allele combinations are acted upon by natural selection.

  • Recombination must occur or genes will not assort independently.

  • Recombination is required for independent assortment.

  • The forces on the cell during meiosis II results in recombination.

Explicación

Pregunta 87 de 100

1

What is the reason that closely linked genes are typically inherited together?

Selecciona una de las siguientes respuestas posibles:

  • They are located close together on the same chromosome.

  • The number of genes in a cell is greater than the number of chromosomes.

  • Genes align that way during metaphase I of meiosis.

  • Alleles are paired together during meiosis.

Explicación

Pregunta 88 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • duplication

  • deletion

  • inversion

  • translocation

Explicación

Pregunta 89 de 100

1

A nonreciprocal crossover causes which of the following products?

Selecciona una de las siguientes respuestas posibles:

  • nondisjunction

  • deletion only

  • deletion and duplication

  • duplication only

Explicación

Pregunta 90 de 100

1

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

Selecciona una de las siguientes respuestas posibles:

  • an increase in nondisjunction

  • failure of the cancer cells to multiply

  • expression of inappropriate gene products

  • a decrease in mitotic frequency

Explicación

Pregunta 91 de 100

1

What is a syndrome?

Selecciona una de las siguientes respuestas posibles:

  • a trait that leads to cancer at some stage in life

  • a specific characteristic that appears in conjunction with one specific aneuploidy

  • a characteristic facial appearance

  • a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation

Explicación

Pregunta 92 de 100

1

Which of the following is known as a Philadelphia chromosome?

Selecciona una de las siguientes respuestas posibles:

  • a human chromosome 9 that is found only in one type of cancer

  • a human chromosome 22 that has had a specific translocation

  • a chromosome found only in mitochondria

  • an animal chromosome found primarily in the mid-Atlantic area of the United States

Explicación

Pregunta 93 de 100

1

Which of the following is an example of monosomy?

Selecciona una de las siguientes respuestas posibles:

  • Klinefelter's syndrome

  • Turner's syndrome

  • trisomy X

  • Down syndrome

Explicación

Pregunta 94 de 100

1

Genomic imprinting is generally due to the addition of methyl (CH3) groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following must be true?

Selecciona una de las siguientes respuestas posibles:

  • The imprints are transmitted only to gamete-producing cells.

  • Genes required for early development stages must not be imprinted.

  • Methylation must be reversible in ovarian and testicular cells.

  • Methylation of this kind must occur more in males than in females.

Explicación

Pregunta 95 de 100

1

Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect _____.

Selecciona una de las siguientes respuestas posibles:

  • DNA synthesis in cells of the immune system

  • the storage of urine in the urinary bladder

  • generation of ATP in muscle cells

  • the movement of oxygen into erythrocytes

Explicación

Pregunta 96 de 100

1

Nothing in biology makes sense except in the light of evolution.

Selecciona una de las siguientes respuestas posibles:

  • True

  • False

Explicación

Pregunta 97 de 100

1

Intelligent design is a major driving force for biological understanding.

Selecciona una de las siguientes respuestas posibles:

  • True

  • False

Explicación

Pregunta 98 de 100

1

Eukaryotic Cells lack a nucleus.

Selecciona una de las siguientes respuestas posibles:

  • True

  • False

Explicación

Pregunta 99 de 100

1

ALL cells in eukaryotic organisms express the same genes.

Selecciona una de las siguientes respuestas posibles:

  • True

  • False

Explicación

Pregunta 100 de 100

1

The DNA sequence is more similar with common biological ancestors.

Selecciona una de las siguientes respuestas posibles:

  • True

  • False

Explicación

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