Lester Bio Quiz Part 3

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest about the trait?

A. that the parents were true-breeding for contrasting traits

B. that a blending of traits has occurred

C. that the trait shows incomplete dominance

D. that the parents were both heterozygous for a single trait

D. that the parents were both heterozygous for a single trait

Which of the following statements correctly describes a monohybrid cross?

A. A monohybrid cross is performed for one generation.

B. A monohybrid cross involves a single parent.

C. A monohybrid cross involves organisms that are heterozygous for one character.

D. A monohybrid cross produces a single offspring.

C. A monohybrid cross involves organisms that are heterozygous for one character.

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

A. 8

B. 4

C. 16

D. 64

A. 8

Which of the following statements correctly describes an example of epistasis?

A. In Drosophila (fruit flies), white eyes can be due to a combination of multiple genes.

B. Recessive genotypes for each of two genes (aabb) result in an albino corn snake.

C. In cacti, there are several genes for the type of spines.

D. In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.

D. In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.

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

A. Recessive genes occur more frequently in the F1 generation than do dominant ones.

B. Traits are inherited in discrete units and are not the results of the "blending" of traits.

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

D. There is considerable genetic variation in garden peas.

B. Traits are inherited in discrete units and are not the results of the "blending" of traits.

Achondroplasia, a form of dwarfism in humans, is caused by a dominant allele. What is the probability of a heterozygous dwarf man and a normal, homozygous woman having a child who is a heterozygous dwarf?

A. 50%

B. 0%

C. 100%

D. 25%

A. 50%

Which of the following statements correctly describes a dihybrid cross?

A. A dihybrid cross involves two parents.

B. A dihybrid cross produces two offspring.

C. A dihybrid cross results in a 3:1 phenotype ratio in the F2 offspring.

D. A dihybrid cross involves organisms that are heterozygous for two characters.

D. A dihybrid cross involves organisms that are heterozygous for two characters.

Phenylketonuria (PKU) is a disease in humans that results from the abnormal metabolism of the amino acid phenylalanine. If untreated, it can lead to severe brain damage in infants. Two normal parents have a child who has PKU. What can you determine about the inheritance of the PKU allele from this information?

A. It is pleiotropic.

B. It is dominant.

C. It is epistatic.

D. It is recessive.

D. It is recessive.

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

A. pleiotropy

B. epistasis

C. incomplete dominance

D. multiple alleles

A. pleiotropy

Skin color in humans has a wide variety of phenotypes. The expression of this trait is caused by more than two genes. What type of inheritance pattern is responsible for this expression?

A. codominance

B. complete dominance

C. incomplete dominance

D. polygenic inheritance

D. polygenic inheritance

Which of the following statements correctly describes aneuploid conditions?

A. A monosomy is more frequent than a trisomy.

B. An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

C. Of all human aneuploidies, only Down syndrome is associated with developmental delays or subnormal intelligence.

D. Monosomy X is the only known viable human monosomy.

D. Monosomy X is the only known viable human monosomy.

What is a syndrome?

A. a group of traits, all of which must be present if an aneuploidy is to be diagnosed

B. a characteristic facial appearance

C. a characteristic trait usually given the discoverer's name

D. a group of traits typically found in conjunction with a particular chromosomal alteration or gene mutation

D. a group of traits typically found in conjunction with a particular chromosomal alteration or gene mutation

Red-green color blindness is a sex-linked recessive trait in humans. The normal, dominant allele is symbolized with XN, and the recessive allele is symbolized with Xn. Two people with normal color vision have a color-blind son. What are the genotypes of these parents?

A. X^NX^N and X^NY

B. X^NX^N and X^nY

C. X^nX^n and X^NY

D. X^NX^n and X^nY

E. X^NX^n and X^NY

E. X^NX^n and X^NY

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?

A. One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

B. Half of the gametes descended from cell X will be n + 1, and half will be n - 1.

C. All the gametes descended from cell X will be diploid.

D. All of the gametes will have the normal number of chromosomes.

A. One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

One map unit is equivalent to which of the following values?

A. 1% frequency of recombination between two genes

B. 1 nanometer of distance between two genes

C. The physical distance between two linked genes

D. the distance between a pair of homologous chromosomes

A. 1% frequency of recombination between two genes

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

A. X chromosomes in males generally have more mutations than X chromosomes in females.

B. sex-linked traits are located on autosomes that affect males more severely than females.

C. the presence of a Y chromosome often worsens D. the effects of X-linked mutations.

E. males are hemizygous for the X chromosome.

E. males are hemizygous for the X chromosome.

Which of the following statements best describes the SRY gene?

A. It is an autosomal gene that is required for the expression of genes on the Y chromosome.

B. It is a gene present on the X chromosome that triggers female development.

C. It is a gene region present on the Y chromosome that triggers male development.

D. It is an autosomal gene that is required for the expression of genes on the X chromosome.

C. It is a gene region present on the Y chromosome that triggers male development.

Which of the following statements correctly describes gene linkage?

A. Linked genes always assort independently.

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

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

D. Linked genes are found on different chromosomes.

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

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

A. orange females; orange males

B. black females; orange males

C. tortoiseshell females; black males

D. tortoiseshell females; tortoiseshell males

C. tortoiseshell females; black males

What is the source of the extra chromosome 21 in an individual with Down syndrome?

A. nondisjunction in the mother-only

B. nondisjunction in either parent

C. duplication of the chromosome

D. nondisjunction in the father only

B. nondisjunction in either parent

Which of the following statements correctly describes gene linkage?

A. Linked genes always assort independently.

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

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

D. Linked genes are found on different chromosomes.

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

Which of the following events causes recombination between linked genes to occur?

A. Independent assortment of the genes.

B. Nonrecombinant chromosomes break and then re-join with one another.

C. Crossovers between the genes results in chromosomal exchange.

D. Mutation that causes one homolog to be different from the other homolog.

C. Crossovers between the genes results in chromosomal exchange.

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

A. formation of testosterone in male embryos

B. activation of the SRY gene in male embryos and development of testes

C. anatomical differentiation of a penis in male embryos

D. formation of estrogens in female embryos

B. activation of the SRY gene in male embryos and development of testes

Which of the following statements describes the chromosome theory of inheritance as expressed in the early twentieth century?

A. Individuals inherit particular chromosomes attached to genes.

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

C. Homologous chromosomes give rise to some genes and crossover chromosomes to other genes.

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

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

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

A. orange females; orange males

B. black females; orange males

C. tortoiseshell females; black males

D. tortoiseshell females; tortoiseshell males

C. tortoiseshell females; black males

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?

A. One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

B. Half of the gametes descended from cell X will be n + 1, and half will be n - 1.

C. All the gametes descended from cell X will be diploid.

D. All of the gametes will have the normal number of chromosomes.

A. One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

What is the result of the activation of the XIST gene in mammals?

A. the expression of sex-linked traits in males

B. the inactivation of one of the X chromosomes, which then becomes a Barr body in females

C. the activation of genes on both X chromosomes in females

D. activation of the SRY gene that results in the development of male sexual characteristics

B. the inactivation of one of the X chromosomes, which then becomes a Barr body in females

One map unit is equivalent to which of the following values?

A. 1% frequency of recombination between two genes

B. 1 nanometer of distance between two genes

C. the physical distance between two linked genes

D. the distance between a pair of homologous chromosomes

A. 1% frequency of recombination between two genes

Which of the following statements best describes the SRY gene?

A. It is an autosomal gene that is required for the expression of genes on the Y chromosome.

B. It is a gene present on the X chromosome that triggers female development.

C. It is a gene region present on the Y chromosome that triggers male development.

D. It is an autosomal gene that is required for the expression of genes on the X chromosome.

C. It is a gene region present on the Y chromosome that triggers male development.

What does a frequency of recombination of 50% between two genes indicate?

A. The two genes are likely to be located on different chromosomes.

B. The genes are located on sex chromosomes.

C. Independent assortment of the two genes will not occur.

D. All of the offspring have combinations of traits that match one of the two parents.

A. The two genes are likely to be located on different chromosomes.

In trying to determine whether DNA or protein was the genetic material, Hershey and Chase made use of which of the following facts about these two types of molecules?

A. DNA contains sulfur, whereas protein does not.

B. DNA contains nitrogen, whereas protein does not.

C. DNA contains phosphorus, whereas protein does not.

D. DNA contains purines, whereas protein includes pyrimidines.

C. DNA contains phosphorus, whereas protein does not.

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

A. One of the daughter cells, but not the other, would have radioactive DNA.

B. All four bases of the DNA would be radioactive.

C. Neither of the two daughter cells would be radioactive.

D. DNA in both daughter cells would be radioactive.

D. DNA in both daughter cells would be radioactive.

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

A. 31%

B. 8%

C. 16%

D. 42%

B. 8%

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

A. DNA polymerase

B. single-strand binding proteins

C. primase

D. ligase

B. single-strand binding proteins

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

A. A = G and C = T

B. A + C = G + T

C. A = C

D. G + C = T + A

B. A + C = G + T

In his transformation experiments, which of the following results did Griffith observe?

A. Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

B. Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

C. Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.

D. Mutant mice were resistant to bacterial infections.

A. Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

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

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

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

C. Okazaki fragments prevent elongation in the 3' to 5' direction.

D. Replication must progress toward the replication fork.

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

Which of the following statements correctly describes one difference between heterochromatin and euchromatin?

A. Euchromatin is not transcribed, whereas heterochromatin is transcribed.

B. Heterochromatin is found in the cytoplasm while euchromatin is found in the nucleus.

C. Heterochromatin is highly condensed, whereas euchromatin is less compact.

D. Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.

C. Heterochromatin is highly condensed, whereas euchromatin is less compact.

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

A. to degrade damaged DNA molecules

B. to unwind the DNA helix during replication

C. to seal together the broken ends of DNA strands

D. to add nucleotides to the 3' end of a growing DNA strand

D. to add nucleotides to the 3' end of a growing DNA strand

Which of the following statements best describes the eukaryotic chromosome?

A. The number of genes on each chromosome is different in different cell types of an organism.

B. It is composed of DNA alone.

C. It consists of a single linear molecule of double-stranded DNA plus proteins.

D. The nucleosome is its most basic functional subunit.

C. It consists of a single linear molecule of double-stranded DNA plus proteins.

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

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

B. DNA has a double helical structure.

C. DNA base composition does not vary between species.

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

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

What is the function of topoisomerase?

A. relieving strain in the DNA ahead of the replication fork

B. adding methyl groups to bases of DNA

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

D. unwinding of the double helix

A. relieving strain in the DNA ahead of the replication fork

Which of the following characteristics of the structure of DNA was determined directly from X-ray diffraction photographs of crystallized DNA?

A. the frequency of A versus T nucleotides

B. the sequence of nucleotides

C. the double helical structure

D. the length of a given DNA molecule

C. the double helical structure

How does a bacterial cell protect its own DNA from restriction enzymes?

A. by forming "sticky ends" of bacterial DNA to prevent the enzyme from attaching

B. by adding methyl groups to adenines and cytosines

C. by adding histones to protect the double-stranded DNA

D. by using DNA ligase to seal the bacterial DNA into a closed circle

B. by adding methyl groups to adenines and cytosines

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

A. DNA ligase

B. primase

C. topoisomerase

D. DNA polymerase III

D. DNA polymerase III

Why do histones bind tightly to DNA?

A. Histones are covalently linked to the DNA.

B. Histones are positively charged, and DNA is negatively charged.

C. Histones are negatively charged, and DNA is positively charged.

D. Both histones and DNA are strongly hydrophobic.

B. Histones are positively charged, and DNA is negatively charged.

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

A. The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and

B. the lagging strand is synthesized by adding nucleotides to the 5' end.

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

C. The leading strand is synthesized a

D. 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.

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

A. complementary pairing of bases

B. the sequence of bases

C. different five-carbon sugars

D. phosphate-sugar backbones

B. the sequence of bases

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

A. It synthesizes RNA nucleotides to make a primer.

B. It catalyzes the lengthening of telomeres.

C. It unwinds the parental double helix.

D. It joins Okazaki fragments together.

D. It joins Okazaki fragments together.

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

A. Transformation is the infection of cells by a phage DNA molecule.

B. Transformation is the creation of a strand of DNA from an RNA molecule.

C. Transformation is the creation of a strand of RNA from a DNA molecule.

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

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