bio chapters 12 & 13

A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of the couple's daughters might be expected to be color-blind dwarfs? a)all b)none c)half d)one out of four e)three out of four

B

Aneuploid conditions are best described by which of the following? a)A monosomy is more frequent than a trisomy. b)Monosomy X is the only known viable human monosomy. c)Of all human aneuploidies, only Down syndrome is associated with mental retardation. d)An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

B

Which enzyme catalyzes the elongation of a DNA strand in the 5'>3' direction? a)primase b)DNA ligase c)DNA polymerase III d)topoisomerase e)helicase

C

A frequency of recombination of 50% indicates what? a)The two genes are likely to be located on different chromosomes. b)All of the offspring have combinations of traits that match one of the two parents. c)The genes are located on sex chromosomes. d)Independent assortment is hindered.

A

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)8% b)16% c)31% d)42%

A

During DNA replication, which of the following enzymes separates the DNA strands during replication? a)helicase b)DNA polymerase III c)ligase d)DNA polymerase I e)primase

A

Linkage is best described by which of the following statements? a)The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. b)The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%. c)All of the traits that Mendel studied-seed color, pod shape, flower color, and others-are due to genes linked on the same chromosome. d)Linked genes are found on different chromosomes.

A

The leading and the lagging strands of DNA formed during DNA replication 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

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? a)DNA polymerase can join new nucleotides only to the 3' end of a preexisting strand. b)Helicases and single-strand binding proteins work at the 5' end. c)The origins of replication occur only at the 5' end. d)Only a fraction of an individual's offspring may survive.

A

What is the function of topoisomerase? a)relieving strain in the DNA ahead of the replication fork b)elongating new DNA at a replication fork by adding nucleotides to the existing chain c)adding methyl groups to bases of DNA d)unwinding of the double helix e)stabilizing single-stranded DNA at the replication fork

A

What is the reason that closely linked genes are typically inherited together? a)The likelihood of a crossover event between these two genes is low. b)The number of genes in a cell is greater than the number of chromosomes. c)Chromosomes are unbreakable. d)Alleles are paired together during meiosis. e)Genes align that way during metaphase I of meiosis.

A

Which choice best explains a testcross with F1 dihybrid flies where more parental-type offspring than recombinant-type offspring are produced? a)The two genes are closely linked on the same chromosome. b)The two genes are linked but on different chromosomes. c)Recombination did not occur in the cell during meiosis. d)Both of the characters are controlled by more than one gene.

A

Which of the following human aneuploidies, generally has the most severe impact on the health of the individual? a)47,+21 b)47,XXY c)47,XXX d)47,XYY e)45.X

A

Which of the following statements accurately describes why Taq polymerase is used in PCR? a)It is heat stable and can withstand the heating step of PCR. b)Only minute amounts are needed for each cycle of PCR. c)It binds more readily than other polymerases to the primers. d)It has regions that are complementary to the primers. e)It is heat stable, and it binds more readily than other polymerases to the primers.

A

What is meant by the description "antiparallel" regarding the two strands of nucleic acids that make up DNA? a)The twisting nature of DNA creates nonparallel strands. b)The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. c)Base pairings create unequal spacing between the two DNA strands. d)One strand contains only purines and the other contains only pyrimidines.

B

Which of the following statements describes one difference between DNA replication in prokaryotes and DNA replication in eukaryotes? a)Prokaryotic chromosomes have 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

Which of the following values is equivalent to one map unit? a)the physical distance between two linked genes b)1% frequency of recombination between two genes c)1 nanometer of distance between two genes d)the distance between a pair of homologous chromosomes e)the recombination frequency between two genes assorting independently

B

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. In a cross of female with cinnabar eyes with wild-type male the percentage of the F1 males with cinnabar eyes would be expected to be what? a)0% b)25% c)50% d)75% e)100%

E

In which order do the necessary enzymes act to repair a thymine dimer by nucleotide excision repair? a)nuclease, DNA polymerase, RNA primase b)helicase, DNA polymerase, DNA ligase c)DNA ligase, nuclease, helicase d)DNA polymerase, RNA polymerase, DNA ligase e)nuclease, DNA polymerase, DNA ligase

E

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)Neither of the two daughter cells would be radioactive. c)All four bases of the DNA would be radioactive. d)Radioactive thymine would pair with nonradioactive guanine. e)DNA in both daughter cells would be radioactive.

E

Which of the following enzymes synthesizes short segments of RNA? a)helicase b)DNA polymerase III c)ligase d)DNA polymerase e)primase

E

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)The likelihood of a crossover event between these two genes is low. b)The number of genes in a cell is greater than the number of chromosomes. c)Chromosomes are unbreakable. d)Alleles are paired together during meiosis. e)Genes align that way during metaphase I of meiosis.

C

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 joins Okazaki fragments together. d)It unwinds the parental double helix. e)It stabilizes the unwound parental DNA.

C

Which choice best explains a syndrome? a)a characteristic facial appearance b)a group of traits, all of which must be present if an aneuploidy is to be diagnosed c)a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation d)a characteristic trait usually given the discoverer's name e)a characteristic that only appears in conjunction with one specific aneuploidy

C

Which of the following modifications is most likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis? a)altering the nucleotide sequence of the DNA fragment without adding or removing nucleotides b)radioactively labeling the cytosine bases within the DNA fragment c)increasing the length of the DNA fragment d)leaving the length of the DNA fragment the same

C

Which of the following statements correctly describes chromatin? a)Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA. b)Both heterochromatin and euchromatin are found in the cytoplasm. c)Heterochromatin is highly condensed, whereas euchromatin is less compact. d)Euchromatin is not transcribed, whereas heterochromatin is transcribed.

C

During DNA replication, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? a)helicase b)DNA polymerase III c)ligase d)DNA polymerase I e)primase

D

In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. Which of the following investigators was (were) responsible for this discovery? a)Frederick Griffith b)Alfred Hershey and Martha Chase c)Oswald Avery d)Erwin Chargaff e)Matthew Meselson and Franklin Stahl

D

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called? a)deletion b)transversion c)inversion d)translocation e)duplication

D

Sex-linked traits affect males more often than females because a)male hormones such as testosterone often alter the effects of mutations on the X chromosome. b)female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. c)X chromosomes in males generally have more mutations than X chromosomes in females. d)males are hemizygous for the X chromosome. e)mutations on the Y chromosome often worsen the effects of X-linked mutations.

D

What causes the extra chromosome 21 in an individual with Down syndrome? a)nondisjunction in the mother only b)nondisjunction in the father only c)duplication of the chromosome d)nondisjunction or translocation in either parent

D

Which of the following help(s) to hold the DNA strands apart while they are being replicated? a)primase b)ligase c)DNA polymerase d)single-strand binding proteins e)nuclease

D

Which of the following statements best describes the eukaryotic chromosome? a)It is composed of DNA alone. b)The nucleosome is its most basic functional subunit. c)The number of genes on each chromosome is different in different cell types of an organism. d)It consists of a single linear molecule of double-stranded DNA plus proteins.

D

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, whereas protein does not. c)DNA contains nitrogen, whereas protein does not. d)DNA contains purines, whereas protein includes pyrimidines. e)RNA includes ribose, whereas DNA includes deoxyribose sugars.

B

The inversion of a human chromosome often results in no visible phenotypic effect on the individual. What else may occur? a)There may be deletions later in life. b)Some abnormal gametes may be formed. c)There is an increased frequency of mutation. d)The individual is more likely to get cancer.

B

Thomas Hunt Morgan crossed red-eyed F1 generation flies to each other, the F2 generation included red- and white-eyed flies. Somehow, all the white-eyed flies were male. What is the explanation for this result? a)The gene involved is on the Y chromosome. b)The gene involved is on the X chromosome. c)The gene involved is on an autosome, but only in males. d)Eye color in flies is a multifactorial trait.

B

What did Griffith observe in his transformation experiments? a)Mutant mice were resistant to bacterial infections. b)Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. c)Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. d)Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

B

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. What is the probable cause of the child's condition? a)The woman inherited this tendency from her parents. b)One member of the couple carried a translocation. c)One member of the couple underwent nondisjunction in somatic cell production. d)One member of the couple underwent nondisjunction in gamete production. e)The mother had a chromosomal duplication.

D

A new DNA strand elongates only in the 5' to 3' direction because a)DNA polymerase begins adding nucleotides at the 5' end of the template. b)Okazaki fragments prevent elongation in the 3' to 5' direction. c)replication must progress toward the replication fork. d)DNA polymerase can only add nucleotides to the free 3' end.

D