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| 245216135 | Chromosomes and genes share all of the following characteristics except that | they both pair up with their homologues during prophase of mitosis | |
| 245216136 | The improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics because | it allowed biologists to study meiosis and mitosis, revealing the parallels between the behaviors of genes and chromosomes | |
| 245216137 | When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? | The involved gene was on the X chromosome. | |
| 245216138 | Which of the following statements is (are) true? | Only B and C are correct. | |
| 245216139 | How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? | The two genes are linked. | |
| 245216140 | New combinations of linked genes are due to which of the following? | crossing over | |
| 245216141 | What does a frequency of recombination of 50% indicate? | The two genes likely are located on different chromosomes. | |
| 245216142 | The reason that linked genes are inherited together is that | they are located on the same chromosome. | |
| 245216143 | What is the mechanism for the production of genetic recombinants? | crossing over and independent assortment | |
| 245216144 | There is good evidence for linkage when | genes do not segregate independently during meiosis. | |
| 245216145 | Which of the following is true regarding linkage maps? They | are a genetic map based on recombination frequencies. | |
| 245216146 | The frequency of crossing over between any two linked genes is | proportional to the distance between them | |
| 245216147 | Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila by showing that | Drosophila genes cluster into four distinct groups of linked genes | |
| 245216148 | Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome because | the frequency of crossing over varies along the length of the chromosome | |
| 245216149 | A map of a chromosome that includes the positions of genes relative to visible chromosomal features, such as stained bands, is called a | cytogenetic map. | |
| 245216150 | Males are more often affected by sex-linked traits than females because | males are hemizygous for the X chromosome | |
| 245216151 | What is the chromosomal system for determining sex in mammals? | X-Y | |
| 245216152 | What is the chromosomal system for sex determination in grasshoppers and certain other insects? | X-0 | |
| 245216153 | What is the chromosomal system for sex determination in birds? | Z-W | |
| 245216154 | What is the chromosomal system of sex determination in most species of ants and bees? | haploid-diploid | |
| 245216155 | SRY is | a gene present on the Y chromosome that triggers male development | |
| 245216156 | 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? | tortoiseshell female; black male | |
| 245216157 | Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? | XCXc and XCY | |
| 245216158 | In the following list, which term is least related to the others? | autosome | |
| 245216159 | Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? | 100% | |
| 245216160 | Most calico cats are female because | a male inherits only one of the two X-linked genes controlling hair color | |
| 245216161 | 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 a son of this couple will be color-blind? | 1/2 | |
| 245216162 | In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A lethal recessive allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female? | 2:1 male to female | |
| 245216163 | A man who carries an X-linked allele will pass it on to | all of his daughters. | |
| 245216164 | An achondroplastic male dwarf with normal vision marries a color-blind woman of normal height. The man's father was six-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 their daughters might be expected to be color-blind dwarfs? | none | |
| 245216165 | An achondroplastic male dwarf with normal vision marries a color-blind woman of normal height. The man's father was six-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 their sons would be color-blind and of normal height? | half | |
| 245216166 | An achondroplastic male dwarf with normal vision marries a color-blind woman of normal height. The man's father was six-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. They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes? | 1.00 | |
| 245216167 | Male calico cats could be the result of | nondisjunction, leading to the male calico having two X chromosomes | |
| 245216168 | A Barr body is normally found in the nucleus of which kind of human cell? | somatic cells of a female only | |
| 245216169 | Which of these syndromes afflicts mostly males? | Duchenne muscular dystrophy | |
| 245216170 | If a human interphase nucleus of a person contains three Barr bodies, it can be assumed that the person | has four X chromosomes. | |
| 245216171 | If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis? | One gamete will be n + 1, one will be n - 1, and two will be n. | |
| 245216172 | If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n)? | n + 1; n + 1; n - 1; n - 1 | |
| 245216173 | A cell that has 2n + 1 chromosomes is | both A and C | |
| 245216174 | If a chromosome lacks certain genes, what has most likely occurred? | a deletion | |
| 245216175 | One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. This is called a (an) | translocation | |
| 245216176 | In the following list, which term is least related to the others? | triploid | |
| 245216177 | A nonreciprocal crossover causes which of the following products? | A and B | |
| 245216178 | One possible result of chromosomal breakage can be that a fragment reattaches to the original chromosome in a reverse orientation. This is called | inversion | |
| 245216179 | A human individual is phenotypically female, but her interphase somatic nuclei do not show the presence of Barr bodies. Which of the following statements concerning her is probably true? | She has Turner syndrome. | |
| 245216180 | In humans, male-pattern baldness is controlled by a gene that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald? | 75% | |
| 245216181 | Of the following human trisomies, the one that generally has the most severe impact on the health of the individual is | trisomy 21 | |
| 245216182 | What do all human males inherit from their mother? | A and B only | |
| 245216183 | Which of the following statements is true regarding genomic imprinting? | It explains cases in which the gender of the parent from whom an allele is inherited affects the expression of that allele | |
| 245216184 | Which of the following statements about mitochondria is false? | Like nuclear genes, mitochondrial genes usually follow Mendelian patterns of inheritance | |
| 245216185 | You conduct a dihybrid cross and then testcross the F1 generation. A ________ ratio would make you suspect that the genes are linked. | 7:7:1:1 | |
| 245216186 | The recombination frequency between gene A and gene B is 8.4%, the recombination frequency between gene A and gene C is 6.8%, and the recombination frequency between gene B and gene C is 15.2%. Which is the correct arrangement of these genes? | CAB | |
| 245216187 | Hypophosphatemia (vitamin D-resistant rickets) is inherited as a X-linked dominant disorder. An unaffected woman mates with a male with hypophosphatemia. What is the expected phenotypic ratio of their offspring? | 1 daughter with hypophosphatemia:1 normal son | |
| 245216188 | The sex chromosome complements of both normal human and normal MendAlien males is | XY | |
| 245216189 | Mutant tetraploid plants | are unable to breed with a diploid plant. | |
| 245216190 | A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will be a hemophiliac? That a son will be a hemophiliac? If the couple has four sons, what is the probability that all four will be born with hemophilia? | 0; 1/2, 1/16 | |
| 245216191 | Pseudohypertrophic muscular dystrophy is an inherited disorder that causes gradual deterioration of the muscles. It is seen almost exclusively in boys born to apparently normal parents and usually results in death in the early teens. Is this disorder caused by a dominant or a recessive allele? Is its inheritance sex-linked or autosomal? How do you know? Explain why this disorder is almost never seen in girls | Recessive. If the disorder were dominant, it would affect at least one parent of a child born with the disorder. The disorder's inheritance is sex-linked because it is seen almost only in boys. For a girl to have the disorder, she would have to inherit the recessive alleles from both parents. This would be very rare since males with the recessive allele on their X chromosome die in their early teens. | |
| 245216192 | Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color-blind. What is the probability that they will have a color-blind daughter? What is the probability that their first son will be color-blind? | 1/4 for each daughter (1/2 chance that child will be female × 1/2 chance of a homozygous recessive genotype); 1/2 for first son. | |
| 245216193 | A wild-type fruit fly (heterozygous for gray body color and normal wings) is mated with a black fly with vestigial wings. The offspring have the following phenotypic distribution: wild type, 778; black-vestigial, 785; black-normal, 158; gray-vestigial, 162. What is the recombination frequency between these genes for body color and wing size? | 17% | |
| 245216194 | In another cross, a wild-type fruit fly (heterozygous for gray body color and red eyes) is mated with a black fruit fly with purple eyes. The offspring are as follows: wild type, 721; black-purple, 751; gray-purple, 49; black-red, 45. What is the recombination frequency between these genes for body color and eye color? Using information from problem 4, what fruit flies (genotypes and phenotypes) would you mate to determine the sequence of the body-color, wing-size, and eye-color genes on the chromosome? | 6%. Wild type (heterozygous for normal wings and red eyes) × recessive homozygote with vestigial wings and purple eyes | |
| 245216195 | What pattern of inheritance would lead a geneticist to suspect that an inherited disorder of cell metabolism is due to a defective mitochondrial gene? | The disorder would always be inherited from the mother | |
| 245216196 | Women born with an extra X chromosome (XXX) are healthy and phenotypically indistinguishable from normal XX women. What is a likely explanation for this finding? How could you test this explanation? | The inactivation of two X chromosomes in XXX women would leave them with one genetically active X, as in women with the normal number of chromosomes. Microscopy should reveal two Barr bodies in XXX women. | |
| 245216197 | Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B, 8 map units; A-C, 28 map units; A-D, 25 map units; B-C, 20 map units; B-D, 33 map units. | D-A-B-C | |
| 245216198 | Assume that genes A and B are linked and are 50 map units apart. An animal heterozygous at both loci is crossed with one that is homozygous recessive at both loci. What percentage of the offspring will show phenotypes resulting from crossovers? If you did not know that genes A and B were linked, how would you interpret the results of this cross? | 50% of the offspring would show phenotypes that resulted from crossovers. These results would be the same as those from a cross where A and B were not linked. Further crosses involving other genes on the same chromosome would reveal the linkage and map distances. | |
| 245216199 | Fifty percent of the offspring would show phenotypes that resulted from crossovers. These results would be the same as those from a cross where A and B were not linked. Further crosses involving other genes on the same chromosome would reveal the linkage and map distances. | Between T and A, 12%; between A and S, 5% |
