Chapter 15

23:Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%; B-C: 14%; A-C: 5%; B-D: 2%; A-D: 21%; C-D: 16%. Based on this information, which sequence of genes is correct? (Concept

ACBD

Which of the following results of Thomas Hunt Morgan's experiment with white-eyed mutant flies was unexpected in light of mendelian genetics?

Among the F, progeny, only males had white eyes. All of the females had red eyes. The mutant allele (white eyes) was recessive

Why did Morgan choose Drosophilia for his genetics experiment?

Both the second and fourth answers

40:What appears to be the mechanism for genomic imprinting? (Concept

DNA methylation that silences particular genes crossing over and DNA methylation that activates particular genes nondisjunction

13:Consider a woman who is a carrier of a recessive X-linked allele for hemophilia. Which of the following possibilities could explain the presence of the hemophilia allele in her genotype?(

Either her mother was a carrier or her father had hemophilia.

35:Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16? (Concept

Extra copies of the other chromosomes are probably fatal to the developing embryo.

A woman is red-green color-blind. What can we conclude, if anything, about her father?

He is red-green color-blind

14:In a certain fish, fin rays (supporting structures for the fins) can be either bony or soft in adult fish. Sex linkage in a fish is similar to that in humans. What evidence would most strongly support the idea that the ray locus is on the X chromosome? (Concept

Matings of soft ray males and bony ray females give different results from the matings of bony ray males and soft ray females.

32:__________ is usually less severe than __________, and __________ species have been observed in plants, fish, amphibians, and even mammals. (Concept

Polyploidy ... aneuploidy ... polyploid

16:X-linked genes differ from Y-linked genes in which of the following ways? (ConceptSons and daughters have equal probabilities in inheriting a recessive allele of an X- linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father.

Sons and daughters have equal probabilities in inheriting a recessive allele of an X- linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father

17:Which of the following best describes the function of the XIST gene in X chromosome inactivation?(Concept

The XIST gene on the X chromosome that will be inactivated is expressed to produce multiple RNA transcripts that bind to that chromosome and effectively cover it up, thereby generating a Barr body.

The chromosome theory of inheritance states that ___________________.

The first, second, and third are correct

19:In a particular species of mammal, black hair (B) is dominant to green hair (b), and red eyes (R) are dominant to white eyes (r). When a BbRr individual is mated with a bbrr individual, offspring are produced in a ratio of 5 black hair and red eyes:5 green hair and white eyes:1 black hair and white eyes:1 green hair and red eyes. The expected result would be equal numbers of these four phenotypes. Which of these explanations accounts for this ratio? (ConceptThe genes for hair color and eye color are linked.

The genes for hair color and eye color are linked.

Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20.Why is this disorder almost never seen in girls?

To express an X-linked recessive allele, a female must have two copies of the allele, one of which is contributed by the father.

Which of the following would result in genetic variation by the new way of new combination alleles?

independent alignment of homologous chromosomes during meiosis I, the exchange of alleles between homologous chromosomes during meiosis I and, random fertilization increasing the number of possible allele combinations in an individual

37:A person with two X chromosomes and one Y chromosome would appear to be __________.(Concept

male

28:Individuals with an extra X chromosome __________. (Concept 15.4)SHOW HINT are generally sterile

may have subnormal intelligence or be at risk for learning disabilities

26:Because the frequency of crossing over is not uniform along the length of a chromosome, __________. (Conceptmap units do not

necessarily correlate to physical distances along the chromosome

29:During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as __________. (Concept

nondisjunction

30:In Klinefelter syndrome, individuals are phenotypically male, but they have reduced sperm production and may have some breast development in adolescence. The cells of Klinefelter individuals have two X chromosomes and one Y (they are XXY instead of XY). This occurs because of what meiotic error? (Concept

nondisjunction

44:A person's remains are found, and officials are trying to identify them. A couple believes that the remains belong to their missing daughter. Because the remains have decayed considerably, mitochondrial DNA is being used to determine the person's identity. In order to determine if the remains belong to someone in this couple's family, whose mitochondrial DNA should be used for comparison? (Concept

one of the couples other children

25:A linkage map __________. (Concept

orders genes on a chromosome based on recombination frequencies

Wild type refers to _______________.

the most common phenotype thought to be found in the natural population

For an X-linked trait, it is the contribution of _____________________ that determines whether a son will display the trait.

the mother

18:If two genes are linked, __________. (Concept

they are on the same chromosome

21:You perform a testcross using F 1 dihybrid flies. If, in the resulting offspring, the percentages of parental and recombinant offspring are about the same, this would indicate that the two genes are __________. (Concept

unlinked

A woman is a carrier for red-green color blindness, a sex-linked trait. Her husband is normal (not color-blind) for this trait. What are the chances that their newborn daughter will be red-green color-blind?

0%

What is the probability that a human male will inherit an X-linked recessive allele from his father?

0%

34:The chromosomal abnormality in which a fragment of a chromosome breaks off and then reattaches to the original chromosome in the same place but in the reverse direction is called __________. (Concept

35:Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16? (Conceptinversion35:Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16? (Concept

12:Hemophilia is an X-linked disorder. The daughter of a father with hemophilia and a carrier mother has a __________ probability of having hemophilia. (Concept

50%

15:A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way: A woman with this defect typically has small patches of skin with sweat glands and other patches without sweat glands. In women, the pattern of sweat-gland distribution can best be explained by __________. (Concept

X chromosome inactivation

31:Cells that have an abnormal number of some particular chromosome are said to be __________.(Concept

aneuploid

36:When a person has Down syndrome, he or she has an extra chromosome 21. Therefore, Down syndrome is a kind of __________ and results from __________. (Concept

aneuploidy ... nondisjunction of chromosome 21

24:In a particular species of mammal, black hair (B) is dominant to green hair (b), and red eyes (R) are dominant to white eyes (r). When a BbRr individual was mated with a bbrr individual, the observed distribution of offspring was as follows: black-red 1,070; black- white 177; green-red 180; green-white 1,072. Based on these data, what is the recombination frequency? (Concept

approx. 14%

20:A gray-bodied, vestigial-winged fly is crossed with a black-bodied, normal-winged fly. The F 1 progeny is testcrossed. Among the resulting offspring, __________ is a parental type, and __________ is a recombinant type. (Concept

black-bodied, normal-winged ... black-bodied, vestigial-winged

Both chloroplasts and mitochondria ___________.

carry ed by mitochondrial DNA. Which of the following observations would be the most decisive evidence against this idea?(

39:Which type of chromosomal alteration is responsible for the cri du chat syndrome?(Concept

deletion

41:Genomic imprinting in mammals appears to affect primarily genes involved in __________.(Concept

embryonic development

43:It is proposed that a certain disorder affecting the inner ear is caused by mitochondrial DNA. Which of the following observations would be the most decisive evidence against this idea?(

fathers with the disorder pass it on to all their children, but mothers with the disorder do not pass it along

22:The recombination frequency between two gene loci is __________. (Concept

greater as the distance between the two loci increases

If a woman is heterozygous for a recessive sex-linked allele and her husband has the dominant allele, which one of the following is true about the probabilities for their children?

half of their sons will show the recessive traits=