ch 11-12

Which of the following describes the ability of a single gene to have multiple phenotypic effects? incomplete dominance pleiotropy epistasis multiple alleles

b

A man with type A blood marries a woman with type B blood. Their child has type O blood. 1. What is the genotype of the man? ii I A i I B i I A I A 2. What is the genotype of the woman? ii I A i I B i I B I B 3. What is the genotype of the child? ii I A i I B i I A I B 4.What genotypes would you expect in future offspring from this marriage? Select all that apply. ii I A i I B i I A I A I B I B I A I B 5. In what frequencies would you expect the offspring genotypes? Indicate the frequency of each genotype by dragging the labels to the table. Labels may be used once, more than once, or not at all. ALL 1/4

-I A i -I B i -ii -ii I A i I B i I A I B

Part complete In certain plants, the tall trait is dominant to the short trait. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short? 1 1/2 1/4 1/6 0

0

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits is a dominant trait. What fraction of this couple's children would be expected to have extra digits? Express your answer using the slash symbol and no spaces (for example, 1/16).

1/2

Skin color in a certain species of fish is inherited via a single gene with four different alleles. One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then what proportion of their offspring would be expected to have five units of color? 1/4 0 1/5 1/2 1/8

1/2

Use the following information to answer the questions below. Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers? 250 750 565 190 65

190

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. How many genes must be responsible for these coat colors in Labrador retrievers? 1 5 4 3 2

2

In tigers, a recessive allele that is pleiotropic causes an absence of fur pigmentation (a white tiger) and a cross-eyed condition. If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? Express your answer using the percent symbol and no spaces (for example, 10%). Part B Part complete What percentage of cross-eyed tigers will be white? Express your answer using the percent symbol and no spaces (for example, 10%).

25% 100%

Use the following information to answer the questions below. Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. Among the F2 offspring, what is the probability of plants with white axial flowers? 9/16 1/16 1/8 3/16 1/4

3/16

Which of the following do you expect if an individual is heterozygous for the sickle-cell trait? He or she will show some symptoms of the disease. He or she will have full-blown sickle-cell disease because the allele is dominant. He or she will not develop sickle-cell disease. He or she will be more apt to acquire a serious case of malaria. None of the listed responses is correct.

A

Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not have the disorder. The dominant allele for the gene determining the disorder represses protein production from the recessive allele. In a recessive disorder, only a single functioning allele is necessary to determine a normal phenotype. Affected individuals have recessive mutations, but a carrier has a dominant mutation.

B

What do we mean when we use the term monohybrid cross? A monohybrid cross is performed for one generation. A monohybrid cross involves organisms that are heterozygous for one character. A monohybrid cross produces a single offspring. A monohybrid cross results in a 9:3:3:1 phenotype ratio in the F2 offspring. A monohybrid cross involves a single parent.

B

A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the albino is crossed with a second black one, 7 blacks and 5 albinos are obtained. What is the best explanation for this genetic outcome? Albino (C A ) and black (C B ) exhibit incomplete dominance. Albino (b) is a recessive trait; black (B) is a dominant trait. Albino (A) is a dominant trait; black (a) is a recessive trait. Albino (A) and black (B) exhibit codominance. What are the genotypes of the parents in the first cross (the cross that produced 12 black offspring)? BB x BB BB x Bb BB x bb Bb x Bb Bb x bb bb x bb What are the genotypes of the gametes and offspring in the first cross? gametes: all B; offspring: all BB gametes: B and b; offspring: all Bb gametes: all b; offspring: all bb What are the genotypes of the parents in the second cross (the cross that produced 7 black and 5 albino offspring)? BB x BB BB x Bb BB x bb Bb x Bb Bb x bb bb x bb What are the genotypes of the gametes and offspring in the second cross? gametes: all B; offspring: all BB gametes: all b; offspring: all bb gametes: 1/2 B and 1/2 b (heterozygous parent) and b; offspring: all Bb gametes: 1/2 B and 1/2 b (heterozygous parent) and b; offspring: 1/2 Bb and 1/2 bb

B C B E D

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible phenotype for the father? A negative O negative AB negative B positive impossible to determine

B positive

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct? These homologous chromosomes are formed by DNA replication. Each of these homologous chromosomes consists of a single chromatid. Therefore, they must come from a haploid cell. These homologous chromosomes represent a maternal and a paternal chromosome.

C

Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation. In a set of 16 individuals from the F2 generation, 3 will produce wrinkled yellow seeds. Wrinkled and yellow traits are linked in peas. The chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%.

C

When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other? The dominant allele prevents transcription of the recessive allele. The dominant allele prevents expression of the recessive allele by an unknown mechanism. They do not interact at all.

C

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. If both children are of blood type M, which of the following is possible? Each parent must be type M. Each parent is either M or MN. The MN blood group is recessive to the ABO blood group. Neither parent can have the N allele. Both children are heterozygous for this gene.

Each parent is either M or MN.

A translocation causes which of the following results? exchange of nonhomologous chromosome fragments exchange of homologous chromosome fragments nondisjunction deletion only

a

All but one of the following diseases/disorders is the result of chromosomal alterations. Mosaicism Down syndrome (Trisomy 21) Cri du chat syndrome Turner syndrome Chronic myelogenous leukemia (CML)

a

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

a

Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true? View Available Hint(s) It is very likely that at least one of Woody Guthrie's parents also had the allele for Huntington's disease. His daughters will die of Huntington's disease but not his sons. His sons will develop Huntington's disease but not his daughters. All of his children will develop Huntington's disease. There is not enough information to answer the question.

a

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (CRCr) offspring of red (CRCR) and white (CrCr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white? roan × roan white × roan red × roan red × white

a

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual? 47, +21 45, X 47, XXY 47, XXX 47, XYY

a

Tallness (T) in snapdragons is dominant to dwarfness (t), and red (CR) flower color is not dominant to white (Cr). The heterozygous condition results in pink (CRCr) flower color. A dwarf red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals? TtCRCrtall and pink TtCRCrtall and red ttCrCrdwarf and white ttCRCrdwarf and pink TTCRCRtall and red

a

Which of the following is a situation in which the chromosome number is either 2_n_+1 or 2_n_-1? aneuploidy gene linkage polyploidy methylation inversion

a

Which of the following statements correctly describes aneuploid conditions? Monosomy X is the only known viable human monosomy. Of all human aneuploidies, only Down syndrome is associated with mental retardation. A monosomy is more frequent than a trisomy. An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

a

Why does recombination between linked genes continue to occur? New allele combinations are acted upon by natural selection. Recombination must occur or genes will not assort independently. Without recombination there would be an insufficient number of gametes. Recombination is a requirement for independent assortment.

a

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

b

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this expression of phenotypes? incomplete dominance pleiotropy codominance multiple alleles epistasis

b

Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females? Males would display this disorder with greater frequency than females. Females would display this disorder with greater frequency than males. Males and females would display this disorder with equal frequency.

b

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system? 1 4 8 16 2

b

The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following concepts? Mendel's law of independent assortment Darwin's explanation of natural selection Darwin's observations of competition Mendel's law of segregation

b

Use the following information to answer the questions below. Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. In the F2 generation of the above cross, which of the following phenotypic ratios would be expected? 9:3:3:1 6:3:3:2:1:1 1:1:1:1 1:1:1:1:1:1 9:4:3

b

What do we mean when we use the term dihybrid cross? A dihybrid cross involves two parents. A dihybrid cross involves organisms that are heterozygous for two characters. A dihybrid cross is performed for two generations. A dihybrid cross results in a 3:1 phenotype ratio in the F2 offspring. A dihybrid cross produces two offspring.

b

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

b

What is the source of the extra chromosome 21 in an individual with Down syndrome? nondisjunction in the mother only nondisjunction or translocation in either parent nondisjunction in the father only duplication of the chromosome

b

What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction? polyploidy an inversion a deletion a nondisjunction a translocation

b

Which of the following is true of an X-linked gene but not of a Y-linked gene? It does not segregate like other genes. The gene is present in both males and females. It is expressed in half of the cells of either males or females. It is only expressed in female offspring. Sister chromatids separate during mitosis.

b

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of independent assortment? Sister chromatids separate during anaphase II. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

b

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties? The traits blended together during fertilization. One allele was dominant. Each allele affected phenotypic expression. Phenotype was not dependent on genotype. No genes interacted to produce the parental phenotype.

b

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. They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes? 75% 0% 100% 50% 25%

c

At what point in cell division is a chromosome lost so that, after fertilization with a normal gamete, the result is an embryo with 45,X? after an error occurring in prophase I only after an error occurring in anaphase II only after an error occurring in anaphase I or anaphase II after an error occurring in metaphase II only after an error occurring in anaphase I only

c

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition? One-half of the daughters of an affected man would have this condition. Women can never have this condition. Very rarely: it is rare that an affected male would mate with a carrier female. Only if a woman is XXX could she have this condition. One-fourth of the daughters of an affected father and a carrier mother could have this condition.

c

How are human mitochondria inherited? as an X-linked trait as linear DNA from the mother only from the father only without DNA

c

Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes eye problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information? It is dominant. It is epistatic. It is pleiotropic. It is recessive.

c

Mendel's second law of independent assortment has its basis in which of the following events of meiosis I? separation of cells at telophase separation of homologs at anaphase alignment of synapsed pairs of homologous chromosomes on the metaphase plate crossing over synapsis of homologous chromosomes

c

Select the correct statement(s) about sex determination in animals. Select all that apply. In all animals, males are XY and females are XX. In all animals, males have the SRY gene and females lack this gene. The mechanism of sex determination varies with different animal species.

c

Tallness (T) in snapdragons is dominant to dwarfness (t), and red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio? 27:9:9:9:3:3:3:1 1:2:1 6:3:3:2:1:1 9:3:3:1 9:4:3

c

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following? None of the traits obeyed the law of segregation. All of the genes controlling the traits were located on the same chromosome. All of the genes controlling the traits behaved as if they were located on different chromosomes. Some traits obeyed the law of segregation and some did not.

c

Use the following information to answer the questions below. Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to be which of the following? purple and oval white and long purple and long red and oval red and long

c

What is the likelihood that the offspring of IV-3 and IV-4 will have the trait? 0% 25% 50% 75% 100%

c

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

c

Which of the following events causes recombination between linked genes to occur? When genes are linked they always "travel" together at anaphase. Nonrecombinant chromosomes break and then re-join with one another. Crossovers between these genes result in chromosomal exchange. Mutation on one homolog is different from that on the other homolog.

c

Which of the following statements correctly describes linkage? 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%. 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.

c

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation? Sister chromatids separate during anaphase II. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

c

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 their daughters might be expected to be color-blind dwarfs? half one out of four all none three out of four

d

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. What proportion of their sons would be color-blind and of normal height? all one out of four three out of four half none

d

A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Which of the following statements describes the best use of this discovery? Introduce a normal allele into deficient newborns. Follow the segregation of the allele during meiosis. Screen all newborns of an at-risk population. Design a test for identifying heterozygous carriers of the allele.

d

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype? masculine characteristics such as facial hair sterile female enlarged genital structures healthy female of slightly above-average height

d

From this pedigree, how does this trait seem to be inherited? as a recessive trait as an incompletely dominant trait as a result of epistasis as a dominant trait from mothers

d

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others produce pink flowers. This can be best explained by which of the following statements? The allele for blue hydrangea is completely dominant. Multiple alleles are involved in the expression of the phenotype. The alleles are codominant. Environmental factors such as soil pH affect phenotype.

d

In general, the frequency with which crossing over occurs between two linked genes depends on __________. View Available Hint(s) whether the genes are dominant or recessive the phase of meiosis in which the crossing over occurs whether the genes are on the X or some other chromosome how far apart they are on the chromosome the characters the genes code for

d

In humans, what determines the sex of offspring, and why? The female gamete determines sex because only the female gametes can have one of two functional sex chromosomes. The male determines sex because the sperm can fertilize either a female egg or a male egg. The female gamete determines sex because only the female gamete provides cytoplasm to the zygote. The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome. The chromosome contribution from both parents determines sex because the offspring uses all the parents' chromosomes.

d

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division? metaphase I of meiosis prophase I of meiosis anaphase II of meiosis anaphase I of meiosis

d

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

d

What is the genotype of individual II-5? WW or ww Ww ww or Ww ww WW

d

What is the probability that individual III-1 is Ww? 2/3 2/4 3/4 1 1/4

d

Which of the following statements describes one difference between the law of independent assortment and the law of segregation? The law of segregation explains the segregation of two or more genes relative to one another. The law of segregation requires having two or more generations to describe. The law of segregation is accounted for by anaphase of mitosis. The law of independent assortment explains the segregation of two or more genes relative to one another.

d

Which of the following statements provides an example of epistasis? In cacti, there are several genes for the type of spines. Recessive genotypes for each of two genes (aabb) result in an albino corn snake. In Drosophila (fruit flies), white eyes can be due to a combination of multiple genes. In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.

d

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible genotype for the mother? IAIB IBIB IAIA ii IAi

e

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible partial genotype for the son? IAIB IBIB ii IAIA IBi

e

Down syndrome has a frequency in the U.S. population of ~1/830 live births. In which of the following groups would you expect this frequency to be significantly higher? people in Latin or South America people living in equatorial areas of the world the Inuit and other peoples in very cold habitats very small population groups No groups have a significantly higher frequency.

e

The flower color trait in radishes is an example of which of the following? epistasis codominance sex linkage a multiple allelic system incomplete dominance

e

Use the following information to answer the questions below. Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. These results indicate which of the following? Brown is dominant to black. Black is dominant to brown and to yellow. There is incomplete dominance. Yellow is dominant to black. Epistasis is involved.

e

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants? Genes are composed of DNA. There is considerable genetic variation in garden peas. An organism that is homozygous for many recessive traits is at a disadvantage. Recessive genes occur more frequently in the F1 generation than do dominant ones. Traits are inherited in discrete units, and are not the results of the "blending" of traits.

e

Which of the following traits is an example of polygenic inheritance? Huntington's disease in humans pink flowers in snapdragons the ABO blood group in humans white and purple flower color in peas skin pigmentation in humans

e

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. In one cross of black × black, the results were as follows: 9/16 black, 4/16 yellow, 3/16 brown The genotype eebb must result in which of the following? white black yellow a lethal result brown

yellow

Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white. Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies? yyBB and yyBb yyBB and yybb yyBb and yybb yyBB and yyBB yyBb and yyBb

yyBb and yyBb