Bio 311 Ch. 4 & Ch. 5
Match each phenotype description to its corresponding sex chromosome genotype in humans. - XO with SRY on an autosome? - XO? - XXX? - XXY? - XYY? Answer bank: A. female with Turner syndrome B. phenotypically male with sterility and hypogonadism C. phenotypically female with some abnormalities and overexpression of X chromosome genes D. phenotypically male with an increase in average stature E. phenotypically male but karyotype indicates presence of only X chromosome
- XO with SRY on an autosome? E. phenotypically male but karyotype indicates presence of only X chromosome - XO? A. female with Turner syndrome - XXX? C. phenotypically female with some abnormalities and overexpression of X chromosome genes - XXY? B. phenotypically male with sterility and hypogonadism - XYY? D. phenotypically male with an increase in average stature
Hemophilia is called "the royal disease" because many European royal families had members with the condition. Hemophilia is a recessive, X‑linked disorder. Queen Victoria was unaffected by hemophilia, but was a carrier of the hemophilia gene (X^HX^h). Suppose Queen Victoria's husband, Prince Albert, was affected with hemophilia (X^hY). 1. What is the percent probability that a son of Queen Victoria and Prince Albert would be unaffected by hemophilia? - probability of unaffected son: ________ %? 2. What is the percent probability that a daughter or son of Queen Victoria and Prince Albert would be affected by hemophilia? - probability of affected child: ________ %? 3. What is the percent probability Queen Victoria and Prince Albert would have two affected females? - probability of two affected females: ________ %?
1. 50% 2. 50% 3. 6.25%
A black female cat is mated with an orange male cat. They produce two tortoiseshell females, two black males, one orange female, and one tortoiseshell male, for a total of six kittens. Orange and black fur color are encoded by different alleles of the same X‑linked fur color gene. 1. Based on the phenotypes of the parents, what sex chromosomes do the orange female and the tortie male offspring have? A. The orange female has two X chromosomes, and the tortoiseshell male is YO. B. The orange female is missing one X chromosome, and the tortoiseshell male has one Y chromosome and more than one X chromosome. C. The orange female is missing one X chromosome, and the tortoiseshell male is XY. D. The orange female is XX, and the tortoiseshell male is XXY. 2. Select the most likely explanations for the sex chromosome types. [Select all that apply.] - The tortoiseshell male has only one X chromosome, and it carries the black allele. - Random X inactivation in XXY causes orange and black patches in the tortoiseshell male. - The orange female received an orange X chromosome from her father and no X chromosome from her mother. - The orange female has two X chromosomes, and the black X from her mother is inactivated.
1. B. The orange female is missing one X chromosome, and the tortoiseshell male has one Y chromosome and more than one X chromosome. 2. - Random X inactivation in XXY causes orange and black patches in the tortoiseshell male. - The orange female received an orange X chromosome from her father and no X chromosome from her mother.
Color blindness is a sex‑linked recessive trait. A female is color blind in one eye, but not both. 1. Select the explanation for this condition. A. female has XO genotype B. silencing of different X chromosomes C. all X chromosomes are inactivated 2. Is it possible for a male to have different color‑blindness phenotypes in each eye? A. yes, in an XXY male with a different active X in each eye B. yes, in an XYY male with a different active Y in each eye C. no, since trisomy of the sex chromosomes is lethal D. no, since XXY males inactivate both X chromosomes
1. B. silencing of different X chromosomes 2. A. yes, in an XXY male with a different active X in each eye
In certain salamanders, the sex of a genetic female can be altered, changing her into a functional male; these salamanders are called sex‑reversed males. When a sex‑reversed male is mated with a normal female, approximately 2/3 of the offspring are female, and 1/3 are male. 1. Given this observation, which of the statements is most likely to be true for these salamanders? A. Females are the homogametic sex. B. They exhibit hermaphroditism. C. Females are the heterogametic sex. D. They exhibit genic sex determination. E. Males are the heterogametic sex. 2. How do you explain the results of this cross? A. The female parent had two Z chromosomes. B. Both parents were ZW, and WW offspring did not survive. C. The sex‑reverse parent was ZZ, the female parent was ZW, and ZW offspring did not survive. D. The sex‑reverse male parent had two W chromosomes. Q
1. C. Females are the heterogametic sex. 2. B. Both parents were ZW, and WW offspring did not survive.
Suppose a novel disease has been studied in several families and is known to be caused by a mutation in one gene. The given table shows families where the disease is present. The four rightmost columns record the number of offspring in each family. 1. Select the most likely mode of inheritance of the disease. A. autosomal recessive B. autosomal dominant C. X‑linked dominant D. X‑linked recessive 2. Select the description that best matches the female parent in family 6. A. has two disease alleles B. has no disease alleles C. has one disease allele 3. Select the description that best matches the male parent in family 3. A. has two disease alleles B. has one disease allele C. has no disease alleles
1. C. X-linked dominant 2. C. has one disease allele 3. C. has no disease alleles
In a hypothetical insect species, eye color may be purple or red and wings may be long or short. The table shows the results of two crosses where the parents were obtained from a mixed population that did not breed true. Parents: Progeny: Cross 1: red, long male × red, long female males: one‑half red, long; one‑half red, short females: all red, long Cross 2: red, short male × purple, long female males: one‑half red, long; one‑half red, short females: one‑half red eyed, long; one‑half red eyed, short 1. What is the mode of inheritance for eye color in this insect? A. The eye‑color gene is X‑linked, and purple is dominant to red. B. The eye‑color gene is X‑linked, and red is dominant to purple. C. The eye‑color gene is autosomal, and purple is dominant to red. D. The eye‑color gene is autosomal, and red is dominant to purple. 2. What is the mode of inheritance for wing size in this insect? A. The wing size gene is autosomal, and long is dominant to short. B. The wing size gene is X‑linked, and long is dominant to short. C. The wing size gene is X‑linked, and short is dominant to long. D. The wing size gene is autosomal, and short is dominant to long. 3. Assuming that true breeding lines are used, which cross would produce an F2 generation that confirms the mode of inheritance for both traits? A. red, short male × purple, short female B. red, long male × red, short female C. purple, short male × purple, short female D. red, short male × purple, long female 4. Which phenotypic ratio would you expect to see in the F2 generation of the cross you selected? A. males: 3/8 red, long; 3/8 red, short; 1/8 purple, long; 1/8 purple, short females: 3/8 red, long; 3/8 red, short; 1/8 purple, long; 1/8 purple, short B. males: 3/8 red, long; 3/8 red, short; 1/8 purple, long; 1/8 purple, short females: 3/4 red, long; 1/4 purple, long C. males: 3/4 red, long; 1/4 purple, long females: 3/8 red, long; 3/8 red, short; 1/8 purple, long; 1/8 purple, short D. males: 9/16 red, long; 3/16 red, short; 3/16 purple, long; 1/16 purple, short females: 9/16 red, long; 3/16 red, short; 3/16 purple, long; 1/16 purple, short
1. D. The eye‑color gene is autosomal, and red is dominant to purple. 2. B. The wing size gene is X‑linked, and long is dominant to short. 3. D. red, short male × purple, long female 4. B. males: 3/8 red, long; 3/8 red, short; 1/8 purple, long; 1/8 purple, short females: 3/4 red, long; 1/4 purple, long
1. Select the definition of a Barr body. A. an active X chromosome B. an active autosome C. an active Y chromosome D. an inactive X chromosome The first cloned cat, CarbonCopy (CC), was tabby, while the cat she was cloned from, Rainbow, was calico. The surrogate mother was a tabby. 2. Select the explanation that best explains why CC would never have been identical in pattern to Rainbow. A. Both X chromosomes remain actively transcribed. B. During embryogenesis, one X chromosome is randomly inactivated in each cell lineage. C. The coat color genes are maternal effect genes, so CC looked like the surrogate. D. The coat color genes are on the mitochondrial genome and inherited with the mother's oocyte.
1. D. an inactive X chromosome 2. B. During embryogenesis, one X chromosome is randomly inactivated in each cell lineage.
Use the Punnet Squares interactive, Level 3 to conduct a cross between a man with normal vision and a woman with the gene for color blindness. 1. A man with normal vision, XB Y, and a woman who is a carrier for color blindness, XB Xb, mate. How many total phenotypes result from this cross? 2. What percentage of male offspring will be color‑blind? color‑blind male offspring? 3. If the mother were color‑blind, what percentage of male offspring would be color‑blind?
1. number of phenotypes: - 3 phenotypes 2. color-blind male offspring: - 50% 3. color-blind male offspring: - 100%
A eukaryotic diploid cell from an organism with the XX-XO sex determination system has two pairs of autosomes and one X chromosome. One pair of autosomes has a heterozygous locus with alleles A and a. The other pair of autosomes has a heterozygous locus with alleles B and b. What is the probability of a gamete from this individual having this genotype: alleles a and b, without chromosome X? A. 1/8 B. 1/16 C. 1/4 D. 1/2
A. 1/8
If a homozygous plant with red peppers is crossed with a homozygous plant with cream peppers, all the F1 plants will have red peppers. When the F1 are crossed with each other, the F2 shows a ratio of: A. 9:3:3:1 B. 9:3:4 C. 3:1 D. 9:7
A. 9:3:3:1
Which statements describe Y‑linked traits? [Select all that apply.] A. All male offspring of affected fathers will express the trait. B. Males have a higher probability of inheriting the trait from their mothers. C. At least 50% of the male and female offspring will inherit the trait. D. Female offspring cannot inherit the trait. E. A carrier female has a 25% chance of having a carrier daughter.
A. All male offspring of affected fathers will express the trait. D. Female offspring cannot inherit the trait.
Assume that a mutation occurs in the Xist gene of a XY male that makes the gene inactive. What would you expect would be the phenotypic consequences of this mutation for the male? A. He would probably have no phenotypic consequences. B. He would probably not survive because all his X-linked genes would be turned off. C. He would not have expression of some of his autosomal genes. D. He would have enhanced expression of his Y-linked genes.
A. He would probably have no phenotypic consequences.
Why are tortoiseshell cats are almost always female? A. The result is from the random inactivation of one X chromosome. B. The result is from a particular homozygous genotype. C. The allele for tortoiseshell fur color is located on a single X chromosome. D. It is the result of a particular Y-linked characteristic.
A. The result is from the random inactivation of one X chromosome.
Suppose researchers identified two Drosophila melanogaster mutant phenotypes. One phenotype is called thistle and the other is called coffee. In order to determine the mode of inheritance of the mutant allele responsible for each phenotype, males that have both mutant phenotypes are mated with wild‑type (wt) females to produce F1 progeny. Then, the F1 progeny are mated together and the F2 progeny are scored. What is the mode of inheritance for the genes controlling thistle and coffee? A. autosomal dominant for thistle and X‑linked recessive for coffee B. X‑linked dominant for thistle and X‑linked recessive for coffee C. autosomal recessive for thistle and autosomal recessive for coffee D. autosomal dominant for thistle and X‑linked dominant for coffee What is the genotype of the original male parent? A. heterozygous mutant at one locus and hemizygous mutant at the other locus B. homozygous mutant at both loci C. hemizygous mutant at both loci D. homozygous mutant at one locus and hemizygous mutant at the other locus
A. autosomal dominant for thistle and X‑linked recessive for coffee D. homozygous mutant at one locus and hemizygous mutant at the other locus
An X chromosome that expresses the Xist gene will likely A. become inactivated. B. remain activated. C. repress the other X chromosome in the cell. D. be degraded.
A. become inactivated.
What is the role of Mullerian-inhibiting substance in human development? A. causes the degeneration of female reproductive ducts B. causes the testes to secrete hormones C. causes the neutral gonads to develop into ovaries D. causes the degeneration of male reproductive ducts
A. causes the degeneration of female reproductive ducts
A boy has blood type MN with a genotype of LMLN. His red blood cells possess both the M antigen and the N antigen. What is the relationship between his two alleles for this gene? A. codominance B. epistasis C. complementation D. incomplete dominance E. complete dominance
A. codominance
Which type of dominance occurs when the heterozygote includes the phenotypes of both homozygotes? A. codominance B. overdominance C. incomplete dominance D. complete dominance
A. codominance
Fur color in a species of mouse is controlled by a single gene pair. BB animals are black and bb animals are white. Bb animals have gray fur and each hair is gray. What type of interaction is being shown by the two alleles in heterozygous animals? A. incomplete dominance B. epistasis C. complementation D. codominance E. complete dominance
A. incomplete dominance
Continuous characteristics that are both polygenic and influenced by environmental factors are called which of these? A. multifactorial characteristics B. epistatic characteristics C. phenocopies D. epigenetic characteristics
A. multifactorial characteristics
In butterflies, sex is determined by the ZW sex‑determination system. Female butterflies are heterogametic and have both a Z sex chromosome and a W sex chromosome for sex determination. In contrast, male butterflies are homogametic and have two Z sex chromosomes. Select all of the relatives from which a female butterfly could have inherited her Z sex chromosome. A. paternal grandmother B. maternal grandfather C. mother D. father
A. paternal grandmother D. father
Incomplete _____ occurs when the genotype does not always produce the expected phenotype. A. penetrance B. pleiotropy C. dominance D. expressivity
A. penetrance
What is the definition of recessive epistasis? A. where the presence of two recessive alleles (the homozygous genotype) inhibits the expression of an allele at a different locus B. where genes at different loci contribute to the determination of a single phenotypic characteristic C. where two recessive alleles at either of two different loci are capable of suppressing a phenotype D. where only a single copy of an allele is required to inhibit the expression of an allele at a different locus
A. where the presence of two recessive alleles (the homozygous genotype) inhibits the expression of an allele at a different locus
An individual with Turner syndrome has how many Barr bodies? A. zero B. one C. two D. three
A. zero
Identify the chromosomal disorders affecting the patients in the Abnormal Karyograms tab of the karyotype interactive. Place each patient according to whether his or her disorder occurs exclusively in biological males, exclusively in biological females, or in both sexes. - Affects only biological males? - Affects only biological females? - Affects both sexes? Answer bank: - patient 768 - patient 367 - patient 251 - patient 892
Affects only biological males? - patient 892 Affects only biological females? - patient 367 Affects both sexes? - patient 768 - patient 251
Calvin Bridges determined that the rare white‑eyed males produced from the mating of true‑breeding red‑eyed females with white‑eyed males resulted from a nondisjunction of X chromosomes in the female parent during meiosis. If such a mating produced 1234 red‑eyed progeny and three white‑eyed males, what is the observed rate of nondisjunction of the X chromosomes? A. 0.97% B. 0.24% C. 0.12% D. This is impossible to calculate with the given information. E. 0.49%
B. 0.24%
In goats, a beard is produced by an autosomal allele that is dominant in males and recessive in females. We'll use the symbol Bb for the beard allele and B+ for the beardless allele. Another independently assorting autosomal allele that produces a black coat (W) is dominant over the allele for white coat (w). Give the phenotypes and their expected proportions for the cross B+Bb ww male × BbBb Ww female. A. 1/8 beardless black females, 1/8 beardless white females, 1/8 bearded black females, 1/8 bearded white females, 1/8 bearded black males, 1/8 bearded white males, 1/8 beardless black males, 1/8 beardless white males B. 1/8 beardless black females, 1/8 beardless white females, 1/8 bearded black females, 1/8 bearded white females, 1/4 bearded black males, 1/4 bearded white males C. 1/16 beardless black females, 3/16 beardless white females, 1/8 bearded black females, 1/8 bearded white females, 1/8 bearded black males, 1/8 bearded white males, 1/8 beardless black males, 1/8 beardless white males D. 1/4 beardless black females, 1/4 beardless white females, 1/4 bearded black males, 1/4 bearded white males
B. 1/8 beardless black females, 1/8 beardless white females, 1/8 bearded black females, 1/8 bearded white females, 1/4 bearded black males, 1/4 bearded white males
Red-green color blindness is an X‑linked recessive trait in humans. Polydactyly (extra fingers and toes) is an autosomal dominant trait. Martha has normal fingers and toes and normal color vision. Her mother is normal in all respects, but her father is color blind and polydactylous. Bill is color blind and polydactylous. His mother has normal color vision and normal fingers and toes. When answering the given question, consider that the answers include the proportions of only some of the possible phenotypes; other phenotypes are also expected to occur but are not included. If Bill and Martha marry, what proportions of children with specific phenotypes would they be expected to produce? A. 1/4 color‑blind girls with normal fingers, 1/4 boys with normal vision and polydactyly B. 1/8 color‑blind girls with polydactyly, 1/8 boys with normal vision and normal fingers C. 1/4 girls with normal vision and polydactyly, 1/8 boys with normal vision and polydactyly D. 1/8 color‑blind girls with normal fingers, 1/4 boys with normal vision and polydactyly
B. 1/8 color‑blind girls with polydactyly, 1/8 boys with normal vision and normal fingers
How many genotypes are possible at a locus with five alleles? A. 5 B. 15 C. 10 D. 12
B. 15
The very rare Bombay blood phenotype in humans (first discovered in Bombay, India) results in type O blood because of the lack of both the A and B antigens in individuals who are of hh genotype. This genotype results in blood type O blood regardless of the genotype at the unlinked I locus. If two parents are both of IAIB Hh genotype (type AB blood), what is the probability that their first child will also have the AB blood type? A. 3/4 B. 3/8 C. 1/4 D. 1/162
B. 3/8
With a locus that contains five alleles, how many different homozygotes can there be? A. 32 B. 5 C. 10 D. 1
B. 5
In Morgan's experiments involving white-eyed fruit flies (see panel (a) of Figure 4.12), which generation of fly crosses supported the hypothesis that white eyes were sex-linked? [Click on the image to view full size.] A. P generation B. F2 generation C. F1 generation D. F3 generation
B. F2 generation
Identical, or monozygotic, twins develop from a single egg fertilized by a single sperm. Monozygotic twins are genetically identical because they originate from a single zygote that split into two. Caroline Loat and her colleagues examined nine measures of social, behavioral, and cognitive ability in 1000 pairs of both male and female identical twins. Their study found that pairs of male twins tended to be more alike in their prosocial behavior, peer problems, and verbal ability scores than pairs of female twins. Which statement explains this observation? A. Interacting genes on the X and Y chromosomes in the brains of males results in identical twins with more similar behaviors. B. Females are mosaic for the expression of heterozygous X‑linked loci, because females undergo random X‑inactivation. C. Identical male twins express the same X‑linked alleles in their neural cells, because males undergo random X‑inactivation. D. Male twins have similar expression levels of X‑linked genes, because the Y chromosome silences expression of X chromosome genes.
B. Females are mosaic for the expression of heterozygous X‑linked loci, because females undergo random X‑inactivation.
An X‑linked recessive gene causes red-green color blindness in humans. Suppose John and Cathy have normal color vision. After 10 years of marriage to John, Cathy has given birth to a color‑blind daughter and a color*#8209;blind son. John filed for divorce, claiming that he is not the father of at least one of the children. Which statement describes John's paternity claim? A. He could be the father of both children. B. He cannot be the father of Cathy's daughter. C. He cannot be the father of Cathy's son. D. He cannot be the father of either child.
B. He cannot be the father of Cathy's daughter.
What blood genotype is considered the universal receiver? A. IAi B. IAIB C. ii D. IBi
B. IAIB
Since the white‑eye trait is X‑linked recessive, what result would you expect when crossing a heterozygous red‑eyed female with a white‑eyed male? A. all red‑eyed progeny B. In each sex, half of the offspring will have red and half of the offspring will have white eyes. C. all red‑eyed females and all white‑eyed males D. all red‑eyed females with half of the males having white and half of the males having red eyes E. all red‑eyed males with half of the females having white and half of the females having red eyes
B. In each sex, half of the offspring will have red and half of the offspring will have white eyes.
Why are most sex-linked characteristics X-linked? A. Both males and females have an X chromosome. B. The Y chromosome contains little genetic information. C. The pattern of inheritance for sex-linked characteristics is identical to that exhibited by genes located on autosomes. D. Most sex-linked disorders affect females.
B. The Y chromosome contains little genetic information.
In a cross between a white‑eyed female with two X chromosomes and one Y chromosome (XwXwY) with a red‑eyed male, the majority of the males have white eyes and the majority of the females have red eyes. However, rare red‑eyed males and white‑eyed females are present as well. What is the most likely chromosomal constitution of the red‑eyed males and white‑eyed females resulting from this cross? A. X+Y males and XwXw females B. X+Y males and XwXwY females C. X+XwY females and Xw males D. XwY males and XwX+ females E. X+XwY males and Xw females
B. X+Y males and XwXwY females
In the animation, the rare white‑eyed males generated from offspring of true‑breeding red‑eyed females and white‑eyed males were the result of a nondisjunction of X chromosomes in the female during meiosis I. Could white‑eyed males be generated in this cross by a nondisjunction of X chromatids in the female during meiosis II? Why or why not? A. No, if a nondisjunction of X chromatids occurred in meiosis II of a female, all progeny would have red eyes. B. Yes, because a nondisjunction of X chromatids in meiosis II of a female will generate two abnormal gametes, one with two X chromosomes and one with no X chromosome. C. No, if a nondisjunction of X chromatids occurred in meiosis II of a female, none of the resulting offspring would be viable. D. No, if a nondisjunction of X chromatids occurred in meiosis II of a female, only white-eyed females could be generated. E. Yes, because a nondisjunction of X chromatids in meiosis II of a female will result in both white-eyed males and white-eyed females.
B. Yes, because a nondisjunction of X chromatids in meiosis II of a female will generate two abnormal gametes, one with two X chromosomes and one with no X chromosome.
The Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two sons who die of bleeding after circumcision (removal of the foreskin from the penis), any additional sons that she has should not be circumcised. The bleeding is most likely due to the X‑linked disorder hemophilia. Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should be. Is this religious law consistent with sound genetic principles? A. Yes, the woman is likely to be homozygous for the hemophilia allele since she has two sons with the disorder. Her sisters and her brothers are also likely to carry the mutant allele with both at risk for having affected sons. B. Yes, the woman is a carrier and half of her sons will be affected. Her sisters may also be carriers, but her brothers' sons will get their X chromosomes from their mothers, who are unlikely to be carriers of the allele. C. No, the woman is likely a carrier for the mutant allele, which would mean that half of her brothers are expected to carry this allele also and be at risk of having affected sons. Her sisters are likely to be homozygous normal and not at risk of having affected sons. D. No, the sons of both the woman's sisters and her brothers should be not circumcised. The allele for hemophilia is segregating in her family, and both her sisters and brothers may carry it and their sons may inherit it. E. No, the woman is a carrier for hemophilia, but her sisters are likely to be homozygous for the normal allele since it is unlikely that two sisters in the same family could both be both carriers and have affected sons.
B. Yes, the woman is a carrier and half of her sons will be affected. Her sisters may also be carriers, but her brothers' sons will get their X chromosomes from their mothers, who are unlikely to be carriers of the allele.
What is the phenomenon called where there is stronger or earlier expression of a genetic trait in succeeding generations? A. epistasis B. anticipation C. pleiotrophy D. variable expressivity E. reduced penetrance
B. anticipation
Characteristics that exhibit many overlapping phenotypes are called _____ characteristics. A. discontinuous B. continuous C. polygenic D. dominant pleiotropic
B. continuous
The results of which of these crosses allowed T. H. Morgan to conclude that the white‑eye trait in Drosophila was not autosomal recessive? A. crosses between true‑breeding red‑eyed females and red‑eyed males B. crosses between true-breeding white‑eyed females and red‑eyed males C. crosses between true‑breeding red‑eyed females and white‑eyed males D. None of the crosses would give a different result than what would be expected if the white‑eye trait was autosomal recessive. E. crosses between true‑breeding white‑eyed females and white‑eyed males
B. crosses between true-breeding white‑eyed females and red‑eyed males
The platypus is a sexually reproducing mammal in which the sexes are separate. Unlike other mammals, the male has five X and five Y chromosomes. The female has 10 X chromosomes. Select the term that describes the organization of the sexual organs in the platypus. A. intersex B. dioecious C. hermaphroditic D. monoecious
B. dioecious
DNA sequencing has revealed the presence of which feature on the human Y chromosome? A. a higher density of genes than on other chromosomes B. eight large palindromes (sequences that read the same on both strands of DNA) C. the presence of extra copies of the SRY gene on autosomes D. many genes involved with female fertility
B. eight large palindromes (sequences that read the same on both strands of DNA)
Anhidrotic ectodermal dysplasia is an X‑linked recessive disorder in humans characterized by small teeth, no sweat glands, and sparse body hair. The trait is usually seen in men, but women who are heterozygous carriers of the trait often have irregular patches of skin with few or no sweat glands (see the illustration). Irregular patches of skin lacking sweat glands in heterozygous female carriers of anhidrotic ectodermal dysplasia are caused by: A. the presence of one X chromosome in some cells and the presence of two X chromosomes in other cells. B. inactivation of the X chromosome with the wild‑type allele in the cells of the sweat gland lacking patches. C. inactivation of the X chromosome with the dysplasia allele in the cells of the sweat gland lacking patches. D. nondisjunction of the X chromosome during gametogenesis in the cells of the sweat gland lacking patches. E. the presence of two X chromosomes in some cells and the presence of an X and a Y chromosome in other cells. Why does the distribution of the patches of skin lacking sweat glands differ among the females depicted in the illustration, even between the identical twins? A. It is due to the random determination of the number of Barr bodies in each cell. B. It is due to random mutations in the two twins. C. It is due to random inactivation of different X chromosomes in different cells. D. It is due to placement of sweat glands being affected by environmental factors. E. It is due to the pattern of sex determination being different in the two twins.
B. inactivation of the X chromosome with the wild‑type allele in the cells of the sweat gland lacking patches. C. It is due to random inactivation of different X chromosomes in different cells.
Males can inherit a gene for a sex-limited trait from their: A. mother's mother only. B. mother's or father's parents. C. father's mother only. D. mother's father only.
B. mother's or father's parents.
Martha has blood type AB. Where are the alleles for the A and B antigens located? A. on different, nonhomologous chromosomes B. on different homologous chromosomes C. on the same chromatid D. on sister chromatids
B. on different homologous chromosomes
In mammals, each inactivated X chromosome forms a darkly staining body known as a _____ body. Barr Lyon Morgan Bridges
Barr
Studies of rare white-eyed males in Drosophila crosses by _____ demonstrated that the gene for white eyes is on the X chromosome and confirmed the chromosome theory of inheritance. Mendel Bridges Barr Klinefelter
Bridges
The allele l in Drosophila is recessive, sex-linked, and lethal when homozygous or hemizygous (in males). There is no other phenotype associated with the mutant allele. If a female of genotype Ll is crossed with a normal male, what is the probability that the first two surviving flies will be males? A. 1/16 B. 1/2 C. 1/9 D. 1/32
C. 1/9
A normal female Drosophila produces abnormal eggs that contain a complete diploid set of her chromosomes. She mates with a normal male Drosophila that produces normal sperm. What will the sex ratio of the progeny from this cross be? A. all females B. 25% male, 50% intersex, 25% female C. 50% female, 50% intersex D. 50% males, 50% females E. 50% female, 50% metafemale
C. 50% female, 50% intersex
A gene has three alleles. How many different genotypes are possible at this locus in a diploid organism? A. 5 B. 3 C. 6 D. 7 E. 4
C. 6
Epistasis often results in modified dihybrid phenotypic ratios. Assume that you obtain one such modified ratio, 9:7, with the gene pairs A and B involved. What would be a possible genotype for a phenotype that would be included with the 9 portion of the modified ratio? A. aa bb B. aa Bb C. Aa BB D. aa BB E. Aa bb
C. Aa BB
In some reptilian species, temperature determines the sex of an embryo. The graph shows the effect of temperature on the percentage of male reptilian embryos, where Tp is the pivotal temperature. Select the statement that describes the influence of temperature on the percentage of male or female offspring as shown by the graph. A. Temperature only affects the percentage of male offspring, not female offspring. B. High temperatures do not affect sex. C. At high temperatures, nearly 100% of offspring will be male. D. At Tp, 100% of offspring will be male. E. At high temperatures, 0% are male offspring.
C. At high temperatures, nearly 100% of offspring will be male.
What does functional hemizygosity mean? A. The cells in an individual female are identical with respect to the expression of the genes on the X chromosome. B. In females that are heterozygous at an X-linked locus, all of the cells express one allele. C. The cells in an individual female are not identical with respect to the expression of the genes on the X chromosome. D. It refers to the degree of similarity of the alleles for a trait in an organism.
C. The cells in an individual female are not identical with respect to the expression of the genes on the X chromosome.
In what scenario would a human typically display male features? A. a defect in the SRY gene in an XX individual B. a defect in the receptor that binds testosterone in an XY individual C. a fragment of the Y chromosome containing the SRY gene attached to one X chromosome in an XX individual D. individuals with androgen-insensitivity syndrome (XX genotype)
C. a fragment of the Y chromosome containing the SRY gene attached to one X chromosome in an XX individual
In XX-XO sex determination, males have which sex chromosomes? A. two X chromosomes B. three X chromosomes C. a single X chromosome D. one X chromosome and one Y chromosome
C. a single X chromosome
In azaleas, the leaves and stems may be green, white, or variegated (mixture of green and white splotches). Female flowers from white plants were crossed using pollen from white plants, and the offspring were all white. If these same female flowers from white plants were crossed using pollen from green plants, what would be the phenotypic ratio in the offspring? A. 3 green : 1 white B. all variegated C. all white D. half green and half white
C. all white
Huntington's disease (HD) is an autosomal dominant condition that is typically not expressed until middle age. However, children receiving the mutant allele from their father often express the condition earlier in life. What term describes this situation? A. variable expressivity B. genomic imprinting C. anticipation D. reduced penetrance
C. anticipation
Which statement does not explain why tortoiseshell cats are usually female? A. because of X inactivation in females B. because the gene for the presence of orange color is on the X chromosome C. because cats have three copies of the X chromosome D. because males only have one copy of the X-linked locus for orange color
C. because cats have three copies of the X chromosome
Which of these is an example of dominant epistasis? A. seed shape and seed color in peas B. coat color in Labrador retrievers C. color in squash D. albinism in snails
C. color in squash
In Caenorhabditis elegans, the level of expression of genes on both X chromosomes of females is reduced by half. What phenomenon is this an example of? A. genomic imprinting B. extranuclear inheritance C. dosage compensation D. paternal mitochondrial leakage
C. dosage compensation
Fruit flies with XX sex chromosomes and three haploid sets of autosomes (AAA) have which sexual phenotype? A. male B. metamale C. intersex D. female
C. intersex
Sponges can produce sperm and eggs in a single organism. Which term describes the sex system of the organism? A. XY sex determination B. ZW sex determination C. monoecious D. XO sex determination E. dioecious
C. monoecious
The SRY gene in mammals is normally carried on which of these chromosomes? A. the Z chromosome B. both the X and the Y chromosomes C. the Y chromosome D. the X chromosome
C. the Y chromosome
A man, Joe, has classic hemophilia, an X‑linked recessive disease. Classify each person depending on whether or not Joe could have inherited the hemophilia gene from him or her. - Could have inherited? - Could not have inherited? Answer bank: - paternal grandfather - paternal grandmother - maternal grandfather - maternal grandmother
Could have inherited: - maternal grandfather - maternal grandmother Could not have inherited: - paternal grandfather - paternal grandmother
Dominant epistasis is seen in the interaction of two loci that determine fruit color in summer squash. When a homozygous plant that produces white squash is crossed with a homozygous plant that produces green squash and the F1 plants are crossed with each other, what is the resultant genotype ratio of the F2 generation? A. 9:7 B. 9:3:4 C. 9:3:3:1 D. 12:3:1
D. 12:3:1
If nondisjunction of X chromosomes occurs at a rate of 2% in a certain population of Drosophila, approximately how many white‑eyed males would you expect to see among 1000 offspring resulting from breeding a true‑breeding red‑eyed female with a white‑eyed male? A. 10 B. 2 C. This is impossible to calculate with the given information. D. 20 E. 5
D. 20
Because the white‑eye trait is X‑linked recessive, what result would you expect when crossing a heterozygous red‑eyed female with a red-eyed male? A. All females will be red‑eyed and all males will be white‑eyed. B. All offspring will be red-eyed. C. In both sexes, half of the offspring will have red eyes and half of the offspring will have white eyes. D. All females will have red eyes whereas half of the males will have red eyes and half will have white eyes. E. All males will be red-eyed whereas half of the females will have red eyes and half will have white eyes.
D. All females will have red eyes whereas half of the males will have red eyes and half will have white eyes.
Who was the scientist who first discovered darkly staining bodies in nuclei of cells from female cats which were later shown to be the inactive X chromosomes? A. Calvin Bridges B. Thomas Hunt Morgan C. Mary Lyon D. Murray Barr
D. Murray Barr
Two loci control body color in house flies. In a cross between a black fly and a gray fly, you obtain a 15:1 ratio, respectively. What kind of gene interaction is this? A. dominant and recessive B. epistasis C. duplicate recessive epistasis D. duplicate dominant epistasis E. recessive epistasis
D. duplicate dominant epistasis
The human genetic disease phenylketonuria (PKU) is caused by an autosomal recessive mutant allele. If left untreated, it leads to a high level of cognitive impairment due to toxic levels of phenylalanine. However, placing a child on a low-phenylalanine diet prevents the development of the intellectual disability. This situation is an example of which of these? A. a multifactorial characteristic B. a trait showing genetic maternal effects C. a temperature-sensitive allele that is active only at higher temperatures D. environmental effect on genotype expression
D. environmental effect on genotype expression
What type of gene action occurs when one gene masks the effect of another gene at a different locus? A. genomic imprinting B. anticipation C. complementation D. epistasis E. epigenetics
D. epistasis
What happens in the absence of testosterone and anti-Mullerian hormone? A. inactivation of an X chromosome B. degeneration of the female reproductive ducts C. male features develop D. female features develop
D. female features develop
Leber hereditary optic neuropathy (LHON) is a human disease that results from a mutation in the mitochondrial DNA. It is characterized by a rapid loss of vision in both eyes, resulting from the death of cells in the optic nerve. Assume that an affected man marries an unaffected woman. What proportion of their children is going to be affected with LHON? A. one-half B. one-fourth C. all D. none
D. none
In a __________, environmental factors alone can produce a phenotype that is the same as the phenotype produced by a genotype. A. compound heterozygote B. genetic maternal effect C. polygenic characteristic D. phenocopy E. pleiotropy
D. phenocopy
In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only. Two heterozygous birds are mated. What fraction of the offspring is expected to exhibit hen feathering? A. one-fourth B. all C. three-fourths D. seven-eighths
D. seven-eighths
A recessive mutant allele of an autosome gene in a species of mouse results in a shorted tail in males when homozygous. However, when homozygous in females, this genotype has no effect, and the mice have normal tails. What is this genetic phenomenon called? A. genomic imprinting B. cytoplasmic inheritance C. genetic maternal effect D. sex‑limited characteristic E. sex‑influenced characteristic
D. sex‑limited characteristic
Multifactorial characteristics result from which of the statements? A. the activity of a gene locus where there are multiple alleles B. temperature‑sensitive alleles that are showing epigenetic expression C. complementation between mutant alleles in different genes D. the activity of polygenes influenced by environmental factors E. the activity of compound heterozygotes
D. the activity of polygenes influenced by environmental factors
With genetic maternal effect, the phenotype of an individual is determined by which of the statements? A. the sex of the individual with only one sex able to express the genotype B. cytoplasmic genes usually located in the mitochondria C. a combination of environmental factors and the genotype of the individual D. the nuclear genotype of the maternal parent E. the sex of the parent who transmits the gene to the individual
D. the nuclear genotype of the maternal parent
In chickens, the dominant allele Cr produces the creeper phenotype (having extremely short legs). However, the creeper allele is lethal in the homozygous condition. The homozygous recessive genotype results in a normal individual. If two creepers are mated, what will be the phenotypic ratio among the living offspring? A. 1 normal : 1 creeper B. 3 creepers : 1 normal C. 3 normal : 1 creeper D. 2 normal : 1 creeper E. 2 creepers : 1 normal
E. 2 creepers : 1 normal
If the white‑eye trait were Y‑linked dominant, rather than X‑linked recessive, what result would you expect when crossing a red‑eyed female with a white‑eyed male? A. All offspring will be red‑eyed. B. All female offspring will be white‑eyed, whereas half of the male offspring will have white eyes and half of the male offspring will have red eyes. C. All male offspring will be red‑eyed male, whereas half of the female offspring will have white eyes and half of the female offspring will have red eyes. D. For each sex, half of the offspring will have red eyes and half of the offspring will have white eyes. E. All female offspring will be red‑eyed and all male offspring will be white‑eyed.
E. All female offspring will be red‑eyed and all male offspring will be white‑eyed.
If the white-eye trait were X‑linked dominant, rather than X‑linked recessive, what result would you expect when crossing a heterozygous white‑eyed female with a white‑eyed male? A. All offspring will be red‑eyed. B. All male offspring will be red‑eyed, whereas half of the female offspring will have white eyes and half of the female offspring will have red eyes. C. For each sex, half of the offspring will have red eyes and half of the offspring will have white eyes. D. All female offspring will be red‑eyed, whereas half of the male offspring will have white eyes and half of the male offspring will have red eyes. E. All female offspring will be white-eyed, where as half of the male offspring will have white eyes and half of the male offspring will have red eyes.
E. All female offspring will be white-eyed, where as half of the male offspring will have white eyes and half of the male offspring will have red eyes.
If the white‑eye trait were X‑linked dominant rather than X‑linked recessive, what result would you expect when crossing a heterozygous white‑eyed female with a red‑eyed male? A. All female offspring will be red‑eyed, whereas half of the male offspring will have white eyes and half of the male offspring will have red eyes. B. All female offspring will be red‑eyed and all male offspring will be white‑eyed. C. All offspring will be red‑eyed. D. All male offspring will be red‑eyed, whereas half of the female offspring will have white eyes and half of the female offspring will have red eyes. E. For each sex, half of the offspring will have red eyes and half of the offspring will have white eyes.
E. For each sex, half of the offspring will have red eyes and half of the offspring will have white eyes.
A man and a woman are both deaf due to being homozygous for a recessive autosomal mutant allele. However, they are homozygous recessive at different gene loci. If all their children have normal hearing, which event has occurred within each child? A. incomplete dominance B. epistasis C. gene interaction D. codominance E. complementation
E. complementation
In humans, mitochondrial genetic disorders are inherited from only the mother. The severity of such diseases can vary greatly, even within a single family. What form of inheritance does this represent? A. sex‑limited inheritance B. sex‑influenced inheritance C. genomic imprinting D. genetic maternal effect E. cytoplasmic inheritance
E. cytoplasmic inheritance
A gene whose expression is affected by the sex of the transmitting parent demonstrates which of the events? A. epigenetics B. anticipation C. pleiotropy D. genetic maternal effect E. genomic imprinting
E. genomic imprinting
What is penetrance? A. a situation where an allele is only expressed in one sex and does not produce the same phenotype in the other sex B. a situation where the stronger or earlier expression of a genetic trait occurs in succeeding generations C. the degree to which a trait is expressed D. a situation where a trait is only expressed at a particular temperature E. the percentage of individuals having a particular genotype who express the expected phenotype
E. the percentage of individuals having a particular genotype who express the expected phenotype
Miniature wings, Xm, in Drosophila melanogaster result from an X‑linked allele that is recessive to the allele for long wings, X+. Match the genotypes for each parent in the crosses. - Male Parent Genotype? - Female parent genotype?
Male Parent Genotype: - X+Y, XmY, XmY, X+Y, X+Y Female parent genotype: - X+Xm, X+X+, X+Xm, XmXm, X+X+
An antigen found on red blood cells, Xg, is encoded by an X‑linked allele (𝑋𝑎) that is dominant over an allele for the absence of the antigen (𝑋−). Scientists studied the inheritance of these X‑linked alleles in children with chromosome abnormalities to determine where nondisjunction of the sex chromosomes occurred. Match the genotypes of the parents and offspring to the parent and cell division stage in which the nondisjunction must have occurred. Shown as parent×parent=child. - Nondisjunction in the mother during meiosis I or II? - Nondisjunction in the father during meiosis I or II? - Nondisjunction in the father during meiosis I? - Nondisjunction in the mother during meiosis II?
Nondisjunction in the mother during meiosis I or II: - X^aY x X^-X^- = X^a Nondisjunction in the father during meiosis I or II: - X^aY x X^aX^- = X^- Nondisjunction in the father during meiosis I: - X^aY x X^-X^- = X^aX^-Y Nondisjunction in the mother during meiosis II: - X^aY x X^aX^- = X^-X^-Y
Coat color in cats is determined by genes at several different loci. At one locus on the X chromosome, one allele (X^+) encodes black fur and another allele (X^o) encodes orange fur. Females can be black (X^+X^+), orange (X^oX^o), or a mixture of orange and black called tortoiseshell (X^+X^o). Males are either black (X^+Y) or orange (X^oY). Bill has a female tortoiseshell cat named Patches. One night, Patches escapes from Bill's house, spends the night out, and mates with a stray male. Patches later gives birth to the following kittens: one orange male, one black male, two tortoiseshell females, and one orange female. What are the genotypes of Patches, the stray male, and the kittens? - Patches? - Stray Male? - Orange Male Kitten? - Black Male Kitten? - Tortoiseshell Female Kitten? - Orange Female Kitten? Answer bank: - X^oY - X^+X^+ - X^+Y - X^oX^o - X^+X^o
Patches: - X^+X^o Stray Male: - X^oY Orange Male Kitten: - X^oY Black Male Kitten: - X^+Y Tortoiseshell Female Kitten: - X^+X^o Orange Female Kitten: - X^oX^o
Classify whether each gene regularly exists in a hemizygous state. - Regularly hemizygous? - Not regularly hemizygous? Answer bank: - a color-blindness gene on the X chromosome in a normal human male - a transgenic gene inserted into only one chromosome of a mouse - a gene on chromosome 21 in an individual with Down syndrome - a color-blindness gene on an X chromosome in a normal human female
Regularly hemizygous: - a color-blindness gene on the X chromosome in a normal human male - a transgenic gene inserted into only one chromosome of a mouse Not regularly hemizygous: - a gene on chromosome 21 in an individual with Down syndrome - a color-blindness gene on an X chromosome in a normal human female
In Drosophila melanogaster, white eye is an X‑linked recessive trait, and red eye is an X‑linked dominant trait. Assume that the flies have a diploid set of autosomes (2A). Allele Xw codes for white eye, and allele X codes for red eye. Match each of the genotypes with the expected sex and eye color. Sex/Eye color? - XX? - X[^W]X? - X [^W]Y? - XO? - X[^W]XY? - X[^W]X[^W]X? Answer bank: - female - male - metafemale - white - red
XX: - female - red X[^W]X: - female - red X [^W]Y: - male - white XO: - male - red X[^W]XY: - female - red X[^W]X[^W]X: - metafemale - red
Suppose the ear length of two populations of jerboas is controlled by one gene. To determine the mode of inheritance, a homozygous short‑eared female is crossed with a homozygous long‑eared male. Then, siblings from the F1 are crossed, and the number of short‑ and long‑eared animals are counted to determine the phenotype ratio. Match the phenotypic ratio anticipated in the offspring from a cross of two heterozygous individuals to the appropriate mode of inheritance for the short‑ear allele. Chart layout: [Mode of inheritance; Autosomal dominant; Autosomal recessive; Sex-linked dominant; Sex-linked recessive] [F1 phenotype; All short-eared; All long-eared; All short-eared; Long-eared females, short-eared males] [Cross of heterozygotes; *______, ______, _______, _______ ]*? Answer bank: - male 1 long : 1 short; females all short - 1 long : 3 short - 1 long : 1 short - 3 long : 1 short
[Cross of heterozygotes; *1 long : 3 short; 3 long : 1 short; males 1 long : 1 short; females all short; 1 long : 1 short]*
Match the sexual phenotype of fruit flies that have the listed chromosomes. Chart layout: [Sex chromosomes; Autosomal chromosomes; Sexual phenotype] [XX; all normal; *________* ] [XY; all normal; *________* ] [XO; all normal; *_______* ] [XXY; all normal; *_______* ] [XYY; all normal; *_______* ] [XXYY; all normal; *_______* ] [XXX; all normal; *________* ] [XX; 4 haploid sets; *_______ *] [XXX; 4 haploid sets; *________* ] [XXX; 3 haploid sets; *________* ] [X; 3 haploid sets; *_______* ] [XY; 3 haploid sets; *______* ] [XX; 3 haploid sets; *______* ] Answer bank: - metafemale - sterile male - intersex - male - female - sterile metamale - metamale
[XX; all normal; *female*] [XY; all normal; *male*] [XO; all normal; *sterile male*] [XXY; all normal; *female*] [XYY; all normal; *male*] [XXYY; all normal; *female*] [XXX; all normal; *metafemale*] [XX; 4 haploid sets; *sterile male*] [XXX; 4 haploid sets; *intersex*] [XXX; 3 haploid sets; *female*] [X; 3 haploid sets; *sterile metamale*] [XY; 3 haploid sets; *metamale*] [XX; 3 haploid sets; *intersex*]
The sex that produces two different types of gametes with respect to the sex chromosomes is called the _____ sex. dioecious monoecious pseudoautosomal heterogametic
heterogametic
Traits encoded by genes located on the Y chromosome are termed Y-_____ traits. disjoined labeled dissociated linked
linked
In biology, the sex (male or female) of an organism is defined in reference to its _____. presence or absence of a Y chromosome phenotype genotype presence or absence of two X chromosomes
phenotype
