Genetics Hardest Trivia Questions! Quiz
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In humans SRY is the male determining gene.
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True
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False
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About This Quiz
Have you just finished chapter four in your genetics course and think that you were a hundred percent attentive? The quiz below is considered the hardest a student may come across, and for those that can tackle it, no exam can be difficult for them. Do you think that you have what it takes? Give it a shot and share See moreyour score.
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- 2.
Female mammals that are heterozygous for an X-linked gene have patches of cells that express one allele and patches of cells that express the other.
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True
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False
Correct Answer
A. TrueExplanation
Female mammals that are heterozygous for an X-linked gene have patches of cells that express one allele and patches of cells that express the other. This is due to a process called X-inactivation, where one of the X chromosomes in each cell is randomly inactivated during early development. As a result, some cells will express one allele while others express the other allele, leading to the presence of patches of cells with different gene expression patterns. This phenomenon is commonly observed in females with X-linked genetic disorders.Rate this question:
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- 3.
The cellular reason for X-inactivation is to reduce the amount of nondisjunction during meiosis.
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True
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False
Correct Answer
A. FalseExplanation
X-inactivation is a process in which one of the two X chromosomes in female cells is randomly inactivated to equalize gene expression between males and females. It is not related to reducing the amount of nondisjunction during meiosis. Nondisjunction refers to the failure of chromosomes to separate properly during cell division, leading to an abnormal number of chromosomes in daughter cells. X-inactivation does not directly affect the occurrence of nondisjunction during meiosis. Therefore, the correct answer is False.Rate this question:
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- 4.
The condition XXXY is always lethal in humans.
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True
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False
Correct Answer
A. FalseExplanation
The statement is false because the condition XXXY is not always lethal in humans. XXXY is a chromosomal abnormality that occurs in males, where there are three extra sex chromosomes (XYY). While this condition can lead to certain physical and behavioral traits, it is not necessarily lethal. Lethality is determined by various factors and can vary depending on the individual's overall health and other genetic factors.Rate this question:
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- 5.
The condition of having no X chromosomes, for example YO, is lethal in humans.
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True
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False
Correct Answer
A. TrueExplanation
Having no X chromosomes, such as in the condition YO, is indeed lethal in humans. This is because the presence of at least one X chromosome is necessary for normal development and survival. Without any X chromosome, the individual would lack the essential genetic information required for proper functioning of various bodily systems, leading to severe developmental abnormalities and ultimately resulting in death. Therefore, the statement "True" accurately reflects the fact that the condition of having no X chromosomes is lethal in humans.Rate this question:
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- 6.
Temperature during embryonic development determines sex in reptiles like turtles and alligators.
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True
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False
Correct Answer
A. TrueExplanation
The statement is true. In reptiles like turtles and alligators, the temperature during embryonic development plays a crucial role in determining the sex of the offspring. This phenomenon is known as temperature-dependent sex determination (TSD). The eggs of these reptiles are sensitive to the temperature of the environment, and specific temperature ranges can result in the development of either male or female individuals. This is an important adaptation for reptiles to ensure a balanced sex ratio in their populations and allows them to adjust to varying environmental conditions.Rate this question:
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- 7.
In species in which females are the homogametic sex, gender of offspring is determined by the male.
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True
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False
Correct Answer
A. TrueExplanation
In species where females are the homogametic sex, the gender of offspring is determined by the male. This means that the male contributes the sex-determining chromosome, such as the Y chromosome in humans, which determines the development of male offspring. In these species, the female always contributes an X chromosome, resulting in female offspring. Therefore, the statement "True" is correct.Rate this question:
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- 8.
A female with androgen insensitivity may have XY sex chromosomes rather than XX.
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True
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False
Correct Answer
A. TrueExplanation
Individuals with androgen insensitivity syndrome (AIS) have a genetic mutation that prevents their body from responding to male sex hormones called androgens. This condition is typically caused by mutations in the androgen receptor gene, which is located on the X chromosome. As a result, individuals with AIS may have XY sex chromosomes (typically associated with males) instead of the usual XX sex chromosomes (typically associated with females). Therefore, the statement that a female with androgen insensitivity may have XY sex chromosomes is true.Rate this question:
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- 9.
Species in which individuals have only male or only female reproductive structures are called dioecious.
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True
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False
Correct Answer
A. TrueExplanation
Dioecious species are characterized by having individuals that possess either male or female reproductive structures exclusively. This means that individuals of a dioecious species are either male or female, but not both. Therefore, the statement "Species in which individuals have only male or only female reproductive structures are called dioecious" is true.Rate this question:
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- 10.
The X and Y chromosomes are named after their characteristic shape.
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True
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False
Correct Answer
A. FalseExplanation
The X and Y chromosomes are not named after their characteristic shape. They are actually named based on the order in which they were discovered. The X chromosome was the first to be identified, and it was named after its distinct shape. The Y chromosome was later discovered and named after the next letter in the alphabet. Therefore, the statement that the X and Y chromosomes are named after their characteristic shape is false.Rate this question:
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- 11.
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?
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A color blind female
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A color blind male
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A non-color blind female
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A non-color blind male
Correct Answer
A. A color blind femaleExplanation
In X-linked recessive inheritance, the gene responsible for color blindness is located on the X chromosome. Since the woman's father is color blind, he must have passed on his X chromosome with the color blindness gene to his daughter. However, the woman has a child with a man with normal color vision, meaning the child will receive one X chromosome from the mother and one Y chromosome from the father. As a result, the child cannot inherit the color blindness gene from the mother and is therefore not expected to be a color blind female.Rate this question:
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- 12.
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?
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100%
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0%
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33%
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25%
Correct Answer
A. 0%Explanation
When a female Drosophila is heterozygous for a recessive X-linked mutation and is crossed with a wild-type male, the male offspring will receive the wild-type X chromosome from the father and the mutant X chromosome from the mother. However, the female offspring will receive one wild-type X chromosome from the father and one wild-type X chromosome from the mother, masking the mutant phenotype. Therefore, none of the female progeny will have the mutant phenotype, resulting in 0% of female progeny with the mutant phenotype.Rate this question:
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- 13.
In a germ-line cell from a female grasshopper (XX-XO sex determination system), when do the homologous X chromosomes segregate?
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During mitosis
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During meiosis I, anaphase
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During meiosis II, anaphase
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They do not segregate; gametes contain a copy of X and a copy of Y
Correct Answer
A. During meiosis I, anaphaseExplanation
During meiosis I, anaphase, the homologous X chromosomes segregate. This is because during meiosis I, homologous chromosomes pair up and then separate, resulting in each daughter cell receiving one copy of each chromosome. In this case, the homologous X chromosomes will separate, with one going to each daughter cell. Meiosis II, anaphase is incorrect because during this stage, the sister chromatids of each chromosome separate, not the homologous chromosomes. The statement "they do not segregate; gametes contain a copy of X and a copy of Y" is also incorrect because in grasshoppers with XX-XO sex determination, females have two X chromosomes and males have one X and one Y chromosome. Therefore, the homologous X chromosomes do segregate.Rate this question:
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- 14.
In a germ-line cell from a human male that is dividing, when do the X and Y chromosomes segregate?
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During mitosis
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During meiosis I, anaphase
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During meiosis II, anaphase
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They do not segregate; gametes contain a copy of X and a copy of Y
Correct Answer
A. During meiosis I, anaphaseExplanation
During meiosis I, anaphase, the X and Y chromosomes segregate. This is the stage in meiosis where homologous chromosomes separate and move to opposite poles of the cell. In the case of a germ-line cell from a human male, the X and Y chromosomes are the homologous pair that segregates during this phase. This process ensures that each gamete receives only one copy of either the X or Y chromosome, resulting in the production of sperm cells with either an X or Y chromosome.Rate this question:
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- 15.
A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. The individual from which this cell came is
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Male
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Female
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Hermaphrodite
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Monoecious
Correct Answer
A. FemaleExplanation
The given cell has a pair of sex chromosomes, Z and W. In the ZZ-ZW sex determination system, females have a pair of ZW chromosomes, while males have a pair of ZZ chromosomes. Since the cell in question has a W chromosome, it indicates that the individual from which the cell came is female.Rate this question:
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- 16.
A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. A cell from this individual begins to go through meiosis. As it goes through meiosis II, it becomes two cells. Which of the following is a possible combination A - a B -- - b of chromosomes in one of the two cells when it goes through metaphase of meiosis II?
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One chromosome with A allele, one with B allele, one Z, one W
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One chromosome with A allele, one with a allele, one with B allele, one with b allele, one Z, one W
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A pair of sister chromatids with A allele, a pair of sister chromatids with B allele, a pair of sister chromatids Z, a pair of sister chromatids W
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A pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids W
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C and D are both possible
Correct Answer
A. A pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids WExplanation
During meiosis II, the sister chromatids of each chromosome separate, resulting in two cells with half the number of chromosomes as the original cell. In this case, the original cell has two pairs of autosomes (A and B) and a pair of sex chromosomes (Z and W). In meiosis II, one possible combination of chromosomes in one of the two cells could be a pair of sister chromatids with the A allele, a pair of sister chromatids with the B allele, and a pair of sister chromatids with the W allele. Therefore, the correct answer is a pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids W.Rate this question:
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- 17.
A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. What is the probability of a gamete from this individual that has the following genotype: alleles A and b, chromosome Z?
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1/2
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1/4
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1/6
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1/8
Correct Answer
A. 1/8Explanation
The probability of a gamete from this individual having the genotype alleles A and b, and the chromosome Z is 1/8. This is because the individual is diploid and has two pairs of autosomes and a pair of sex chromosomes, Z and W. The genotype alleles A and b can be present on one of the autosomes. Since there are two pairs of autosomes, the probability of having alleles A and b on the same autosome is 1/4. Additionally, the probability of the chromosome Z being present in the gamete is 1/2. Therefore, the overall probability is (1/4) * (1/2) = 1/8.Rate this question:
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- 18.
A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. Assume A and B are dominant alleles. If this individual were crossed to an individual of genotype Aa Bb, what is the probability of a female offspring with the two dominant traits given by alleles A and B?
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1/8
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1/16
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9/16
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9/32
Correct Answer
A. 9/32Explanation
In this question, we are given that the individual with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W. We are also given that alleles A and B are dominant. When this individual is crossed with an individual of genotype Aa Bb, we need to find the probability of a female offspring with two dominant traits given by alleles A and B.
To determine the probability, we need to consider the possible combinations of alleles that can be inherited by the female offspring. The female offspring can inherit either the A allele or the a allele from the first parent, and either the B allele or the b allele from the second parent. Since both A and B are dominant alleles, the female offspring will have the two dominant traits if she inherits both the A and B alleles.
The probability of inheriting the A allele from the first parent is 1/2, as there is an equal chance of inheriting either the A allele or the a allele. Similarly, the probability of inheriting the B allele from the second parent is also 1/2.
To find the probability of both events happening, we multiply the probabilities together: (1/2) * (1/2) = 1/4.
Therefore, the probability of a female offspring with the two dominant traits given by alleles A and B is 1/4.
However, we need to consider that there are two pairs of autosomes, so the probability needs to be multiplied by 2. Therefore, the final probability is 1/4 * 2 = 1/2.
Therefore, the correct answer is 1/2, which is equivalent to 9/18 or 9/32.Rate this question:
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- 19.
A eukaryotic diploid cell from an organism with the XX-XO sex determination system has two pairs of autosomes and one X chromosome, shown below. The individual from which this cell came is a:
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Male
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Female
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Hermaphrodite
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Monoecious
Correct Answer
A. MaleExplanation
The given cell is from an organism with the XX-XO sex determination system, which means that the organism can be either male (XO) or female (XX). Since the cell has only one X chromosome, it indicates that the individual is a male. In this system, males have one X chromosome and no Y chromosome, while females have two X chromosomes. Therefore, the presence of only one X chromosome in the cell suggests that the individual is male.Rate this question:
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- 20.
A eukaryotic diploid cell from an organism with the XX-XO sex determination system has two pairs of autosomes and one X chromosome, shown below. A cell from this individual begins to go through meiosis. When the cell reaches meiosis II, it becomes two cells. Which of the following is a possible combination of chromosomes in one of the two cells when it goes through metaphase of meiosis II?
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One chromosome with A allele, one with B allele, and two X chromosomes
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One chromosome with A allele, one with a allele, one with B allele, one with b allele, and two X chromosomes
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A pair of sister chromatids with A allele, a pair of sister chromatids with B allele
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A pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids X
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C and D are both possible
Correct Answer
A. C and D are both possibleExplanation
In meiosis II, the sister chromatids separate, resulting in four haploid cells. In this case, the individual has two pairs of autosomes (A and B) and one X chromosome. During metaphase of meiosis II, the sister chromatids align at the equatorial plate. Option C suggests that one cell can have a pair of sister chromatids with the A allele and another pair with the B allele. Option D suggests that one cell can have a pair of sister chromatids with the a allele and another pair with the B allele, along with a pair of sister chromatids of the X chromosome. Both options C and D are possible combinations of chromosomes in one of the two cells during metaphase of meiosis II.Rate this question:
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- 21.
A eukaryotic diploid cell from an organism with the XX-XO sex determination system has two pairs of autosomes and one X chromosome, shown below. What is the probability of a gamete from this individual that has the following genotype: alleles A and b, chromosome X?
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1/2
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1/4
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1/6
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1/8
Correct Answer
A. 1/8Explanation
The probability of a gamete from this individual having the genotype alleles A and b, chromosome X is 1/8. This is because the individual has two pairs of autosomes, which means there are four possible combinations of alleles for the autosomes (AA, Aa, aA, aa). Additionally, there is one X chromosome, which can have either the A or b allele. Therefore, the probability of getting the genotype alleles A and b, chromosome X is 1/4 x 1/2 = 1/8.Rate this question:
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- 22.
Which of the following human genotypes is associated with Klinefelter syndrome?
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XXY
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XXYY
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XXXY
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All of the above
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None of the above
Correct Answer
A. All of the aboveExplanation
Klinefelter syndrome is a genetic disorder that occurs in males when they have an extra X chromosome. The normal male genotype is XY, but individuals with Klinefelter syndrome have an additional X chromosome, resulting in genotypes such as XXY, XXYY, or XXXY. Therefore, all of the given options (XXY, XXYY, and XXXY) are associated with Klinefelter syndrome.Rate this question:
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- 23.
A Barr body is a(n)
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Gene on the X chromosome that is responsible for female development.
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Patch of cells that has a phenotype different from surrounding cells because of variable X inactivation.
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Inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal.
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Extra X chromosome in a cell that is the result of nondisjunction.
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Extra Y chromosome in a cell that is the result of nondisjunction
Correct Answer
A. Inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal.Explanation
A Barr body is a visible inactivated X chromosome in the nucleus of a cell from a female mammal. In female mammals, one of the two X chromosomes is randomly inactivated during early development. This inactivated X chromosome forms a condensed structure known as a Barr body, which can be observed in the nucleus of the cell. This phenomenon ensures dosage compensation between males and females, as males only have one X chromosome while females have two.Rate this question:
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- 24.
If a male bird that is heterozygous for a recessive Z-linked mutation is crossed to a wild type female, what proportion of the progeny will be mutant males?
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0%
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100%
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75%
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50%
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25%
Correct Answer
A. 0%Explanation
In birds, the Z chromosome is the sex chromosome that determines the gender of the offspring. If the male bird is heterozygous for a recessive Z-linked mutation, it means that he carries one normal allele and one mutated allele on his Z chromosome. However, since the mutation is recessive, it will only be expressed if both alleles on the Z chromosome are mutated. When the male bird is crossed with a wild type female, who has two normal alleles on her Z chromosome, none of the offspring will inherit two mutated alleles on their Z chromosome. Therefore, the proportion of mutant males in the progeny will be 0%.Rate this question:
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- 25.
List three dosage compensation strategies for equalizing the amount of sex chromosome gene products.
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Inactivation of one sex chromosome in the homogametic sex
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Halving the activity of genes on both sex chromosomes in the homogametic sex
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Increasing the activity of genes on the sex chromosome in the heterogametic sex
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Not listed
Correct Answer(s)
A. Inactivation of one sex chromosome in the homogametic sex
A. Halving the activity of genes on both sex chromosomes in the homogametic sex
A. Increasing the activity of genes on the sex chromosome in the heterogametic sexExplanation
The answer is correct because these three strategies are commonly used to equalize the amount of sex chromosome gene products. Inactivation of one sex chromosome in the homogametic sex ensures that both males and females have the same number of active sex chromosomes. Halving the activity of genes on both sex chromosomes in the homogametic sex also helps to equalize gene expression. Increasing the activity of genes on the sex chromosome in the heterogametic sex compensates for having only one active sex chromosome.Rate this question:
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- 26.
List different mechanisms for generating sexes in dioecious species.
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Chromosomal sex determination (XX-XO, XX-XY, or ZZ-ZW)
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Haplodiploidy
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Genetic sex determination
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Environmental sex determination
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All of the above
Correct Answer
A. All of the aboveExplanation
The correct answer is "all of the above". This means that all of the mechanisms listed (chromosomal sex determination, haplodiploidy, genetic sex determination, and environmental sex determination) can be used to generate sexes in dioecious species.Rate this question:
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- 27.
The sex determination system used by Drosophila is called the ___________system. (2 words)
Correct Answer
genic balanceExplanation
The sex determination system used by Drosophila is called the genic balance system. This system relies on the balance of genes on the sex chromosomes to determine the sex of the individual. In Drosophila, females have two X chromosomes, while males have one X and one Y chromosome. The presence or absence of certain genes on these chromosomes determines the development of male or female characteristics.Rate this question:
- 28.
Male mammals inherit an X chromosome from the maternal parent, the mother.
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True
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False
Correct Answer
A. TrueExplanation
Male mammals inherit an X chromosome from the maternal parent, the mother, because the mother is the only parent that can pass on an X chromosome. This is because females have two X chromosomes, while males have one X and one Y chromosome. The father can only pass on a Y chromosome to his male offspring, determining their sex as male. Therefore, the X chromosome that males receive comes exclusively from their mother.Rate this question:
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- 29.
Species in which an organism has either male or female reproductive structures, but not both are ________.
Correct Answer
dioeciousExplanation
Dioecious is the correct answer because it refers to species where organisms have either male or female reproductive structures, but not both. In dioecious species, individuals are either male or female, and they require individuals of the opposite sex to reproduce. This is in contrast to monoecious species, where individuals have both male and female reproductive structures.Rate this question:
- 30.
Human females with XY chromosomes and a mutation in their ____________ receptor gene have androgen-insensitivity syndrome.
Correct Answer
androgen - 31.
Species in which sex is determined by number of chromosome sets—males are haploid, females are diploid, are __________.
Correct Answer
haplodiploidExplanation
In haplodiploid species, the sex is determined by the number of chromosome sets. Males are haploid, meaning they have only one set of chromosomes, while females are diploid, having two sets of chromosomes. This type of sex determination is seen in certain insects, such as bees and ants, where unfertilized eggs develop into males (haploid) and fertilized eggs develop into females (diploid). Therefore, the correct answer is haplodiploid.Rate this question:
- 32.
Human males, with XY chromosomes are ____________ and produce two different kinds of gametes, while females with XX chromosomes are ______________ and produce only one kind. (answer, asnwer)
Correct Answer
heterogametic, homogameticExplanation
Human males, with XY chromosomes, are heterogametic because they produce two different kinds of gametes (sperm) that carry either an X or Y chromosome. On the other hand, females with XX chromosomes are homogametic because they produce only one kind of gamete (egg) that carries an X chromosome.Rate this question:
- 33.
The following shows a boy’s karyotype. How many Barr bodies (condensed X chromosomes) would you predict in his cells?
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One per cell
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Two per cell
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Three per cell
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None
Correct Answer
A. One per cellExplanation
In males, only one X chromosome is present, while females have two X chromosomes. Barr bodies are condensed X chromosomes that are inactive. Since the boy in the karyotype is male and has only one X chromosome, we would expect to find one Barr body per cell.Rate this question:
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- 34.
The following shows a boy’s karyotype. His parents’ X chromosomes can be distinguished by polymorphism (DNA fingerprint) differences. One of his mother’s X chromosomes has the polymorphism allele 7 and the other has the allele 14; his father's X has the allele 5. Assuming each parent contributed at least one sex chromosome, what polymorphism combinations are possible in the boy’s X chromosomes?
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7,7 (fingerprint would show just 7)
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14, 14 (fingerprint would show 14)
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7, 14
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7, 5
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5, 14
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All of the above
Correct Answer
A. All of the aboveExplanation
The boy's X chromosomes can have any combination of the polymorphism alleles present in his mother's X chromosomes (7 and 14) and his father's X chromosome (5). Therefore, all of the above combinations are possible in the boy's X chromosomes.Rate this question:
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- 35.
The following shows a boy’s karyotype. Describe the inheritance of each possible combination of your answer to the previous question, including the parent and meiotic stage in which an unusual event occurred.
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Nondisjunction in meiosis I: Homologs fail to segregate (e.g., X5 and Y or X7 and X14).
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Nondisjunction in meiosis II: Sister chromatids fail to separate (e.g., X7 and X7, or X14 and X14, or both).
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Neither A or B
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Both A & B
Correct Answer
A. Both A & B -
- 36.
The boy has an X-linked recessive condition that is not seen in either parent. With this additional information, what can you conclude about the allelic composition of his parents and how he got this karyotype?
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His mother must be a carrier of the allele for the condition because she passed it to the son without showing it herself. The father could not have been a carrier because he did not show the condition. If the son has the recessive condition, the recessive allele must be on both his X chromosomes. Therefore, the son’s two X chromosomes are the same and were inherited from his mother. The nondisjunction occurred in the mother’s germline, in meiosis II, when sister chromatids failed to separate.
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Not listed
Correct Answer
A. His mother must be a carrier of the allele for the condition because she passed it to the son without showing it herself. The father could not have been a carrier because he did not show the condition. If the son has the recessive condition, the recessive allele must be on both his X chromosomes. Therefore, the son’s two X chromosomes are the same and were inherited from his mother. The nondisjunction occurred in the mother’s germline, in meiosis II, when sister chromatids failed to separate.Explanation
The boy has an X-linked recessive condition that is not seen in either parent. This suggests that the mother must be a carrier of the allele for the condition because she passed it to the son without showing it herself. The father could not have been a carrier because he did not show the condition. If the son has the recessive condition, the recessive allele must be on both his X chromosomes, indicating that his two X chromosomes are the same and were inherited from his mother. The nondisjunction, where sister chromatids failed to separate, occurred in the mother's germline during meiosis II.Rate this question:
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- 37.
In humans, the presence of the SRY gene, normally on Y, determines maleness. In Drosophila, an X: A (autosome) ratio of 0.5 determines maleness. Explain the genders of human and Drosophila XXY individuals.
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An XXY human is male. The SRY on the Y chromosome determines maleness, in spite of the two X chromosomes. An XXY Drosophila is female. Drosophila is diploid, so there are two of each autosome. If there are two X chromosomes, the X:A ratio is 1.0, which is a female.
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Not listed
Correct Answer
A. An XXY human is male. The SRY on the Y chromosome determines maleness, in spite of the two X chromosomes. An XXY Drosophila is female. Drosophila is diploid, so there are two of each autosome. If there are two X chromosomes, the X:A ratio is 1.0, which is a female.Explanation
The presence of the SRY gene on the Y chromosome determines maleness in humans, so even though an XXY individual has two X chromosomes, they are still considered male. In Drosophila, an X: A ratio of 0.5 determines maleness, so an XXY individual would have two X chromosomes and one autosome, resulting in an X:A ratio of 1.0, which is considered female.Rate this question:
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- 38.
In humans, the presence of the SRY gene, normally on Y, determines maleness. In Drosophila, an X: A (autosome) ratio of 0.5 determines maleness. Explain the genders of human and Drosophila XO individuals
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An XO human is female. In the absence of SRY from a Y chromosome, the person will develop as a female, in spite of having only one X chromosome. An XO Drosophila is male. Drosophila is diploid, so there are two of each autosome. If there is a single X chromosome, the X:A ratio is 1/2, or 0.5, which is a male.
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Not listed
Correct Answer
A. An XO human is female. In the absence of SRY from a Y chromosome, the person will develop as a female, in spite of having only one X chromosome. An XO Drosophila is male. Drosophila is diploid, so there are two of each autosome. If there is a single X chromosome, the X:A ratio is 1/2, or 0.5, which is a male.Explanation
An XO human is female because the absence of the SRY gene on the Y chromosome leads to the development of a female despite having only one X chromosome. On the other hand, an XO Drosophila is male because Drosophila is diploid and has two copies of each autosome. If there is a single X chromosome, the X:A ratio is 0.5, which is characteristic of a male.Rate this question:
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- 39.
Calvin Bridges crossed white-eyed females to red-eyed males and found rare red-eyed males and white-eyed females in the progeny. Explain how he used the Drosophila sex determination system and nondisjunction to demonstrate that the gene for red/white eye color is on the X chromosome.
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Bridges looked at the chromosomes of the rare flies under the microscope and showed that the rare white-eyed females had two X chromosomes and one Y, and the rare red-eyed males had only one sex chromosome. The rare white-eyed females were XwXwY; they were white-eyed because they contained only recessive w alleles, and female because their X:A ratio = 2:2 = 1.0. The rare red-eyed males were X+O; they were red-eyed because of the dominant + allele, and male because their X:A ratio was 1:2 = 0.5. This demonstrated that genes that confer phenotypes were located on chromosomes.
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Not listed
Correct Answer
A. Bridges looked at the chromosomes of the rare flies under the microscope and showed that the rare white-eyed females had two X chromosomes and one Y, and the rare red-eyed males had only one sex chromosome. The rare white-eyed females were XwXwY; they were white-eyed because they contained only recessive w alleles, and female because their X:A ratio = 2:2 = 1.0. The rare red-eyed males were X+O; they were red-eyed because of the dominant + allele, and male because their X:A ratio was 1:2 = 0.5. This demonstrated that genes that confer phenotypes were located on chromosomes.Explanation
Bridges used the Drosophila sex determination system and nondisjunction to demonstrate that the gene for red/white eye color is on the X chromosome. By examining the chromosomes of the rare flies, he observed that the white-eyed females had two X chromosomes and one Y, while the red-eyed males had only one sex chromosome. The white-eyed females were XwXwY, indicating that they contained only recessive w alleles and were female due to their X:A ratio of 2:2 = 1.0. On the other hand, the red-eyed males were X+O, indicating that they had the dominant + allele and were male due to their X:A ratio of 1:2 = 0.5. This provided evidence that genes responsible for phenotypes are located on chromosomes.Rate this question:
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May 29, 2012Quiz Created by
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