Q&A Hero

Q: Nondisjunction of the X chromosomes may occur during formation of gametes and produce two kinds of eggs. If normal sperm fertilizes these two kinds of eggs, which of the following pairs of genotypes are possible? A) XX and XY B) XXY and XO C) XYY and XO D) XYY and YO

Q: If a zygote has the genotype XYY, how many total chromosomes were in the sperm before it fused with the egg? A) 20 B) 21 C) 22 D) 23 E) 24

Q: A person with the genotype XO is mainly female, phenotypically. A person with the genotype XXY is mainly male. What can you conclude about the Y chromosome? A) It has the same genes as X, just different alleles. B) It has the same genes as X, in different orientation. C) A Y chromosome confers maleness, regardless of the number of X chromosomes. D) The only genes it carries are for female development. E) A human cannot survive without a Y chromosome.

Q: A woman is missing one of her X chromosomes. With which of the following conditions would she be diagnosed? A) Turner syndrome B) polyploidy C) a chromosomal deletion D) Klinefelter syndrome E) cancer

Q: If a diploid cell from an organism has 46 chromosomes, how many chromosomes are likely to be found in a gamete that is the result of nondisjunction? A) 46 or 92 B) 23 or 22 C) 21 or 22 D) 22 or 24 E) 24 or 25

Q: Aneuploid human embryos are least likely to survive except those involving: A) chromosome 1, 2, 3, X, Y. B) chromosome 1, 2, 3, 4, 5. C) chromosome 13, 18, 21, X, Y. D) chromosome 6, 7, 8, 9, 10. E) chromosome 11, 12, 14, 15.

Q: Down syndrome in humans is caused by: A) an extra X chromosome. B) an extra y chromosome. C) three copies of chromosome 21. D) three copies of chromosome 13. E) a single copy of chromosome 21.

Q: In humans, aneuploidy is fairly common yet goes largely unrecognized as a genetic problem. This is because: A) it produces autosomal recessive individuals who don't always express the disorder. B) its effects are usually hidden. C) it actually produces healthy individuals. D) it often results in miscarriage of embryos.

Q: What is nondisjunction? A) failure of sperm and egg to fuse in fertilization B) failure of cells to divide by cytokinesis in meiosis C) failure of chromosomes to duplicate before mitosis or meiosis D) failure of homologous chromosomes or sister chromatids to separate in meiosis E) an extra duplication of the chromosomes before mitosis or meiosis

Q: What is one difference between polyploidy and aneuploidy? A) Polyploidy is extra sets of chromosomes; aneuploidy occurs when there are either more or fewer chromosomes than normally exist in its species full set. B) Humans can be viable as polyploids but not as aneuploids. C) Polyploidy is extra sex chromosomes; aneuploidy is extra autosomes. D) Polyploidy is one extra chromosome; aneuploidy is one missing chromosome. E) Polyploidy causes diseases and disorders in humans; aneuploidy does not.

Q: The state of having more than two sets of chromosomes is called: A) autosomal. B) dominant. C) polyploidy. D) aneuploidy. E) nondisjunction.

Q: The human genome has how many pairs of autosomal chromosomes? A) 46 pairs B) 44 pairs C) 23 pairs D) 22 pairs E) 24 pairs

Q: If more than one sperm fertilizes an egg, which of the following can result? A) an autosomal dominant disorder B) an autosomal recessive disorder C) aneuploidy D) polyploidy

Q: You are tracking the inheritance of a genetic disorder through a family's pedigree, and you notice that it shows up in every generation. The disorder is most likely: A) recessive. B) dominant. C) X-linked recessive.

Q: A pedigree is a representation of: A) a genetic family tree. B) a series of chromosomes arranged in order. C) the inheritance pattern of recessive disorders. D) the inheritance pattern of dominant disorders. E) all the genetic disorders that can be inherited.

Q: A study of several pedigrees demonstrates that two parents are normal. If some of their children express a trait, then the trait is controlled by a: A) codominant gene. B) simple dominant gene. C) recessive gene. D) sex-linked gene.

Q: In a pedigree chart, a darkened square demonstrates a: A) diseased male. B) diseased female. C) normal male. D) normal female.

Q: Which of the following genetic disorders is caused by a dominant allele but does not produce symptoms until the affected individual is well into adulthood? A) Turner syndrome B) Down syndrome C) Huntington disease D) sickle-cell anemia E) hemophilia

Q: Which of the following is an autosomal recessive disorder? A) hemophilia B) Huntington disease C) Down syndrome D) sickle-cell anemia E) Turner syndrome

Q: What is the connection between sickle-cell anemia and malaria? A) Both are X-linked. B) Both are autosomal recessive. C) Both are dominant. D) Heterozygotes for malaria have some resistance to sickle-cell anemia. E) Heterozygotes for sickle-cell anemia have some resistance to malaria.

Q: A person who has a recessive disorder but does not have the disorder him or herself is said to be a/an: A) aneuploid. B) aberration. C) carrier. D) hybrid.

Q: What condition is caused by a dominant allele of a single gene? A) Down syndrome B) sickle-cell anemia C) Huntington disease D) color blindness E) Turner syndrome

Q: A person with an inherited disorder has children with a person who does not have the condition. Half the children have the disorder, both sons and daughters. How is this condition inherited? A) autosomal dominant B) autosomal recessive C) X-linked dominant D) X-linked recessive E) aneuploidy

Q: A person who is heterozygous for the Huntington disease (HD) allele has offspring with someone who does not have HD. What proportion of their children will have HD? A) 1/16 B) 1/10 C) 1/8 D) 1/4 E) 1/2

Q: If a disease is caused by a dominant allele, it means that a person with the disease: A) will always pass it on to all their children. B) will pass it on to one-fourth of their children. C) must be homozygous dominant for the allele. D) must be heterozygous for the allele. E) could be either homozygous or heterozygous for the allele.

Q: Genes not found on the sex chromosomes will be found on: A) X chromosomes. B) Y chromosomes. C) autosomes. D) centrosomes.

Q: An autosomal recessive disorder: A) requires that only one parent be a carrier. B) displays its symptoms only in heterozygotes. C) is more frequent in males than females. D) will appear only in children of parents who both carry the gene. E) is dominant in females.

Q: Who is a "carrier" of X-linked disorders, such as hemophilia and color blindness? A) a person who has the X-linked disorder B) a heterozygous female who is normal but carries one nonfunctioning allele C) a homozygous female who carries the normal alleles D) a male who carries the nonfunctioning allele E) a male who carries the functioning allele

Q: Color blindness is caused by an X-linked recessive gene. A color-blind man and a woman with normal vision whose father was color blind have a son. The probability that their son is color blind is: A) 0.25 (or 25 percent). B) 0.50 (or 50 percent). C) 0.75 (or 75 percent). D) 1.00 (or 100 percent). E) none of these.

Q: Red-green color blindness is an X-linked recessive trait in humans. A color-blind woman and a man with normal vision have a son. What is the probability that the son is color blind? A) 100 percent B) 75 percent C) 50 percent D) 25 percent E) 0 percent

Q: If a daughter expresses an X-linked recessive gene, she probably inherited the trait from: A) her mother. B) her father. C) both parents. D) neither parent. E) her grandmother.

Q: What do hemophilia, Duchenne muscular dystrophy, and red-green color blindness have in common? A) They are X-linked. B) They are more common in females than in males. C) They are caused by inheritance of an extra sex chromosome. D) They are caused by inheritance of an extra autosome. E) The gene that causes them is on the Y chromosome.

Q: Why do X-linked conditions appear more frequently in males than in females? A) A male with a nonfunctioning allele on the X chromosome does not have another allele of that gene on the Y chromosome that could cover up the nonfunctioning one. B) Males have no X chromosomes. C) The Y chromosome carries many alleles that are recessive to alleles on the X chromosome. D) Males are more likely to inherit an extra chromosome than females. E) Females have no X chromosomes.

Q: What is a recessive disorder? A) a genetic disorder with two functioning alleles B) a genetic disorder that will express itself in the presence of one functioning allele C) a genetic disorder that will express itself in the presence of two recessive alleles D) a genetic disorder that involves change in chromosome number E) a genetic disorder that involves change in chromosome structure

Q: A trait such as albinism is seen with equal frequency in males and females. Two people who do not have the trait might have offspring who do have the trait, at a frequency of approximately one in four. What can you conclude about the inheritance of this trait? A) recessive, X-linked B) recessive, autosomal C) recessive, caused by polyploidy D) dominant, X-linked E) dominant, autosomal

Q: What percent of males have some degree of color blindness? A) 0.5 percent B) 5 percent C) 0.8 percent D) 8 percent E) 10 percent

Q: Regarding the human sex chromosomes, which statement is correct? A) The Y chromosome carries a greater number of genes than does the X chromosome. B) X and Y are different in size but carry nearly equal numbers of genes. C) The X chromosome carries more genes than does the Y chromosome. D) The X chromosome carries only gender-related genes. E) The X chromosome carries the genes for the development of male phenotype.

Q: A woman who does not carry the color-blindness allele has children with a man who is color blind. What proportion of their children will be color blind? A) all B) 1/4 C) 1/2 D) 3/4 E) none

Q: A woman who is a carrier for the hemophilia gene has a child with a man who does not have hemophilia. Which prediction is correct? A) All of the sons and none of the daughters will have hemophilia. B) All of the daughters and none of the sons will have hemophilia. C) Half of the sons and half of the daughters will have hemophilia. D) Half of the sons and none of the daughters will have hemophilia. E) Half of the daughters and none of the sons will have hemophilia.

Q: Refer to the figure below, and then answer the question that follows.In a dihybrid cross, if heterozygotes are crossed, what fraction of the offspring is expected to have both the dominant phenotypes?A) 1/16B) 1/3C) 2/3D) 3/16E) 9/16

Q: Refer to the figure below, and then answer the question that follows. In his basic experiments, Mendel began with true-breeding parental (P) plants. What results did he see when he cross-fertilized P generation plants that had different traits?A) The F1plants had new traits that were a blend of P traits.B) All F1plants had the trait of one or the other P plant.C) The F1plants had an entirely new trait, not seen in either P plant.D) The F1plants showed a combination of the two P traits in a 1:1 ratio.E) The F1plants showed a combination of the two P traits, in a 3:1 ratio.

Q: Identical twins are genetically the same but do not always look or act exactly alike. Propose a hypothesis to explain this.

Q: Hydrangeas can have either pink or blue flowers. You want to test if the flower color is influenced by the environment, such as the acidity of the soil. Design an experiment to test if soil acidity affects flower color.

Q: A man with type O blood has a sister with type AB blood. What are the genotypes and phenotypes of their parents?

Q: The inheritance of curly hair illustrates incomplete dominance. When a curly haired individual reproduces with a straight-haired one, the children all have wavy hair. What offspring would be produced, in what proportions, when two people with wavy hair reproduce?

Q: Consider the following information for a dihybrid cross. The dominant allele F codes for freckles, whereas the recessive allele f codes for no freckles. The dominant allele E codes for long eyelashes, whereas the recessive allele e codes for short eyelashes. Both parents have the genotypes of ee and Ff. Indicate the following: (1) the phenotype of both parents, (2) the possible gametes that each parent can make, (3) all of the possible phenotypes for the offspring, and (4) the phenotypic ratio obtained after the Punnett square is drawn.

Q: When Mendel performed a dihybrid cross of plants heterozygous for seed color and seed shape, he saw a 9:3:3:1 ratio in the next generation. Explain what this ratio describes and what each number represents.

Q: What is the difference between a monohybrid and a dihybrid cross?

Q: If an individual has genotype AaBb, how many different gametes can he or she produce? What combinations of alleles are possible?

Q: Cystic fibrosis (CF) is a disease caused by a recessive allele, and the disease appears only in the homozygous recessive genotype. Two parents do not have cystic fibrosis, but they produce a child with this disorder. Fully explain what has occurred, using the appropriate terminology and diagram (you must provide this diagram).

Q: In a breeding experiment with yellow and green true-breeding parents, Mendel took yellow seeds from his F2generation, planted them, and self-pollinated the flowers to produce an F3generation. He saw that some produced all yellow seeds, and some produced a mix of yellow and green seeds. How can these results be explained?

Q: List two characteristics of the garden pea plant, Pisum sativum, that make it an ideal organism for genetic experiments.

Q: A true-breeding strain of red tulips is crossed to a true-breeding strain of white tulips. All the offspring have pink flowers. When a pink-flowered plant is self-fertilized, the offspring have red, pink, and white flowers, in the ratio 1:2:1. This type of inheritance is an example of ________.

Q: If a plant heterozygous for the genes for both seed color and shape is self-fertilized, the ratio of offspring with smooth, green seeds is ________/16. (Yellow and smooth are the dominant phenotypes.)

Q: In the Law of ________, Mendel stated that two genetic elements are separated in gamete formation.

Q: A particular quality of an organism is referred to as a ________, each variation of which is a particular ________.

Q: The physical characteristics of an organism, or its ________, are determined by its genetic makeup, referred to as its ________.

Q: Match the following.A) Alleles come in dominant and recessive forms.B) There is no "blending" in inheritance.C) Neither allele is completely dominant over the other.D) Genes assort independently in gamete formation.The crossing of two true-breeding parents seems to produce a blending in the F1generation, but the dominant and recessive traits are expressed again in the F2 generation.

Q: Match the following.A) Alleles come in dominant and recessive forms.B) There is no "blending" in inheritance.C) Neither allele is completely dominant over the other.D) Genes assort independently in gamete formation.When two traits are followed in a dihybrid cross, heterozygotes in the F1generation produce offspring with all combinations of phenotypes, in a 9:3:3:1 ratio.

Q: Match the following.A) Alleles come in dominant and recessive forms.B) There is no "blending" in inheritance.C) Neither allele is completely dominant over the other.D) Genes assort independently in gamete formation.When true-breeding P plants are crossed, all offspring have the trait of one of the parents.

Q: Match the following.A) Alleles come in dominant and recessive forms.B) There is no "blending" in inheritance.C) Neither allele is completely dominant over the other.D) Genes assort independently in gamete formation.When true-breeding P plants of different types are crossed, the offspring do not have a phenotype intermediate between the two parents.

Q: When two individuals with different traits are crossed, either the dominant or the recessive trait, and not an intermediate trait, is always seen, no matter what the organism or phenotype.

Q: If a person has a recessive trait, the genotype must be homozygous recessive for the trait.

Q: Mendel's crosses with pea plants disproved the notion that, when individuals with two different traits are mated, the genetic information blends in the offspring and is not retained as separate elements.

Q: Mendel's contribution to genetics was the discovery of DNA.

Q: The phenotype of an organism can be influenced by: A) its genotype. B) its environment. C) both its environment and its genotype. D) neither its genotype nor its environment.

Q: Characters such as height, weight, and skin color are controlled by many genes acting together. These are examples of: A) multiple alleles. B) codominance. C) incomplete dominance. D) polygenic inheritance.

Q: Height is an example a character that displays continuous variation in humans. What is the reason for the range of heights in humans? A) There is incomplete dominance of the tall allele over the short allele. B) There are multiple alleles for the height gene. C) Most traits such as height are governed by the interaction of many genes. D) There is only one gene for height in humans, but the environment can influence the expression of the gene.

Q: A, B, and O blood type in humans is controlled by a single gene with three alleles: IA, IB, and i. Type O is the recessive trait. The i allele is recessive to both IAand IB. Which of the following could be possible genotypes of the parents of a person with type O blood? A) IAIB and ii B) IAiand IAIA C) IAiand IBi D) IAIBand IAIB

Q: What is the significance of multiple alleles? A) They make it possible for one person to have more than two alleles for a gene. B) They are the reason one gene can affect more than one character. C) They are the reason the environment can affect characters. D) They allow for a range of traits in the population.

Q: Which type of inheritance is most likely to display a bell curve of phenotypes? A) codominance B) multiple alleles C) polygenic inheritance D) monohybrid cross E) incomplete dominance

Q: What is the basis of codominance? A) There is only one allele for a gene. B) One allele of a gene encodes a protein, and the other allele is nonfunctional. C) One gene has many alleles. D) Each allele of a gene produces a protein that functions to create a trait. E) One allele can have many effects on a phenotype.

Q: A person with the genotype IAIBhas type AB blood. This is an example of: A) the effect of the environment on phenotype. B) dihybridness. C) monohybridness. D) codominance. E) incomplete dominance.

Q: Crossing a true-breeding red-flowered snapdragon with a true-breeding white-flowered snapdragon produces all pink snapdragons in the F1generation. If F1individuals are crossed, what will be the ratio of phenotypes in the F2generation? A) 1 red:1 pink: 2 white B) 2 red:1 pink: 2 white C) 1 red: 2 pink: 1 white D) 3 pink: 1 white E) 3 white: 1 pink

Q: If all of Mendel's monohybrid crosses had involved traits that function by incomplete dominance, would his results have supported blending inheritance? A) It cannot be determined with the information given. B) Yes; a cross between red and white flowers would yield all pink offspring. C) No; he would still have seen the dominant and recessive traits reappear in the F2 generation. D) Yes; there is always a wide range of phenotypes in monohybrid crosses.

Q: A plant that produces white flowers is crossed to a plant that produces orange flowers. All the offspring produced pale orange flowers. What can you conclude? A) Pale orange flower is the dominant phenotype. B) This trait shows incomplete dominance. C) Orange flower is the dominant phenotype. D) The genes for flower color do not assort independently. E) White flower is the dominant phenotype.

Q: What is the basis for incomplete dominance? A) Both alleles of a gene produce weakly functioning proteins. B) One allele produces some functioning protein; the other allele is nonfunctional. C) Crossing over has switched alleles for a gene on homologous chromosomes. D) One gene has many effects. E) An individual has more than two alleles for a gene.

Q: Crossing two pink snapdragons yields some seeds that produce red-flowering plants, some seeds that produce white-flowering plants and some seeds that produce pink-flowering plants. If this trait operates by incomplete dominance and the allele R represents red flowers and the allele r represents white flowers, what genotype would a plant with pink flowers have for this trait? A) RR B) Rr C) rr D) RrRr

Q: Mendel's work was presented in ________ but not recognized and rediscovered until ________. A) 1825; 1950 B) 1865; 1900 C) 1850; 1900 D) 1800; 1900 E) 1890; 1920

Q: In Mendel's pea plants, yellow seeds are dominant to green seeds. Purple flowers are dominant to white flowers. Use Y and y for the seed color alleles and P and p for the flower color alleles. Flower color and seed color assort independently. What is the relationship between the Y and P? A) They are two different genes on two different chromosomes. B) They are two different genes on the same chromosome. C) They are two different chromosomes in the pea plant. D) They are the pleiotropic effects of a single gene. E) They are incompletely dominant alleles of the same gene.