Extensions – codominance, incomplete dominance, epistasis, pleiotropy, linkage, sex linkage - One Line Questions

1. In humans, the gene for Duchenne muscular dystrophy is X-linked recessive. If an unaffected father and a carrier mother have children, what is the probability of having an affected son? — 50%
2. In a cross between two snapdragons with genotype Rr (pink flowers), what proportion of the offspring will have red flowers? — 25%
3. If the recombination frequency between gene A and gene B is 20%, and between gene B and gene C is 30%, and they are in that order on a chromosome, what is the expected recombination frequency between gene A and gene C? — Could be 10% or 50% depending on interference
4. Consider a cross between two pea plants heterozygous for flower color, where red (R) is incompletely dominant over white (r). What would be the expected phenotypic ratio of the offspring? — 1 Red : 2 Pink : 1 White
5. A cross between a purebred white snapdragon and a purebred red snapdragon results in all pink offspring. If these pink offspring are self-crossed, what is the expected phenotypic ratio of their progeny? — 1 Red : 2 Pink : 1 White
6. In a particular breed of chickens, the allele for black feathers (B) is dominant over the allele for white feathers (b). However, a separate gene (E/e) controls feather color expression, where ee genotype results in white feathers regardless of the B/b alleles. If a cross is made between two BbEe chickens, what is the expected phenotypic ratio? — 3 Black : 1 White (due to epistasis)
7. In a dihybrid cross involving two linked genes with a recombination frequency of 50%, what phenotypic ratio would be expected in the offspring if the parents were heterozygous for both genes? — 9:3:3:1
8. If two genes are completely linked, what is the outcome of a dihybrid cross involving these genes? — The parental gamete types will be produced in a 1:1 ratio, with no recombinant types.
9. Incomplete dominance is often described as 'blending' inheritance. Which of the following best represents the genotype-phenotype relationship in incomplete dominance? — AA = Red, Aa = Pink, aa = White
10. In incomplete dominance, the heterozygous phenotype is typically a blend of the two homozygous phenotypes. What is an example of this in plants? — Snapdragon flower color
11. Which of the following is NOT a characteristic of X-linked recessive inheritance? — The trait appears more frequently in females than males.
12. Which type of inheritance pattern is observed in traits like Duchenne muscular dystrophy and red-green color blindness in humans? — X-linked recessive
13. Genes located on the sex chromosomes (X or Y) exhibit a pattern of inheritance known as: — Sex-linked inheritance
14. In a population, a specific gene is found on the X chromosome. Males inherit this gene only from their mother, and females inherit it from both parents. This describes: — Sex-linked inheritance
15. Hemophilia A, a bleeding disorder, is a classic example of a trait exhibiting: — X-linked recessive inheritance
16. In Labrador retrievers, the gene for pigment color (B/b) is epistatic to the gene for pigment deposition (E/e). If a dog has the genotype ee, what will its coat color be regardless of the B/b alleles? — Yellow
17. In mice, the gene for coat color has alleles B (black) and b (brown). Another gene determines whether pigment is deposited, with alleles E (deposition) and e (no deposition). If a mouse has genotype bbEE, what is its phenotype? — Brown
18. In chickens, the allele for dominant white plumage (W) masks the expression of the allele for black plumage (B), which is epistatic to the allele for white plumage (w). If a cross is made between a WWbb chicken and a wwBB chicken, what will be the phenotype of the F1 generation? — White
19. In the ABO blood group system, a person with blood type O has genotype ii. What is the phenotype of a person with genotype I^A i? — Blood type A
20. In humans, red-green color blindness is most commonly a result of a gene located on which chromosome? — X chromosome
21. A gene that affects the development of both the pigment in the fur and the size of the tail in mice is an example of: — Pleiotropy
22. Marfan syndrome, characterized by skeletal, ocular, and cardiovascular defects, is an example of which genetic phenomenon? — Pleiotropy
23. A single gene mutation causes a deficiency in a specific enzyme. This deficiency leads to the accumulation of a toxic substance, causing brain damage, and also affects the individual's height. This is a clear case of: — Pleiotropy
24. Phenylketonuria (PKU) is a metabolic disorder caused by a mutation in a single gene. However, the effects of PKU are widespread, including intellectual disability, eczema, and lighter skin pigmentation. This is an example of: — Pleiotropy
25. In the ABO blood group system, the allele for type O (i) is recessive to both the allele for type A (I^A) and the allele for type B (I^B). What is the relationship between I^A and I^B alleles? — Codominance
26. A plant breeder observes that crossing a red flower variety with a white flower variety produces only pink flowers. Self-pollinating the pink flowers results in 1/4 red, 1/2 pink, and 1/4 white offspring. This pattern is characteristic of: — Incomplete dominance
27. Which human genetic disorder is a classic example of pleiotropy, affecting multiple organ systems? — Sickle Cell Anemia
28. A single gene affecting multiple, seemingly unrelated phenotypic traits is known as: — Pleiotropy
29. A gene that influences the production of melanin, and also affects the development of the inner ear, leading to deafness in some individuals, exemplifies: — Pleiotropy
30. What is the term for the gene that is masked or hidden by the action of another gene? — Hypostatic gene
31. Which statement accurately describes sex-influenced inheritance? — Expression of a trait differs between sexes due to sex hormones, but the gene is autosomal.
32. When two genes are located far apart on the same chromosome, they tend to assort independently, behaving as if they were on different chromosomes. This is due to: — High frequency of crossing over
33. Epistasis describes a gene interaction where one gene masks or modifies the expression of another gene at a different locus. What is the gene that masks the expression called? — Epistatic gene
34. Which type of inheritance pattern occurs when both alleles for a trait are fully and simultaneously expressed in the heterozygous phenotype? — Codominance
35. In the ABO blood group system in humans, individuals with genotype AB express both A and B antigens. This is an example of: — Codominance
36. Linkage refers to the tendency of genes located close together on the same chromosome to be inherited together during meiosis. What phenomenon can overcome linkage? — Crossing over (recombination)
37. Which of the following is a characteristic of Y-linked inheritance? — It is passed from father to son.
38. Which of the following describes a situation where a single gene mutation leads to a cascade of effects, resulting in multiple phenotypic abnormalities? — Pleiotropy
39. Which of the following describes a situation where a gene on one chromosome influences the expression of a gene on another chromosome? — Epistasis
40. The genes for certain enzymes involved in the synthesis of a vitamin are located on different chromosomes. If a mutation in one of these genes prevents the synthesis of the vitamin, regardless of the alleles at the other locus, this is an example of: — Epistasis
41. If a trait is caused by a gene with multiple alleles, such as the ABO blood group system, what is the maximum number of alleles an individual can possess for that gene? — Two
42. If a gene controls the production of a pigment, and a mutation in this gene leads to albinism (lack of pigment), but also affects hearing and vision, this is an example of: — Pleiotropy
43. What is the term for the phenomenon where the allele at one gene locus masks or modifies the phenotypic expression of the alleles at another gene locus? — Epistasis
44. Which of the following is an example of epistasis where a dominant allele at one locus masks the expression of alleles at another locus? — Dominant epistasis (e.g., Squash fruit color)
45. Consider two genes, A and B, located on the same chromosome. If the recombination frequency between them is 10%, what does this indicate? — The genes are located 10 map units apart.
46. Two genes located on the same chromosome are said to be linked. If crossing over occurs between them, recombinant gametes are produced. The frequency of recombination is highest when: — The genes are far apart on the chromosome.
47. Baldness in human males is an example of sex-influenced inheritance. An allele for baldness may be dominant in males but recessive in females. This means the gene is located on: — An autosome
48. The phenomenon where genes on the same chromosome are inherited together is called linkage. The frequency of crossing over between two linked genes is proportional to: —
49. In Drosophila (fruit flies), the genes for eye color and wing shape are located on the same chromosome. If the recombination frequency between these genes is 5%, they are considered: — Tightly linked
50. Color blindness in humans is more prevalent in males than females. This is because the genes for color vision are primarily located on the: — X chromosome
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