TRB PG Assistant - Extensions – codominance, incomplete dominance, epistasis, pleiotropy, linkage, sex linkage Online Test (MCQ Quiz)

1. Which type of inheritance pattern occurs when both alleles for a trait are fully and simultaneously expressed in the heterozygous phenotype?

A) Incomplete Dominance B) Codominance C) Epistasis D) Pleiotropy

2. In incomplete dominance, the heterozygous phenotype is typically a blend of the two homozygous phenotypes. What is an example of this in plants?

A) ABO blood groups in humans B) Snapdragon flower color C) Feather color in chickens D) Coat color in Labrador retrievers

3. 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?

A) Hypostatic gene B) Epistatic gene C) Dominant gene D) Recessive gene

4. A single gene affecting multiple, seemingly unrelated phenotypic traits is known as:

A) Epistasis B) Linkage C) Pleiotropy D) Sex linkage

5. Which human genetic disorder is a classic example of pleiotropy, affecting multiple organ systems?

A) Cystic Fibrosis B) Sickle Cell Anemia C) Huntington's Disease D) Down Syndrome

6. 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?

A) Independent assortment B) Crossing over (recombination) C) Epistasis D) Complete dominance

7. Genes located on the sex chromosomes (X or Y) exhibit a pattern of inheritance known as:

A) Autosomal inheritance B) Sex-linked inheritance C) Mitochondrial inheritance D) Mendelian inheritance

8. In humans, red-green color blindness is most commonly a result of a gene located on which chromosome?

A) Chromosome 1 B) Autosome 15 C) X chromosome D) Y chromosome

9. 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?

A) 3 Red : 1 White B) 1 Red : 2 Pink : 1 White C) 2 Red : 1 White D) 1 Red : 1 White

10. 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?

A) Black B) Chocolate C) Yellow D) Brown

11. 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:

A) Codominance B) Incomplete dominance C) Pleiotropy D) Epistasis

12. If two genes are completely linked, what is the outcome of a dihybrid cross involving these genes?

A) A 9:3:3:1 phenotypic ratio B) A 1:1:1:1 phenotypic ratio C) A 3:1 phenotypic ratio D) The parental gamete types will be produced in a 1:1 ratio, with no recombinant types.

13. Hemophilia A, a bleeding disorder, is a classic example of a trait exhibiting:

A) Autosomal recessive inheritance B) X-linked recessive inheritance C) Autosomal dominant inheritance D) Y-linked inheritance

14. What is the term for the gene that is masked or hidden by the action of another gene?

A) Epistatic gene B) Hypostatic gene C) Suppressor gene D) Modifier gene

15. In the ABO blood group system in humans, individuals with genotype AB express both A and B antigens. This is an example of:

A) Incomplete dominance B) Codominance C) Epistasis D) Pleiotropy

16. Which of the following describes a situation where a single gene mutation leads to a cascade of effects, resulting in multiple phenotypic abnormalities?

A) Linkage B) Sex linkage C) Pleiotropy D) Epistasis

17. 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:

A) Their location on different chromosomes B) The distance between them C) The total number of genes on the chromosome D) The presence of dominant alleles

18. Color blindness in humans is more prevalent in males than females. This is because the genes for color vision are primarily located on the:

A) Y chromosome B) Autosomes C) X chromosome D) Mitochondrial DNA

19. 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?

A) 3 Red : 1 White B) 1 Red : 2 Pink : 1 White C) 2 Red : 1 Pink D) 1 Red : 1 Pink

20. 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?

A) 9 Black : 3 White : 3 Black : 1 White (9:3:3:1) B) 3 Black : 1 White C) 1 Black : 2 White : 1 Black (1:2:1) D) 3 Black : 1 White (due to epistasis)

21. Marfan syndrome, characterized by skeletal, ocular, and cardiovascular defects, is an example of which genetic phenomenon?

A) Codominance B) Epistasis C) Pleiotropy D) Linkage

22. 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:

A) High frequency of crossing over B) Complete linkage C) Epistatic interaction D) Recessive epistasis

23. Which of the following is NOT a characteristic of X-linked recessive inheritance?

A) Affected males typically have unaffected mothers. B) Affected females must have at least one affected father. C) The trait appears more frequently in females than males. D) Affected males pass the allele to all their daughters, who are usually carriers.

24. 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?

A) Complete dominance B) Incomplete dominance C) Codominance D) Epistasis

25. 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:

A) Pleiotropy B) Epistasis C) Linkage D) Sex linkage

26. Consider two genes, A and B, located on the same chromosome. If the recombination frequency between them is 10%, what does this indicate?

A) The genes are completely linked. B) The genes are located 10 map units apart. C) The genes assort independently. D) The genes exhibit epistasis.

27. Which of the following describes a situation where a gene on one chromosome influences the expression of a gene on another chromosome?

A) Linkage B) Sex linkage C) Epistasis D) Pleiotropy

28. 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?

A) 0% B) 25% C) 50% D) 100%

29. 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:

A) Complete dominance B) Codominance C) Incomplete dominance D) Epistasis

30. 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?

A) Black B) Brown C) Albino D) Gray

31. Which of the following is an example of epistasis where a dominant allele at one locus masks the expression of alleles at another locus?

A) Recessive epistasis (e.g., Labrador coat color) B) Dominant epistasis (e.g., Squash fruit color) C) Incomplete dominance (e.g., Snapdragon color) D) Codominance (e.g., ABO blood groups)

32. 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:

A) Linkage B) Pleiotropy C) Epistasis D) Codominance

33. 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:

A) Autosomal inheritance B) Sex-linked inheritance C) Mitochondrial inheritance D) Maternal effect

34. 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?

A) One B) Two C) Three D) Four

35. 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:

A) Codominance B) Epistasis C) Pleiotropy D) Linkage

36. 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:

A) Unlinked B) Completely linked C) Loosely linked D) Tightly linked

37. Which of the following is a characteristic of Y-linked inheritance?

A) It affects both males and females equally. B) It is passed from father to son. C) It is passed from mother to offspring. D) It involves genes on the X chromosome.

38. In a cross between two snapdragons with genotype Rr (pink flowers), what proportion of the offspring will have red flowers?

A) 0% B) 25% C) 50% D) 75%

39. 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?

A) Black B) White C) Gray D) Black and white mottled

40. A gene that influences the production of melanin, and also affects the development of the inner ear, leading to deafness in some individuals, exemplifies:

A) Epistasis B) Codominance C) Pleiotropy D) Linkage

41. 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:

A) The genes are very close together. B) The genes are far apart on the chromosome. C) One gene is dominant and the other is recessive. D) The genes are on different chromosomes.

42. Which type of inheritance pattern is observed in traits like Duchenne muscular dystrophy and red-green color blindness in humans?

A) Autosomal dominant B) Autosomal recessive C) X-linked recessive D) Y-linked

43. 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?

A) Blood type A B) Blood type B C) Blood type AB D) Blood type O

44. 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:

A) Codominance B) Epistasis C) Pleiotropy D) Linkage

45. 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?

A) 10% B) 50% C) Could be 10% or 50% depending on interference D) Cannot be determined without knowing if they are linked or unlinked

46. 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?

A) Pleiotropy B) Codominance C) Incomplete dominance D) Epistasis

47. 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?

A) 9:3:3:1 B) 3:1 C) 1:1:1:1 D) 1:2:1

48. Which statement accurately describes sex-influenced inheritance?

A) Genes located on sex chromosomes. B) Expression of a trait differs between sexes due to sex hormones, but the gene is autosomal. C) Complete dominance where one allele is always dominant. D) Masking of one gene by another.

49. 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:

A) The X chromosome B) The Y chromosome C) An autosome D) Mitochondrial DNA

50. Incomplete dominance is often described as 'blending' inheritance. Which of the following best represents the genotype-phenotype relationship in incomplete dominance?

A) AA = Red, Aa = Pink, aa = White B) AA = Red, Aa = Red, aa = White C) AA = Red, Aa = AB, aa = White D) AA = Red, Aa = Red & White, aa = White

Extensions – codominance, incomplete dominance, epistasis, pleiotropy, linkage, sex linkage - Online Test

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