Unit 2: Alleles, Gene Interactions and Cytoplasmic Inheritance - Practice Quiz

1 Which human blood group system is a classic example of multiple alleles?

2 Multiple alleles refer to the existence of:

3 In the four o'clock plant, a cross between red-flowered and white-flowered plants gives pink flowers. This is an example of:

4 In codominance, the heterozygote shows:

5 The AB blood group in humans, where both A and B antigens are present, is an example of:

6 An allelic series refers to:

7 The coat color of rabbits controlled by the alleles , , , and is a classic example of:

8 Epistasis is best defined as:

9 In recessive epistasis, the modified dihybrid ratio observed is:

10 The gene whose expression is masked by another gene is called the:

11 Pleiotropy refers to a condition where:

12 Which of the following is a well-known example of pleiotropy in humans?

13 Genomic imprinting is a phenomenon in which:

14 Genomic imprinting is primarily caused by which epigenetic mechanism?

15 Penetrance is defined as:

16 Expressivity refers to:

17 Cytoplasmic inheritance involves genes located in:

18 In humans, mitochondrial DNA is generally inherited from:

19 Chloroplast DNA is typically inherited in a pattern that is:

20 Streptomycin resistance in Chlamydomonas is an example of a trait inherited through:

21 In the human ABO blood group system, which of the following genotypes would produce an individual with blood group AB?

22 A cross between red-flowered () and white-flowered () snapdragons yields pink plants. If the plants are self-crossed, what phenotypic ratio is expected in the ?

23 Which of the following best distinguishes codominance from incomplete dominance?

24 In rabbit coat colour, the dominance order is . A rabbit with genotype would display which phenotype?

25 In a dihybrid cross, a modified ratio of 9 : 3 : 4 is observed. Which type of epistasis does this indicate?

26 A dihybrid cross gives an ratio of 12 : 3 : 1. This modified ratio is produced by which form of epistasis?

27 The 9 : 7 ratio observed in sweet pea flower colour is best explained by which type of gene interaction?

28 Which of the following is the best example of pleiotropy?

29 Which statement best describes genomic imprinting?

30 Prader-Willi and Angelman syndromes are classic examples of genomic imprinting because they:

31 If a dominant allele is present in 80 individuals but the associated phenotype is expressed in only 60, what is the penetrance?

32 Two individuals carry the same disease allele but one shows severe symptoms while the other shows only mild symptoms. This variation is described as:

33 Polydactyly shows incomplete penetrance. This means that some individuals who carry the dominant allele:

34 Which feature is most characteristic of cytoplasmic (extranuclear) inheritance?

35 A mother affected by a mitochondrial disorder (such as Leber's hereditary optic neuropathy) is expected to transmit the condition to:

36 Chloroplast DNA is generally inherited maternally in most angiosperms because:

37 Streptomycin resistance in Chlamydomonas is inherited in a non-Mendelian, uniparental manner. This is because the resistance gene is located in the:

38 In Mirabilis jalapa (four o'clock plant), the leaf variegation pattern of the offspring is determined by:

39 The killer trait in Paramecium requires kappa particles in the cytoplasm and a specific nuclear genotype. Which nuclear genotype is necessary to maintain kappa particles?

40 In the snail Limnaea, shell coiling direction is a maternal effect trait. The phenotype of an individual is determined by:

41 In the ABO blood group system, a couple where one parent is blood group AB and the other is blood group O are told by a genetics lab that their child is blood group O. Assuming no laboratory error or mutation, what is the most likely genetic explanation?

42 A single gene shows incomplete dominance for flower color (red RR, pink Rr, white rr) and simultaneously the same alleles are codominant for petal texture (R = smooth patch, r = rough patch, Rr = both patches). What phenotypic ratio for the combined traits is expected in the of an cross?

43 In rabbits, the coat color allelic series follows dominance . A full-color rabbit () is crossed with a Himalayan rabbit and produces offspring in a 1 full : 1 Himalayan ratio. Which genotypes of the parents are consistent with this result?

44 A dihybrid cross yields an ratio of 9 : 7. This modified ratio is diagnostic of which type of gene interaction?

45 In a certain plant, gene A is epistatic such that produces white flowers regardless of the B locus, while allows B-locus expression ( = purple, = red). What ratio results from a dihybrid cross?

46 Sickle-cell anemia is often cited as a classic example of pleiotropy. Which observation best demonstrates the pleiotropic nature of the allele?

47 Prader-Willi syndrome and Angelman syndrome can both result from deletions in the same 15q11-q13 chromosomal region, yet produce very different phenotypes. What best explains this?

48 A dominant allele causes a disorder with 70% penetrance. If a heterozygous () affected individual mates with an unaffected homozygous recessive () partner, what fraction of the offspring are expected to actually show the disorder?

49 Two patients carry the identical mutant allele for neurofibromatosis, yet one shows only a few café-au-lait spots while the other has extensive tumors and skeletal deformities. This variation in the degree of phenotypic expression among individuals with the same genotype is best described as:

50 Which of the following features would MOST strongly distinguish a case of cytoplasmic (extranuclear) inheritance from an autosomal recessive nuclear trait?

51 A woman with a mitochondrial disorder (heteroplasmic mtDNA mutation) has several children. Which pattern is expected, and why can severity differ among her children?

52 In most angiosperms, chloroplast DNA is maternally inherited. However, in some gymnosperms and a few angiosperms, chloroplasts can be paternally or biparentally transmitted. This variation is best attributed to:

53 In Chlamydomonas, streptomycin resistance () is inherited through the chloroplast. In a cross between () and (), what is the expected outcome in the offspring, given that the parent transmits its chloroplast?

54 In Mirabilis jalapa (four o'clock plant), variegated branches bear green, white, and variegated regions. If flowers on a variegated branch are pollinated by pollen from a green branch, what phenotypes appear in the progeny?

55 In Paramecium, killer strains carry cytoplasmic kappa particles and require the nuclear dominant gene to maintain them. During conjugation without cytoplasmic exchange, a killer (, with kappa) conjugates with a sensitive (, no kappa). What are the exconjugant phenotypes?

56 In Limnaea, shell coiling is controlled by a maternal-effect gene where dextral (D) is dominant to sinistral (d). A genotypically snail displays dextral coiling. What must have been the genotype of this snail's mother?

57 A dihybrid self-cross produces an ratio of 9 : 3 : 4. Which mechanism explains the 4-class?

58 Suppose a gene has different alleles in a population. How many distinct genotypes (including both homozygous and heterozygous combinations) are theoretically possible at this locus?

59 Which molecular mechanism is primarily responsible for establishing genomic imprinting, allowing a gene to be silenced according to its parent of origin during gametogenesis?

60 The 'threshold effect' in mitochondrial diseases explains why symptoms appear only when the proportion of mutant mtDNA exceeds a critical level. Why do tissues like brain and muscle typically manifest symptoms at lower mutant loads than others?