Unit 3: Gene interaction and cytogenetics - Practice Quiz

1 What does cytology primarily study?

2 What is genetics the study of?

3 Cytogenetics is the study of the relationship between genetics and which cell component?

4 Which structure carries many genes in a cell?

5 How are cytology and genetics related?

6 Which field helps identify chromosome abnormalities associated with genetic disorders?

7 In a complete dominance relationship, what is the phenotype of a heterozygote?

8 What is the relationship in which both alleles are expressed in a heterozygote?

9 Which example demonstrates codominance?

10 What is incomplete dominance?

11 Red flowers crossed with white flowers produce pink flowers. This is an example of:

12 A recessive allele is expressed phenotypically in a diploid organism when it is usually present in:

13 What is epistasis?

14 In Labrador retrievers, the genotype prevents pigment deposition in the fur. This is an example of:

15 In dominant epistasis, the masking effect is produced by:

16 Which type of interaction involves two genes working together to produce a single phenotype?

17 Cytoplasmic inheritance is mainly controlled by genes located in the:

18 Which organelles commonly contain genetic material involved in cytoplasmic inheritance?

19 Why is mitochondrial inheritance often described as maternal inheritance?

20 Which statement best distinguishes cytoplasmic inheritance from nuclear inheritance?

21 In snapdragons, red flowers are crossed with white flowers, and all plants have pink flowers. If two pink plants are crossed, what phenotypic ratio is expected in the generation?

22 A person with blood group AB has a child with a person who has blood group O. Which blood groups are possible among their children?

23 A heterozygous genotype has a measurable enzyme activity of 80 units, while the two homozygotes have activities of 50 and 80 units. Which dominance relationship best describes enzyme activity?

24 In a plant species, genotypes , , and produce 20, 28, and 12 seeds per plant, respectively. Which relationship is shown by the heterozygote?

25 In Labrador retrievers, produces black pigment and produces brown pigment, but prevents pigment deposition and produces yellow fur. What phenotype is expected for a dog with genotype ?

26 Two dihybrid Labrador retrievers, , are crossed. If produces yellow fur, what fraction of the offspring is expected to be yellow?

27 Flower pigment is produced only when a plant has at least one dominant allele at both the and loci. What phenotypic ratio is expected from ?

28 In summer squash, produces white fruit regardless of the second locus, while produces yellow fruit and produces green fruit. Which ratio is expected from ?

29 Two independently assorting genes perform the same function, so a dominant allele at either locus produces the normal phenotype. Only is mutant. What ratio is expected from ?

30 A person has the genotype at the ABO locus but at the H locus and is phenotypically blood group O. What best explains this result?

31 A variegated female branch of Mirabilis jalapa is crossed with a green male branch, and the offspring include green, white, and variegated seedlings. Which observation best supports chloroplast inheritance?

32 A mitochondrial disorder is present in a woman and all her children, but an affected man does not transmit it to any of his children. Which inheritance pattern is most consistent with this pedigree?

33 Two siblings inherit the same pathogenic mitochondrial variant from their mother but show different disease severity. Which concept best explains this difference?

34 Reciprocal crosses for a trait produce different offspring phenotypes even though the nuclear genotypes of the offspring are equivalent. What is the most appropriate initial hypothesis?

35 A researcher wants to distinguish mitochondrial inheritance from an autosomal dominant pattern. Which result would provide the strongest evidence for mitochondrial inheritance?

36 A scientist uses microscopy to compare chromosome number and structure in normal and abnormal cells. Which field most directly covers this investigation?

37 Which pairing correctly matches each discipline with its primary focus?

38 A child has developmental abnormalities, and a pedigree alone does not reveal the cause. A karyotype shows three copies of chromosome 21. How does this illustrate the interrelation of the three fields?

39 A geneticist predicts that a mutation is caused by deletion of part of a chromosome. Which investigation most directly connects the genetic prediction with cellular evidence?

40 During meiosis, homologous chromosomes fail to separate, producing gametes with abnormal chromosome numbers. Which statement best integrates cytology and genetics?

41 At a pigment locus, genotypes , , and produce red, roan, and white coats, respectively. Microscopy shows that each hair in a roan animal is either entirely red or entirely white. Which interpretation best fits these observations?

42 Allele causes a short-tail phenotype in mice but is embryonic lethal in mice; mice have normal tails. Two short-tailed mice are crossed. Among 180 live offspring, what result is most consistent with the model?

43 A heterozygote has 60 enzyme units, whereas the two homozygotes have 100 and 0 units. Disease occurs below 40 units, so the heterozygote is clinically normal. Which conclusion is most accurate?

44 At one locus, adult viability relative to is 1.0 for , 1.4 for , and 0.7 for . Which dominance relationship applies specifically to adult viability?

45 Two pure lines with flower pigment scores 0 and 10 produce an score of 5. The contains scores 0, 5, and 10 in a ratio. Assuming one locus, which model is best supported?

46 In a dihybrid self, phenotype classes follow recessive epistasis: and are distinct, while and share a third phenotype. What is the probability that an individual with the third phenotype is ?

47 A cross yields three phenotypes in the ratio . Genotypes and have the same phenotype. Which interaction explains the ratio?

48 Flower pigment requires dominant alleles at both loci: only is purple, while every or plant is white. A purple dihybrid is selfed. Among white progeny, what fraction is expected to be ?

49 Either dominant allele at loci or produces capsules; only lacks capsules. In a self-cross of , capsule-bearing offspring are testcrossed to . Which parental genotype can produce only capsule-bearing testcross progeny?

50 In a dominant-suppression system, suppresses color regardless of , while is colored and is colorless. What phenotypic ratio is expected from ?

51 A woman has genotype at the ABO locus but at the H locus. A man is . Assuming classical Bombay epistasis, what blood-group phenotype does the woman express?

52 In Labrador retrievers, gives black pigment and gives brown pigment, but prevents pigment deposition and produces yellow. A black dog of genotype is crossed with a yellow dog of genotype . What ratio is expected?

53 Reciprocal crosses between a resistant female line and a sensitive male line produce resistant offspring, whereas the reverse cross produces sensitive offspring. Repeated backcrossing of daughters to males of the opposite phenotype preserves the maternal phenotype. Which hypothesis is strongest?

54 A heteroplasmic mother carries 30% mutant mitochondrial DNA in blood. Her children show mutant loads of 5%, 28%, and 82% and differ greatly in disease severity. Which mechanism best explains this dispersion?

55 A yeast petite mutant crossed with a wild-type strain yields almost exclusively petite descendants, but nuclear markers segregate normally. Which observation most strongly favors a cytoplasmic suppressive-petite mutation?

56 A snail's coiling direction is determined by the mother's nuclear genotype because gene products deposited in the egg establish early cleavage orientation. Why is this not cytoplasmic inheritance in the strict genetic sense?

57 A researcher correlates a visible reciprocal translocation with semisterility and maps its breakpoints using chromosome banding. Which discipline most directly integrates all parts of this investigation?

58 Which statement most precisely distinguishes cytology from genetics while preserving their overlap?

59 A phenotypically normal individual repeatedly produces conceptions with trisomy 21 caused by an inherited Robertsonian translocation. Which combined evidence best connects cytology, genetics, and cytogenetics?

60 A deletion is too small for routine karyotyping but is suspected from a Mendelian phenotype and developmental abnormalities. Which strategy best integrates the three fields?