Unit 5: Sex Determination and Population Genetics - Practice Quiz

1 In mammals, which chromosome combination determines a male individual?

2 The gene primarily responsible for male development in mammals is located on which chromosome?

3 In Drosophila, sex is determined by the ratio of:

4 In Drosophila, an X:A ratio of produces which sex?

5 In Drosophila, an X:A ratio of produces which sex?

6 In birds, which sex is heterogametic?

7 The male sex chromosome constitution in birds is:

8 In many fishes, sex determination can be strongly influenced by which environmental factor?

9 Sex differentiation refers to:

10 In mammals, the undifferentiated gonad develops into a testis mainly under the influence of:

11 The Barr body observed in female mammalian cells represents:

12 How many Barr bodies are present in a normal human female (XX) somatic cell?

13 How many Barr bodies are found in a normal human male (XY) cell?

14 Dosage compensation in mammals ensures that:

15 In mammals, dosage compensation is achieved by:

16 The Hardy-Weinberg equilibrium is expressed by which equation?

17 Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

18 If the frequency of allele () is , what is the frequency of allele () in a two-allele system?

19 Genetic drift has the greatest effect in populations that are:

20 The movement of alleles between populations through the migration of individuals is called:

21 In birds, the female is the heterogametic sex. If a bird species follows the ZW system, what is the chromosomal constitution of a female?

22 Certain fish species can undergo natural sex reversal during their lifetime. This phenomenon best illustrates which type of sex determination?

23 A human individual has the karyotype (Klinefelter syndrome). Why does this individual develop as phenotypically male?

24 In Drosophila, an individual has 3 sets of autosomes (3A) and 2 X chromosomes. Using the genic balance theory, what is the expected phenotype?

25 A Drosophila with an X:A ratio of (i.e., 3X : 2A) would be classified as which of the following?

26 In mammalian sex differentiation, the Müllerian ducts regress in males primarily due to the action of which factor secreted by the developing testis?

27 In humans, the bipotential gonad develops into a testis rather than an ovary because of the expression of which gene during the critical window of development?

28 How many Barr bodies would be expected in the somatic cells of a human female with the karyotype ?

29 A Barr body represents which of the following in mammalian female cells?

30 Dosage compensation in Drosophila is achieved by which mechanism, in contrast to mammals?

31 In mammals, the initiation of X-chromosome inactivation is controlled by the expression of which non-coding RNA?

32 In a population at Hardy-Weinberg equilibrium, the frequency of the recessive homozygote () is . What is the frequency of the dominant allele ()?

33 Which of the following conditions must be satisfied for a population to remain at Hardy-Weinberg equilibrium?

34 For an autosomal gene at HWE with and , what is the expected frequency of heterozygotes in the population?

35 In a sample of 100 individuals, 36 are , 48 are , and 16 are . What is the allelic frequency of the allele?

36 A population has allele frequencies and . If the observed heterozygote frequency is , what does this indicate compared to HWE expectation?

37 The forward mutation rate () from allele to is much smaller than the effect of selection. What does this imply about mutation as an evolutionary force?

38 A large population receives migrants each generation such that migrants make up a fraction of the population. If the allele frequency in migrants is and in residents is , what is the new resident frequency after one round of migration?

39 A recessive lethal allele is subject to complete selection against homozygotes (). Why does this allele persist in the population for many generations?

40 Genetic drift has the strongest effect on allele frequencies under which of the following conditions?

41 In Drosophila, an individual has the chromosomal constitution with two sets of autosomes (). Based on the genic balance theory, what is the expected phenotypic sex?

42 A phenotypically female human is found to be with a mutation causing sex reversal. Which molecular defect most directly explains this Swyer syndrome phenotype?

43 In birds (ZW system), which observation provides the strongest evidence that a gene-dosage mechanism (via the Z-linked DMRT1) rather than a dominant W-linked factor drives male determination?

44 Many fishes exhibit temperature-dependent or environmental sex determination overriding genetic cues. Which scenario best illustrates that environmental sex determination can override an XY genotype in fish?

45 In a individual with complete androgen insensitivity syndrome (CAIS), why do external genitalia develop as female despite the presence of testes?

46 During mammalian sex differentiation, regression of the Müllerian ducts in males depends primarily on which secreted factor, and from which cells?

47 A buccal smear from a patient shows two Barr bodies per nucleus. Which karyotype is most consistent with this finding?

48 In neutrophils of a normal human female, the inactivated X often appears as a small drumstick-shaped appendage. Which statement about this structure and X-inactivation is correct?

49 Mammals and Drosophila both achieve dosage compensation but by opposite strategies. Which pairing correctly describes each mechanism?

50 The XIST long non-coding RNA is central to mammalian X-inactivation. Which statement most accurately describes its action?

51 For an X-linked recessive allele with frequency , what is the ratio of affected males to affected females in a large random-mating population at equilibrium?

52 In a population at Hardy-Weinberg equilibrium, the frequency of homozygous recessives is . If a random-mating error introduces complete positive assortative mating for this locus for one generation, what happens to the heterozygote frequency?

53 A codominant locus (M/N) shows MM, MN, and NN individuals in a sample of . Which conclusion about the allele frequencies and equilibrium is correct?

54 A recessive lethal allele causes death only in homozygotes before reproduction. Starting from , what is the allele frequency after one generation of selection ()?

55 A locus has forward mutation rate (A→a) and back mutation rate (a→A). What is the equilibrium frequency of allele under mutation pressure alone?

56 For a deleterious recessive allele maintained by mutation-selection balance with mutation rate and selection coefficient , what is the approximate equilibrium allele frequency?

57 An island population has allele frequency . Each generation, a fraction of the island consists of migrants from a mainland where . What is the island allele frequency after one generation of migration?

58 At a locus with heterozygote advantage, the fitnesses are , , . What is the stable equilibrium frequency of allele ?

59 Which statement best distinguishes the long-term effect of genetic drift in a small isolated population from that of directional selection?

60 A newly arisen neutral mutation appears as a single copy in a diploid population of effective size . What is its probability of eventual fixation by genetic drift?