Unit 4: Patterns of inheritance, sex-linked genetics and genetic mutations - Practice Quiz

1 What is meant by multiple alleles?

2 How many alleles of a particular autosomal gene can a diploid individual normally carry?

3 What is pleiotropism?

4 What are pseudoalleles?

5 What type of relationship exists between the and alleles in the ABO blood group system?

6 Which genotype produces blood group O?

7 Which pair of genotypes can produce blood group A?

8 Which chromosome combination normally determines a human male?

9 Why are X-linked recessive traits more commonly expressed in human males?

10 Which parent determines the chromosomal sex of a human child?

11 Which is a common example of a sex-limited trait?

12 Which human characteristic is commonly used as an example of a sex-influenced trait?

13 Two independent genetic events each have a probability of . What is the probability that both events occur?

14 What is the main purpose of a chi-square test in genetics?

15 What is a mutation?

16 A change affecting a single nucleotide pair is generally called a:

17 Which type of mutation can result from inserting or deleting nucleotides not in multiples of three within a coding sequence?

18 Which is a standard method used to induce mutations experimentally?

19 Which physical agent can act as a mutagen?

20 What is an induced mutation?

21 In rabbits, the coat-color alleles follow the dominance order . A cross is made between and . What phenotypic ratio is expected among the offspring?

22 A gene has five alleles in a population. How many different alleles of this gene can a normal diploid individual carry at the same time?

23 A single mutation causes abnormal hemoglobin, anemia, pain during low-oxygen conditions, and resistance to severe malaria. Which genetic phenomenon best explains these effects?

24 Two recessive mutations produce nearly identical eye defects and map extremely close together. Rare wild-type offspring appear when individuals carrying the mutations on different homologues are crossed. What is the best interpretation?

25 A person with genotype has children with a person of genotype . What is the probability that a child will have blood group O?

26 A woman has genotype and therefore has the Bombay phenotype. She has children with a man of genotype . Assuming independent assortment, what fraction of their children is expected to show blood group B?

27 A woman heterozygous for an X-linked recessive disorder has children with an unaffected man. If they have two sons, what is the probability that exactly one son will be affected?

28 In a bird species, females are and males are . A dominant Z-linked allele produces barred feathers. A barred female is crossed with an unbarred male . Which result is expected?

29 Two X-linked genes are 20 map units apart. A female has genotype and is crossed with an male. What proportion of their sons is expected to inherit the maternal chromosome?

30 An allele for pattern baldness is dominant in males but recessive in females. Two heterozygous individuals, , have a son and a daughter. What are their respective probabilities of being bald?

31 A bull carries an allele associated with high milk production but does not produce milk. Several of his daughters show high milk production. How should this trait be classified?

32 In the self-cross , the two genes assort independently. What is the probability that an offspring shows a recessive phenotype for exactly one of the two traits?

33 A dihybrid cross produces four phenotypic classes with observed counts 315, 108, 101, and 32. Under a expectation, the expected counts are 312.75, 104.25, 104.25, and 34.75. What is the approximate value of ?

34 Parallel bacterial cultures started from small inocula produce highly variable numbers of antibiotic-resistant colonies before exposure to the antibiotic. What does this observation support?

35 A DNA base pair changes from to . How is this base substitution classified?

36 One nucleotide is inserted near the beginning of a protein-coding sequence. No compensating insertion or deletion occurs. What is the most likely consequence?

37 A point mutation changes the mRNA codon , which encodes tyrosine, into . What type of mutation has occurred?

38 A researcher wants to determine an effective ultraviolet dose for inducing mutations in fungal spores. Which experimental design is most appropriate?

39 A chemical inserts between stacked DNA base pairs and frequently causes single-base insertions or deletions during replication. Which type of mutagen is it?

40 Seeds are treated with EMS to induce recessive mutations. Why are plants with new recessive phenotypes commonly screened in the generation rather than only in the generation?

41 At a locus with four alleles, , , , and , every pair of alleles produces a distinct phenotype, including homozygotes. How many phenotypically distinct genotypes are possible in a diploid population?

42 In a multiple-allele system, allele is dominant to , while both are dominant to . A phenotypically dominant individual is crossed with an individual of genotype , producing offspring in the ratio dominant phenotype to intermediate phenotype to recessive phenotype. Which genotype best describes the first parent?

43 A mutation in gene causes reduced pigment, abnormal eye development, and impaired fertility. The most appropriate interpretation is that gene demonstrates:

44 Two recessive mutations, and , affect the same visible trait. In a trans arrangement, progeny include wild-type recombinants at a frequency of . Which conclusion is most justified?

45 A woman with blood group A has a mother with blood group O. She has children with a man of blood group B whose mother had blood group O. What fraction of their children is expected to have blood group O?

46 A child is blood group AB and Rh-negative. The mother is blood group A, Rh-positive, and the father is blood group B, Rh-positive. Which parental genotypes are required for this child?

47 In a species with an XX-XO system, females are XX and males are XO. A nondisjunction event during meiosis in a female produces an egg containing two X chromosomes. If this egg is fertilized by a normal male gamete, the resulting offspring will most likely be:

48 A recessive X-linked disorder is carried by a woman whose father was affected and whose mother was homozygous normal. She has children with a normal man. What is the probability that a randomly selected child will be an affected son?

49 A father expresses an X-linked dominant trait, while the mother does not carry the allele. Which inheritance pattern is expected among their children?

50 A trait is sex-limited: allele is required for the trait, but the phenotype is expressed only in males. A heterozygous male is crossed with a homozygous recessive female. Assuming equal sex ratios, what fraction of all offspring will express the trait?

51 In a sex-influenced trait, allele is dominant in males but recessive in females. A heterozygous male and a heterozygous female mate. Which outcome is expected?

52 In a sex-influenced trait, allele is dominant in males but recessive in females. A heterozygous male and a heterozygous female mate. Which outcome is expected?

53 Two heterozygous individuals are crossed for three independently assorting genes, each showing complete dominance. What is the probability that an offspring will display the dominant phenotype for exactly two of the three traits?

54 A testcross produces observed progeny counts of , , , and for four expected classes in a ratio. What is the approximate chi-square value?

55 A genetic cross gives observed counts of dominant and recessive offspring. Under a hypothesized ratio, what is the correct conclusion at the significance level with degree of freedom?

56 A genetic cross gives observed counts of dominant and recessive offspring. Under a hypothesized ratio, what is the correct conclusion at the significance level with degree of freedom?

57 A mutation changes a codon from to . What type of molecular consequence is most directly produced?

58 A single-nucleotide deletion occurs near the beginning of a protein-coding sequence and changes every downstream codon until a premature stop codon appears. This mutation is best classified as:

59 A chromosome segment ABCDEFG becomes ABEDCFG after rearrangement. Which structural mutation is represented?

60 A researcher wants to generate a large collection of random point mutations throughout a plant genome while preserving chromosome structure as much as possible. Which treatment is most appropriate?