Genetics Problems and Exercises
Qualitative and Quantitative Traits
Problem 1
Statement: The phenotypic expression of qualitative features can be changed only by a mutation causing VF.
Answer: True
Problem 2
Statement: The phenotypic variation in a population for a qualitative trait is continuous. VF
Answer: False
Genotype-Environment Interaction and Hybrids
Problem 3
Statement: The genotype-environment interaction is not very specific, so it is easy to make euphenic changes. VF
Answer: False
Problem 4
Statement: Hybrid individuals are homozygous. VF
Answer: False
Gametes and Epistasis
Problem 5
Statement: The possible gametes of an individual with genotype AABBCC are:
a) ABC, aBC
b) AA, BB, and CC.
Answer: a) ABC
Problem 6
Statement: Epistasis is an example of the interaction between alleles of different genes. VF
Answer: True
Pleiotropy and Codominance
Problem 7
Statement: A gene is pleiotropic when it has multiple phenotypic effects. VF
Answer: True
Problem 8
Statement: Codominance in a hybrid shows an intermediate phenotype with respect to the parental purebreds. VF
Answer: False
Phenocopies and Albinism
Problem 9
Statement: Mice raised on a manganese-deficient diet show the same behavioral disorders as dancing mice. This is an example of:
a) Expressive
b) Phenocopy
Answer: b) Phenocopy
Problem 10
Statement: Albino mice are more fearful than pigmented mice. The allele that causes albinism has pleiotropic effects. VF
Answer: True
Genotypic Segregation and Mendel’s Laws
Problem 11
Statement: The genotypic segregation in the second filial generation of crossing two pure breeds is 1AA: 2AA: 1aa. VF
Answer: False (It should be 1AA: 2Aa: 1aa)
Problem 12
Statement: The principle of uniformity is met only when the parental generation is a homozygous dominant male parent and a homozygous recessive female parent. VF
Answer: False (It is met when both parents are homozygous, regardless of which is dominant or recessive)
Problem 13
Statement: Mendel’s third law is true only for linked genes. VF
Answer: False (It applies to independently assorting genes)
Problem 14
Statement: In the intersection of two dihybrids with the AaBb genotype, the 9/16 ratio appears in their offspring. VF
Answer: True
Homologous Chromosomes and Crossover
Problem 15
Statement: Two homologous chromosomes have identical alleles for all genes. VF
Answer: False (They can have different alleles)
Problem 16
Statement: Crossover is possible because, in the 1st meiotic prophase, homologous chromosomes lie parallel. VF
Answer: True
Problem 17
Statement: In a dihybrid individual for two linked genes in the repulsion phase, the gametes AB and ab are recombinant. VF
Answer: True
Meiosis and Genetic Recombination
Problem 18
Statement: In the 2nd meiotic anaphase, 2n chromatids separate to each pole. VF
Answer: False (It’s n chromatids)
Problem 19
Statement: Meiosis occurs in all body cells. VF
Answer: False (It occurs in germ cells)
Problem 20
Statement: Genetic recombination occurs only in linked genes. VF
Answer: False (It can also occur through independent assortment)
Problem 21
Statement: In the 2nd meiotic division, the sister chromatids that migrate to different poles can carry different genetic information. VF
Answer: True (Due to crossing over)
Linked Genes and Sex-Linked Traits
Problem 22
Statement: The progeny of a cross AaBb x aabb is 500AB, 100Ab, 500ab. These genes are:
a) Independent
b) Linked in coupling phase
Answer: b) Linked in coupling phase
Problem 23
Statement: A trait is said to be sex-linked when the genes that determine it are located in the differential portion of the sex chromosomes. VF
Answer: True
Monosomies, Polyploidy, and Mutation Rate
Problem 24
Statement: Monosomies exemplify polyploidy. VF
Answer: False (They are examples of aneuploidy)
Problem 25
Statement: The mutation rate is the same for all genes of a species. VF
Answer: False
Genetic Mosaicism and Duplication
Problem 26
Statement: An individual is a genetic mosaic if they have cells with different chromosomes. VF
Answer: True
Problem 27
Statement: Duplication is an example of a structural chromosomal abnormality. VF
Answer: True
Recessive Alleles and Crossover in Sex Chromosomes
Problem 28
Statement: Recessive alleles located in the differential portion of the Y chromosome are not manifested phenotypically. VF
Answer: False (They are always expressed in males)
Problem 29
Statement: There is never crossover between the X and Y chromosomes. VF
Answer: False (There can be crossover in the pseudoautosomal regions)
Problem 30
Statement: The two sex chromosomes in a woman are homologous for all their genes. VF
Answer: True
Colorblindness and Genetic Code
Problem 31
Statement: A normal male has a normal maternal grandmother, a colorblind maternal grandfather, a colorblind mother, and a normal father. His maternal grandmother is:
a) Homozygous
b) Heterozygous
Answer: b) Heterozygous
Problem 32
Statement: Because the genetic code is degenerate, there may be several transfer RNAs for the same amino acid. VF
Answer: True
RNA and Protein Synthesis
Problem 33
Statement: There is a relationship between the linear arrangement of nucleotides in messenger RNA and the linear arrangement of amino acids in proteins. VF
Answer: True
Problem 34
Statement: Because the two DNA strands are complementary, it is immaterial which one is copied to synthesize the messenger. VF
Answer: False (Only the template strand is transcribed)
Operon Model and Heritability
Problem 35
Statement: In the operon model, when the operator gene is locked, the structural genes cannot be transcribed. VF
Answer: True
Problem 36
Statement: When heritability is zero, selection procedures make no sense. VF
Answer: True
Karyotypes and Twin Studies
Problem 37
Statement: The karyotype 45, X0 is not feasible in humans. VF
Answer: False (It leads to Turner syndrome)
Problem 38
Statement: For any character, the expected correlation between monozygotic twins is higher than that expected for dizygotic twins. VF
Answer: True
Problem 39
Statement: A woman with the karyotype 47, XXY develops as a female. VF
Answer: False (This karyotype leads to Klinefelter syndrome, which affects males)
Pleiotropy and Normalizing Selection
Problem 40
Statement: Bastock’s studies with Drosophila Yellow individuals raised the possibility that the implicated allele produced smaller male reproductive success due to a chain of multiple phenotypic effects (pleiotropy). VF
Answer: True
Problem 41
Statement: Through normalizing selection procedures, it is possible to isolate strains of silly and listless rats. VF
Answer: False (Normalizing selection favors the average phenotype)
Biological Efficacy and Heterosis
Problem 42
Statement: The biological efficacy of an individual is measured by reproductive success. VF
Answer: True
Problem 43
Statement: The greater fitness of heterozygotes is called heterosis. VF
Answer: True
Allele Frequencies and Punctuated Equilibria
Problem 44
Statement: Allele frequencies can always be calculated from genotypic frequencies. VF
Answer: True
Problem 45
Statement: The fertile tetraploid hybrids obtained from two diploid species support the theory of punctuated equilibria. VF
Answer: False
Diversifying Selection and Natural Selection
Problem 46
Statement: When selection favors several optimal phenotypes in the population because it simultaneously favors the reproduction of individuals with maximum and minimum values, it is called:
a) Directional
b) Diversifying
Answer: b) Diversifying
Problem 47
Statement: Natural selection is independent of environmental factors. VF
Answer: False
Genealogy and Dominant Inheritance
The following genealogy shows dominant inheritance with complete penetrance and no new mutations:
(Insert genealogy image here)
Problem 48
Statement: Individual I1 is heterozygous. VF
Answer: True
Problem 49
Statement: Individual II2 is homozygous. VF
Answer: False
Problem 50
Statement: If I1 and I2 had a third child, the probability that they would express the trait is ¾. VF
Answer: True