Question: In plants, genes E, F, and G are on one chromosome arm. Alternate dominant and recessive alleles of all three genes determine visible traits: E = normal leaf number, e = extra leaves, F = normal stems, f = furry stems, G = normal flower size, g = giant flowers. A plant that is heterozygous for an inversion involving all three genes is crossed to a plant with extra leaves, furry stems, and giant flowers. The arrangement of alleles is shown in the diagram. If you look at thousands of offspring of this cross, what phenotypes do you expect to see?
Answer Options:
• A) Most, but not all, offspring will either be normal for all three traits or have extra leaves, furry stems, and gigantic flowers.
• B) Half of the offspring will be normal for all three traits and half will have extra leaves, furry stems, and giant flowers.
• C) Due to crossovers between E and F in parent 1, a small number of offspring will have only extra leaves, or only furry stems and giant flowers.
• D) Due to double crossovers between E and F and F and G, a very small number of offspring will have only furry stems, or only extra leaves and giant flowers.
• E) Due to crossovers between F and G, a small number of offspring will have only extra leaves and furry stems, or only giant flowers.
Answer: A) Most, but not all, offspring will either be normal for all three traits or have extra leaves, furry stems, and gigantic flowers.
Question: Which can result in Down syndrome?
Answer Options:
• A) nondisjunction resulting in an extra chromosome 21
• B) deletions of a segment of chromosome 21
• C) having the triploid number of chromosomes
• D) a reciprocal translocation between acrocentric chromosomes 14 and 21
Answer: A) nondisjunction resulting in an extra chromosome 21
Question: What is true about reciprocal translocation heterozygotes and inversions?
Answer Options:
• A) They are both used to make Balancer chromosomes.
• B) The amount of DNA in the genome remains the same.
• C) The genes at the boundaries may be disrupted, while those in the middle are most likely unaffected.
• D) Up to 50% of gametes may be unbalanced, resulting in semisterility.
Answer: D) Up to 50% of gametes may be unbalanced, resulting in semisterility.
Question: Which is a mechanism by which transposable element mobilization may be controlled by the cell?
Answer Options:
• A) synthesizing an enzyme that removes transposable elements from the genome
• B) blocking transcription of transposable element genes
• C) blocking translation of transposable element transcripts
• D) increasing the mutation rate of transposable element DNA sequences
• E) alternative splicing of transposable element transcripts
Answer: B) blocking transcription of transposable element genes
Question: On the island of Madeira, two populations of house mice have accumulated different Robertsonian translocations. Which are true about these two populations of mice?
Answer Options:
• A) They have fewer chromosomes than mice in other areas of the world.
• B) Mice from different populations are unable to mate with each other.
• C) They are becoming extinct because of semisterility.
• D) They are isolated from each other geographically.
• E) If mice from different populations mate, their offspring are sterile.
Answer: A) They have fewer chromosomes than mice in other areas of the world.
Question: What might result from movement of transposable elements in a species’ genome?
Answer Options:
• A) The level of expression of one or more genes could be changed.
• B) A gene could be moved from one chromosome to another.
• C) The rate of point mutation could increase.
• D) A segment of DNA could be duplicated or deleted.
Answer: A) The level of expression of one or more genes could be changed.
Question: In what way can defective transposable elements alter genomes even if they cannot mobilize?
Answer Options:
• A) Genes located between two transposable elements could be moved to a nonhomologous chromosome.
• B) Crossing-over between transposable elements on the same chromosome can result in a deletion or an inversion.
• C) Crossing-over between transposable elements on nonhomologous chromosomes can result in a reciprocal translocation.
• D) Proteins produced by the defective transposable elements introduce point mutations in other areas of the genome.
Answer: B) Crossing-over between transposable elements on the same chromosome can result in a deletion or an inversion.
Question: Which can result in Down syndrome?
Answer Options:
• A) inversion in chromosome 21
• B) nondisjunction resulting in an extra chromosome 21
• C) deletion of a segment of chromosome 21
• D) having a triploid number of chromosomes
Answer: B) nondisjunction resulting in an extra chromosome 21
Question: Triticale is an allopolyploid hybrid between wheat and rye. Some strains of Triticale show agricultural promise because
Answer Options:
• A) they combine the high yields of wheat with the ability to adapt to unfavorable environments like rye.
• B) the grain is high in protein, especially the amino acid lysine.
• C) they are sterile because the wheat and rye chromosomes cannot pair during meiosis.
• D) they combine desirable traits from wheat and rye in one crop plant.
Answer: A) they combine the high yields of wheat with the ability to adapt to unfavorable environments like rye.
Question: During evolution, the additional copies of genes resulting from whole genome duplication events in new species exhibit the following feature(s).
Answer Options:
• A) They are always lost.
• B) They may mutate beyond recognition.
• C) They may acquire new functions.
• D) They never undergo any change.
Answer: C) They may acquire new functions.
Question: How would you determine if a present-day species evolved from an ancestral species by whole genome duplication?
Answer Options:
• A) Present-day species will always be tetraploid.
• B) Genome sequence of present-day species reveals blocks of homologous gene sequences on two different chromosomes.
• C) Genome sequence of present-day species shows that within blocks of homologous gene sequences, the order of genes is mostly conserved.
• D) Genome sequence of present-day species shows that within blocks of homologous gene sequences, the order of genes is never conserved.
Answer: B) Genome sequence of present-day species reveals blocks of homologous gene sequences on two different chromosomes.