The presence of the disease sickle cell anemia illustrates that natural selection does not always eliminate ________ alleles.
A. neutral
B. recessive
C. polymorphic
D. dominant
Answer: B
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A scientist is investigating a hormone response in rose bush stems by removing the apical meristems of the main stems. What is the most likely result of this experiment and what hormone is responsible?
A. New apical buds will develop under the influence of auxin. B. Larger, deeper roots will form under the influence of cytokinin. C. More leaf buds will appear along the main stems under the influence of auxin. D. Flowers will turn yellow and fall off under the influence of auxin. E. Lateral buds will develop under the influence of cytokinin.
Duplicated chromosomes result in two sister chromatids that are held together by a centromere. Which of the following statements best describes the location of genes along these sister chromatids?
A. Sister chromatids have identical alleles but are located in different locations along each sister chromatid because of crossing-over during meiosis. B. Sister chromatids have identical genes, but different alleles. These are located in the same location on each sister chromatid. C. Sister chromatids have identical genes, but different alleles. Additionally, they are located in different locations along each sister chromatid because of crossing-over during meiosis. D. Sister chromatids have identical alleles that are located in the same place along each sister chromatid.
Hybridization between populations upon secondary contact may result in ________
A) reinforcement of the two original species by way of pre- or post-zygotic isolating mechanisms B) the creation of one or more new species as hybrids between the two parental species C) the creation of a hybrid lineage that has higher fitness than either of the parental species D) All of the above are possible. E) None of the above are possible.
Many genes encode proteins that are always needed by a cell, and therefore are always expressed. Such genes are
known as: a. repressible. b. promoter. c. constitutive. d. inducible. e. operons.