1. One striking result of many artificial selection experiments is the observati
ID: 53679 • Letter: 1
Question
1. One striking result of many artificial selection experiments is the observation that the mean value of a phenotypic trait can become altered beyond the range of variation present in the original population. This result can be mostly attributed to:
a. a change in gene regulation
b. chromosome rearrangement and increase in DNA content
c. mutation
d. change in allele frequency and recombination of alleles at different loci
e. population bottleneck
2. The hierarchical distribution of traits among animals, for example, chordate features such as the presence of a skull, jaws, and paired limbs, implies that
a. there has been a gradual increase in both the diversity and complexity of organisms over evolutionary time
b. organism have lost ancestral adaptations as they became modified to invade new environments
c. traits appeared sequentially over time, with each new trait acquired by a subgroup of animals with previous traits
d. animals with intermediate traits are expected to be rare in the fossil record
e. descent with modification has enabled animals to become better adapted over time
3. Which process leads to poor fitness when an organism is heterozygous for a chromosome inversion?
a. trans-regulatory elements do not function properly
b. DNA that is duplicated within the inversion creates an extra metabolic burden when a cell undergoes mitosis
c. chromosome inversions generally cause frame-shift mutations
d. crossing-over within the inversion creates gametes with both duplicated genes and missing genes
e. because harmful recessive alleles are shielded from selection in inversion heterozygotes, a large number of these sorts of defective alleles tend to accumulate in the population
Explanation / Answer
1) a
2) d
3) d
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