A. They have been lost during evolution, since the organelles no longer rely on DNA replication.
B. The required genes are kept in the nucleus, but many have evolved by gene transfer from the organelle.
C. These genes have undergone mutations and have changed beyond recognition, but are still present in the organelle.
D. The organelles do not replicate their DNA; they import new DNA from the nucleus.
E. The required genes are on plasmids that are separate from the organelle’s genome.
10.19 Based on the variation of genome size and gene number in the organisms presented in the following graph, which organism has the highest number of genes per unit length of their genome? (Note the logarithmic scale.)
A. H. sapiens
B. M. musculus
C. A. thaliana
D. C. elegans
E. E. coli
10.20 Which of the following groups of living organisms has the highest variation in haploid genome size?
A. Mammals
B. Fish
C. Fungi
D. Protozoa
E. Prokaryotes
10.21 All cells in a multicellular organism have normally developed from a single cell and share the same genome, but can nevertheless be wildly different in their shape and function. What in the eukaryotic genome is responsible for this cell-type diversity?
A. The genes that encode transcription regulatory proteins
B. The regulatory sequences that control the expression of genes
C. The genes that code for molecules involved in receiving cellular signals
D. The genes that code for molecules involved in sending cellular signals to other cells
E. All of the above
10.22 Didinium nasutum is a single-celled eukaryote that can hunt and feed on other living cells. It has an elaborate anatomy with beating cilia, a “mouth opening,” an “anal aperture,” and a set of contractile bundles; it can also shoot “darts” to paralyze its prey. What group of living cells does D. nasutum represent?
A. Protozoa
B. Yeasts
C. Algae
D. Animals
E. It can belong to any of the above
10.23 It is a model organism used to study various cell processes such as regulation of the eukaryotic cell cycle. Mutants are available for every gene in its exceptionally small genome. It can live indefinitely in either a haploid or a diploid state. Which of the following describes this organism?
A. It can reproduce only asexually.
B. It is a fungus.
C. It lacks a cell wall.
D. Its cell cycle is typically much slower than that of human cells.
E. All of the above
10.24 It is a model organism used to study various eukaryotic cell and developmental processes such as cell division and cell death. Its hermaphrodite adult is composed of exactly 959 somatic (non-germ) cells, the lineage of each of which has been worked out with great precision. It is approximately 1 mm long. Which of the following describes this organism?
A. It is a vertebrate.
B. It is a plant pathogen that destroys many crops.
C. Its genome codes for a few thousand genes.
D. It can fly.
E. It can be frozen indefinitely in a state of suspended animation.
10.25 It is a model organism used to study various cell and developmental processes such as the growth of developing body parts in the right place and with the correct shape. It develops from a fertilized egg to an adult in a little over a week, and has been a favorite of geneticists for almost a century. Some of its cells have giant chromosomes whose banding patterns have been extremely helpful in classical genetic studies. Which of the following describes this organism?
A. It is a vertebrate.
B. Its genome is only 10 million nucleotide pairs long.
C. There are many more duplicate genes in this organism compared to humans.
D. Although useful for genetic studies, the molecular mechanisms governing its development are irrelevant to human development.
E. It normally only reproduces sexually.
10.26 This model organism is particularly well suited for studying developmental processes in higher animals. It develops from a fertilized egg to an adult in only two to three months, and its body is transparent for the first two weeks, making it easy to observe cell behavior during development. Which of the following describes this organism?
A. It is a vertebrate.
B. It is well suited for genetic analysis.
C. Its early stages of development occur outside of the mother’s body.