Deck 18: Organelle Inheritance and the Evolution of Organelle Genomes

Question 1

Use of double mutants has been invaluable in studying developmental pathways. In C. elegans, sex is determined by the ratio of sets of autosomes to X chromosomes. A diploid male has one X, and diploid hermaphrodites have two X's. The loss- of- function gene her- 1 produces XO worms that are hermaphrodites, but XX worms are unaffected. Mutation of a second gene, tra, causes the XX to develop as male. Given this information, what would be the phenotype of a tra, her- 1 double mutant?

A) lethality
B) a hermaphrodite
C) an intersex variant
D) a male nematode
E) a female nematode

Answer 1

D

Question 2

In Drosophila, a developmental mutation called ssa (spineless aristapedia) results in flies with mini leg parts on the antennae. What kind of gene does this mutation affect?

A) a gap gene
B) a homeotic gene
C) a maternal effect gene
D) a segment polarity gene
E) a pair- rule gene

Answer 2

B

Question 3

The abdominal segments of Drosophila have no appendages. Loss of function of bithorax genes results in appendages forming in these abdominal segments. Therefore, .

A) bithorax normally activates a gene that negatively regulates appendages in the abdomen
B) bithorax mutations are necessarily recessive
C) ultrabithorax usually acts to oppose bithorax genes
D) bithorax genes normally activate appendage- forming genes
E) expression of bithorax wild- type genes suppresses all appendage formation

Answer 3

A

Question 4

Suppose that a homeotic gene from Drosophila is introduced into an Arabidopsis embryo that has a pre- existing mutation in one of its homeotic flower genes. What effect would you expect and why?

A) a mixture of roughly equal numbers of Drosophila and plant gene product, producing an intermediate phenotype
B) expression of the Drosophila homeotic gene correcting the mRNA of the mutant plant
C) no effect, because Hox genes are different from MADS box genes
D) correction of the sequence in the mutant by recombination with the Drosophila gene sequence
E) rescue (or negating) of the phenotype of the mutant because the fly Hox gene supplies the missing protein

Question 5

Polycomb group (PcG) gene mutants cause ectopic expression of Antennapedia (Antp) and other homeotic genes. The PcG protein encoded by the PgG gene has a domain that binds to methylated histone H3. This finding supports which of the following hypotheses?

A) that PcG activates Antp genes in tissues
B) that PcG binds to Antp genes and serves as a transcription activator
C) that PcG mutants lack Antp mRNA compared to the wildtype
D) that PcG is allosteric activator of RNA polymerase II
E) that PcG repress transcription by interacting with chromatin

Question 6

There is much controversy in the news-both scientific and popular-about the use of embryonic stem cells for research. These cells are grown as cell lines in culture, created by taking the inner cell mass from 5- day- old embryos. What is the center of the controversy?

A) the unproven usefulness of stem cells to treat human disorders
B) the difference of opinion about whether these embryos are persons
C) the knowledge that these cell lines have reverted spinal cord injuries in mice
D) the fact that the embryos are mostly those unused by in vitro clinics
E) the realization that these cells are pluripotent rather than totipotent

Question 7

Since mice embryos with loss- of- function Hox mutations result in homeotic alterations, then introduction of such a mutation might cause _ _.

A) pointed rather than rounded ears
B) behavioral alterations causing limb shaking
C) a change in fur coloration along the dorsal midline
D) paralysis of hindlimbs but not forelimbs
E) ribs on normally rib- less vertebrae

Question 8

What is the name of the Drosophila multinucleated cell formed early in development?

A) blastoderm
B) syncytium
C) meristem
D) homeobox
E) blastocoel

Question 9

Mutations of regulatory elements of developmental genes may have either dominant or recessive effects. If a mutation deletes a silencer upstream of a HOX gene, which do you expect?

A) a dominant trans effect on both alleles of the HOX gene
B) a dominant effect in which cis HOX gene activity is up- regulated
C) a dominant effect which down- regulates HOX gene activity
D) a recessive effect in which cis HOX genes are down- regulated
E) a recessive effect in which cis HOX genes are up- regulated

Question 10

A pair- rule gene in Drosophila called runt controls nervous system formation. In the mouse, runt controls blood cell formation and genital structures. In humans, the analog of runt, when mutated, causes children to lack collar bones, and the opening at the top of the skull fails to close. What kind of experiment could tell you whether these genes are conserved in function?

A) sequencing the proteins encoded for by each of the species' runt genes
B) an in vivo experiment that replaces the coding sequence of Drosophila runt gene with the coding sequence from the homologous mouse runt gene to see if the mouse gene allows the nervous system to develop.
C) use of immunological methods to identify the target cells of the species' runt transcription factors
D) an in vitro experiment that identifies the DNA binding sites of the Drosophila runt gene.
E) sequencing of the runt genes from each of the three species

Question 11

Many mutations in the bithorax gene are known, such as postbithorax, contrabithorax and bithoriaxoid. Each mutation has a different effect on development of the reduced wing- like T3 appendage, the haltere. None of these mutations occurs in the coding sequence of bithorax, instead, where are these mutations and how do they effect development?

A) These mutations each effect silent sites and effect the stability of the bithorax mRNA.
B) Bithorax is inhibited by zygotic genes from the mother and these mutations affect maternal genes.
C) These mutations alter the slice sites for bithorax and affect the splicing of the bithorax mRNA. Their different effects on development are cause by affects on alternative splicing.
D) Each mutant alters a different codon within the bitorax gene, which affects the DNA- binding behavior of the bithorax protein.
E) These mutations each effect a different enhancer(s) near the bithorax gene and the resulting misexpression of bithorax in each mutant causes patterning defects in the haltere.

Question 12

Drosophila mutations such as bcd, if homozygous in the mother, produce offspring with lethal defects, no matter what the genotype of the offspring. For some other genes, the mutant phenotype can be "rescued" by introducing a wild- type allele into the embryo. What is the reason for these different outcomes?

A) Non- rescuable mutations are of paternal origin.
B) bcd is a Hox gene.
C) Rescuable mutations act as dominants.
D) Rescue requires recombination between the maternal and introduced alleles.
E) bcd is a maternal effect mutation.

Question 13

As a Drosophila larva molts and becomes a pupa, most of the larval tissues die and adult structures are formed from cells in clusters known as imaginal discs that have remained unchanged throughout the larval stages. Therefore, the disc cells are .

A) embryonal
B) zygotic
C) differentiated
D) maternal
E) transcriptionally activated

Question 14

Human Hox genes are in four clusters: HOXA, HOXB, HOXC, and HOXD, for a total of 39 genes. Besides conserving the clustering of genes, evolution has also conserved .

A) their chromosomal locations
B) the order of the genes within the clusters
C) their bilateral symmetry
D) their expression along the dorsal- ventral axis
E) the number of HOX genes

Question 15

In early vertebrate embryonic development, a number of pathways, such as Wnt, Hedgehog, and Notch, regulate differentiation and organ formation. They operate by .

A) establishing anterior- posterior and dorsal- ventral symmetry
B) regulating the expression of MADS box genes
C) cell signaling mediated by receptor binding
D) transcription activation due to interaction among transcription factors
E) repressing translation of developmental RNAs

Question 16

In an organism such as a sea urchin, administration of actinomycin D prevents all mRNA synthesis. However, early development up to gastrula formation can take place in the presence of actinomycin D but gastrulation cannot. This implies that .

A) actinomycin D is part of the normal environment of a sea urchin and serves as a developmental signal molecule
B) maternal effect genes regulate development until gastrulation
C) mRNA synthesis is not required after gastrulation
D) development beyond gastrulation requires actinomycin D
E) immature sea urchin embryos produce actinomycin D to regulate further development

Question 17

An Antennapedia (Antp) mutant in Drosophila has legs in place of antennae. This is caused by .

A) the interaction of an inhibitor gene of the bithorax complex with the Antp mutation
B) transcription of the Antp gene in the head region instead of in the thorax
C) loss of function of the Antp gene
D) a chromosomal error that shifts this Antp gene to the anterior end of the complex
E) the product of a head segment gene being over- expressed in the head

Question 18

Segmentation genes in Drosophila act in which of the following orders?

A) pair- rule, segment polarity, gap genes
B) pair- rule, segment polarity, Hox genes
C) pair- rule, transdeterminal, gap genes
D) gap, pair- rule, segment polarity
E) segmental, helical, spherical

Question 19

Aniridia is a human condition in which the eye has no iris. The protein encoded by the gene responsible for aniridia is very nearly identical to the protein product of the fly Eyeless protein. What experiment could provide evidence that the two genes are functionally equivalent?

A) Introduce the aniridia mutation into Drosophila embryos to look for iris formation.
B) Sequence the Eyeless and aniridia DNA sequences and regulators.
C) Use the Eyeless mRNA as a probe in other invertebrate and non- mammalian species.
D) Introduce the mouse aniridia wild- type sequence into the fly egg to see whether mouse eyes develop.
E) Replace the fly eyeless gene with the coding sequence of the mouse aniridia gene. Look for rescue compared to an eyeless gene mutant.

Question 20

Which of the following is not a mechanism of differentiation?

A) induction
B) nuclear migration
C) inhibition
D) apoptosis
E) morphogen secretion

Question 21

Hunchback protein occurs along a gradient, where the anterior embryo has high protein levels and the posterior has low levels, yet the hunchback mRNA is found at the same concentration throughout the embryo. These observations suggest that hunchback must be regulated post-

Question 22

During the evolution of development in animals, it is found that many regulatory genes have been co- opted for the development of different structures, such as limbs or digits. This is an example of what current area of research?

Question 23

In the development of C. elegans, an embryo of 1090 cells then loses 131 cells due to what process?

Question 24

Cells called influence development by controlling other cells in their local environment?

Question 25

You are interested in the homeobox genes that may regulate the development of the common clover plant Trifolium subterraneum. To identify clones of the T. subterraneum genome that contain these homeotic genes, you would probe with a rice gene that contains what domain?

Question 26

Certain mutations in non- Hox genes actually produce homeotic mutants due to a failure to modulate chromatin acetylation appropriately. This influence on cellular "memory" is called what?

Question 27

Null mutations in _ genes would be expected to result in the failure to establish the anterior- posterior poles of an embryo

Question 28

What term describes the process by which a cell acquires a certain fate from its neighboring cell?

Question 29

Cell signaling during much of C. elegans development occurs along concentration gradients. What kind of signaling does this represent?

Question 30

Flower homoeotic genes encode: .

A) morphogen genes
B) pair- rule genes
C) MADS box genes
D) housekeeping genes
E) homeobox genes

Question 31

A homeotic mutant flower has an arrangement (from outside in) of carpels, stamens, stamens, carpels instead of the usual sepal, petals, stamens, carpels. In general, Class A genes specify sepals, Class A and B genes specify petals, Class B and C genes specify stamens, and Class C specifies carpels. This mutant must therefore have a mutation in .

A) a Class A gene
B) a Class B gene
C) a Class C gene
D) both A and B
E) both B and C

Question 32

Which group of genes in Drosophila embryos must be mutated if the result is elimination of a significantly sized, contiguous region of segmentation?

Question 33

What substance, in different concentrations, directs developmental fates?

Question 34

The Antennapedia complex and the bithorax complex of genes all encode transcription factors that have a 180- bp DNA- binding domain. What is this domain called?

Question 35

If a cell from the blastoderm of the Drosophila embryo is committed to form the sixth abdominal segment of the adult and this cell is transplanted into the thorax- committed region of another embryo, will it develop properties of a thoracic or an abdominal segment?

Question 36

Holoprosencephaly is a highly variable condition in mammals, including humans. Its effects range from an absence of brain areas, mid- face disorders, and cyclopia to slight dental abnormalities. One form, HPE3, is caused by null mutations in Shh. Familial cases are inherited as a dominant trait. Which of the following do you expect?

A) HPE3 individuals also share a common environmental exposure.
B) HPE3 expression is modified by genetic background.
C) All mutations in Shh that result in HPE3 are due to frameshifts.
D) HPE3 is actually a multigene complex.
E) Each type of malformation is due to a different HPE3 allele.

Question 37

Homeotic genes in virtually all animals are said to show colinearity between the spatial arrangement of the tissues they act on as well as what other feature?

Question 38

An embryonic stem cell has the potential to differentiate into any cell or tissue type. Is it differentiated, pluripotent, or totipotent?

Question 39

Cell autonomous genes affect only those cells in which they are expressed. Which group of early developmental genes are not cell autonomous?

Question 40

A highly conserved protein domain of 60 amino acids, the homeodomain, is found in a large number of animals. This domain the proteins that have them to bind to what?

Question 41

Describe the genetic evidence that demonstrates that a developmental gene has maternal effect.

Question 42

Use a description of C. elegans development to distinguish clearly between differentiation and determination.

Question 43

Mouse eye genes can be inserted into Drosophila and can regulate the flies' eye formation. Differences in the size of horses are controlled by a gene also found to influence size variation in zebrafish. What do these examples illustrate?

Question 44

How can transplantation and ablation be used to find out if a cell in the source of a developmental signal?

Question 45

Describe aspects of plant and animal development that are shared and then give specific evidence that plants and animals independently evolved mechanisms of multicellular development?

Question 46

In Drosophila and other animals, Hox genes encode transcription factors that control development; but in Arabidopsis, a different family of transcription factors is produced with a different set of conserved amino acids. These are encoded by what group of genes?

Question 47

In Arabidopsis thaliana, a model organism in plant genetics, there are three classes of genes that control the development of floral structures: A, B, and C. Mutations of these genes cause organs to form in inappropriate places. What category of genes are they?

Question 48

Which structure in plants acts most like embryonic stem cells in animals?

Question 49

Genes that influence development in a manner that is independent of their paternal genotype are said to have effect.

Question 50

If a cell is no longer able to differentiate into any type of tissue, it has become .

Question 51

Epistasis analysis in single and double mutants, such as in the genes specifying genital development in C. elegans has helped to identify genes that function in developmental
.

Question 52

Most of the genes controlling development encode either signal molecules or .

Question 53

Molecules whose concentration and position in an embryo determine some aspect of development are called .

Question 54

How and when does the Antennapedia complex change antennae into legs?

Question 55

Certain species of lilies, if eaten by pregnant ewes, can cause the ewes to produce lambs with severe birth defects because the cyclopamine that the plant produces can block embryonic response to Shh. This type of birth defect is a phenocopy of mutations in which genes?

Question 56

Coordinate genes in an organism such as Drosophila determine the _ of the early embryo.

Question 57

A mutation in a fly causes an antenna to develop where a leg should be. This is an example of a mutation.

Question 58

In limb- positioning in tetrapods, the acts as an organizer to promote digit formation at the distal ends of limb buds.