Deck 22: Developmental Genetics and Immunogenetics

Question 1

Epigenetic changes in development are important in that the gene expression of cells that make up a particular organ or tissue type is often defined by epigenetic markers. Which of the following epigenetic regulations is known to cause more long-term gene silencing during the course of development?

A) chromatin remodeling
B) DNA methylation
C) histone modifications
D) DNA ubiquitination

Answer 1

B

Question 2

Activin is a protein that normally exists in a gradient within certain tissues in developing embryos. Certain undifferentiated cells cultured without activin produce epidermal cells. However, activin induces these same cells to adopt other fates (e.g., blood, muscle, heart), depending on the concentration of activin. Based on these observations, activin acts as a(n):

A) transcription factor.
B) cell-surface receptor.
C) morphogen.
D) second messenger.
E) activator.

Answer 2

C

Question 3

Which of the following groups of genes is directly regulated by egg-polarity genes?

A) homeotic genes
B) gap genes
C) Hox genes
D) pair-rule genes
E) segment-polarity genes

Answer 3

B

Question 4

The proteins Dorsal and Bicoid both act as morphogens in Drosophila embryogenesis. However, the establishment of the concentration gradients of each protein differs. Which of the following statements CORRECTLY describes this difference?

A) The dorsal gene is transcribed maternally while the bicoid gene is transcribed in the developing embryo.
B) The dorsal gene is transcribed in the developing embryo whereas the bicoid gene is transcribed maternally.
C) The concentration gradient of Dorsal is established through asymmetric subcellular localization whereas the concentration gradient of Bicoid is established through selective degradation.
D) The concentration gradient of Dorsal is established through asymmetric subcellular localization whereas the concentration gradient of Bicoid is established through asymmetric localization of the bicoid mRNA and thus protein.
E) The concentration gradient of Dorsal is established through differential rates of translation whereas as the concentration gradient of Bicoid is established through a transport system.

Question 5

Which of the following statements about homeotic genes is INCORRECT?

A) Homeotic genes were first identified in invertebrates, but their homologs were found in almost all organisms.
B) All homeotic genes contain consensus sequences that result in a specific DNA-binding motif.
C) In vertebrates, homeotic genes are organized into two distinct clusters.
D) All homeotic genes encode transcription factors that direct further gene expression.
E) Homeotic genes exhibit a relationship between their order on the chromosome and the timing of their expression.

Question 6

Which specific group of genes specifies the identities of individual body segments?

A) segmentation genes
B) gap genes
C) homeotic genes
D) pair-rule genes
E) segment-polarity genes

Question 7

When animals like Dolly the sheep are cloned using techniques that transfer a nucleus from a donor animal into the egg of a recipient animal, is the resultant clone genetically identical to the nuclear donor animal?

Question 8

Use the following to answer questions
In the late 1940s Edward Lewis discovered mutations in the Antennapedia gene that lead to legs developing on the head of a fly instead of antenna. These mutations are dominant and lead to ectopic expression of the Antennapedia gene.
Certain mutations in the Antennapedia gene can lead to antenna developing in a mesothoracic segment where legs should have developed. What characteristics would you expect from this class of mutations? (Select all that apply.)

A) They are loss-of-function.
B) They are recessive.
C) They are gain-of-function.
D) They are dominant.
E) They result in ectopic Antennapedia expression.

Question 9

Use the following to answer questions
In the late 1940s Edward Lewis discovered mutations in the Antennapedia gene that lead to legs developing on the head of a fly instead of antenna. These mutations are dominant and lead to ectopic expression of the Antennapedia gene.
Based on these data, how would you expect the gene to be expressed in the mutant? (Select all that apply.)

A) in every segment
B) in a more anterior segment
C) in a more posterior segment
D) earlier
E) later

Question 10

Which of the following statements about Hox genes is INCORRECT?

A) All Hox genes found in organisms other than Drosophila have a conserved pattern of identical clustered arrangements.
B) When a vertebrate Hox gene is moved to a new location within the Hox gene complex, the timing of its expression is altered.
C) The Hox genes encode transcription factors that help to determine the identity of the body region.
D) They are usually organized as clusters and the order on the chromosome is important for their expression pattern.
E) The recent studies suggest the role of miRNA in controlling the expression of some Hox genes.

Question 11

List the five major classes of developmental genes in Drosophila in the order (earliest to latest) that they regulate development.

Question 12

Which of the following choices lists the CORRECT sequence of gene expression during Drosophila development? 1. Segmentation genes
2) Egg-polarity genes
3) Homeotic genes

A) 1, 2, 3
B) 2, 3, 1
C) 2, 1, 3
D) 3, 2, 1
E) 3, 1, 2

Question 13

What have the cloning experiments in plants and animals confirmed with regard to developmental processes?

Question 14

Briefly describe when and how Dolly the sheep was cloned.

Question 15

What are Hox genes?

Question 16

Which of the following pairing of genes and developmental processes is INCORRECT?

A) bicoid and nanos-anterior posterior axis
B) antennapedia complex-head and anterior thoracic segment
C) cactus and toll-dorsal development
D) hunchback-ventral development
E) bithorax complex-posterior thoracic and abdominal segment

Question 17

Which of the following is the CORRECT order of gene groups expressed in normal Drosophila development? 1. Gap genes
2) Homeotic genes
3) Pair-rule genes
4) Segment-polarity genes
5) Egg-polarity genes

A) 1, 2, 3, 4, 5
B) 4, 2, 5, 1, 3
C) 3, 1, 2, 5, 4
D) 5, 2, 4, 3, 1
E) 5, 1, 3, 4, 2

Question 18

The Bicoid protein in fruit flies specifies anterior development. In the absence of Bicoid protein in an egg, the embryo will develop two tails. The bcd^- mutation is recessive and exhibits a maternal effect. Which of the following CORRECTLY describes the embryos produced from a cross between a bcd⁺/ bcd^- male and a bcd^-/bcd^- female?

A) All embryos will be normal.
B) All embryos will have two tails.
C) Three-fourths of the embryos will have two tails.
D) One-half of the embryos will have two tails.
E) One-fourth of the embryos will have two tails.

Question 19

The product of the bicoid gene is critical for the establishment of _____ structures in the Drosophila embryo.

A) anterior
B) posterior
C) dorsal
D) ventral
E) segment

Question 20

Which of the following genes determines the identity of individual segments during development?

A) bicoid
B) nanos
C) cactus
D) disheveled
E) dorsal

Question 21

What are homeotic genes and what do they do?

Question 22

What are the role and relationship of egg-polarity genes, segmentation genes, pair-rule genes, gap genes, and homeotic genes in Drosophila development?

Question 23

Describe the epigenetic changes that occur in cells during development and the role they play in differentiation of cell types within a multicellular organism.

Question 24

The loss of a tadpole's tail during amphibian metamorphosis and the separation of the digits in human hands during embryonic development are caused by:

A) necrosis.
B) autophagy.
C) cellular digestion.
D) apoptosis.
E) morphogenesis.

Question 25

Regulation of apoptosis involves initial activation of the enzymes called _____, which act as proteases that can trigger a cascade of cellular protein degradation, bringing about eventual DNA fragmentation.

A) apaptase
B) acetylase
C) demethylase
D) nucleases
E) caspases

Question 26

Use the following to answer questions
The diagram below illustrates the normal expression of three different groups of genes (A, B, and C) within four different whorls of a developing flower. Normally, whorl 1 produces sepals, whorl 2 produces petals, whorl 3 produces stamens, and whorl 4 produces carpels. Furthermore, expression of class A genes inhibits class C genes, and expression of class C inhibits class A.
What kind of mutation would produce sepals in all four whorls?

A) defective in A
B) defective in B
C) defective in C
D) defective in A and B
E) defective in B and C

Question 27

What is apoptosis?

A) autophagy
B) a process that generates the anterior-posterior axis
C) antibody production
D) genetic maternal effect
E) programmed cell death

Question 28

In wild-type flowering plants, carpel development is determined by what class of gene products?

A) A gene products
B) A + B gene products
C) B + C gene products
D) C gene products
E) A + C gene products

Question 29

Use the following to answer questions
The diagram below illustrates the normal expression of three different groups of genes (A, B, and C) within four different whorls of a developing flower. Normally, whorl 1 produces sepals, whorl 2 produces petals, whorl 3 produces stamens, and whorl 4 produces carpels. Furthermore, expression of class A genes inhibits class C genes, and expression of class C inhibits class A.
What would be the identity of the four whorls if gene B was ectopically expressed in whorls 1 and 2?

A) sepals, petals, stamens, and carpels
B) petals, petals, petals, petals
C) petals, petals, stamens, stamens
D) stamens, carpels, stamens, carpels
E) sepals, petals, sepals, petals

Question 30

Use the following to answer questions
The diagram below illustrates the normal expression of three different groups of genes (A, B, and C) within four different whorls of a developing flower. Normally, whorl 1 produces sepals, whorl 2 produces petals, whorl 3 produces stamens, and whorl 4 produces carpels. Furthermore, expression of class A genes inhibits class C genes, and expression of class C inhibits class A.
What kind of mutation would produce sepals in whorls 1 and 4 and petals in whorls 2 and 3?

A) defective in A
B) defective in B
C) defective in C
D) defective in A and B
E) defective in B and C

Question 31

The insect hormone ecdysone is known to trigger apoptosis during metamorphosis that turns larva into adult structures. Which of the following experiments would confirm the activation of apoptosis by ecdysone?

A) Inhibition of rpg and hid gene via RNAi should result in excess cells that would normally be eliminated.
B) Overproduction of rpg and hid genes via constitutive promoter should prevent the full metamorphosis.
C) Inhibition of receptor binding to ecdysone should result in excess apoptosis.
D) Overproduction of ecdysone receptor should result in inhibition of rpg and hid genes.
E) Inactivation of grim should result in elimination of excess number of cells.

Question 32

A flower is made up of four concentric rings of modified leaves called whorls. Which of the following lists the individual whorls in CORRECT order going from the outside toward the inside of the flower?

A) petals, sepals, carpels, and stamens
B) sepals, petals, stamens, and carpels
C) carpels, stamens, petals, and sepals
D) stamens, carpels, sepals, and petals
E) carpels, petals, sepals, and stamens

Question 33

The following diagram describes the genetic regulation of flower development in angiosperms. In each box, write the class of gene, and below write the flower structures determined by those gene(s).

Question 34

Use the following to answer questions
The diagram below illustrates the normal expression of three different groups of genes (A, B, and C) within four different whorls of a developing flower. Normally, whorl 1 produces sepals, whorl 2 produces petals, whorl 3 produces stamens, and whorl 4 produces carpels. Furthermore, expression of class A genes inhibits class C genes, and expression of class C inhibits class A.
What kind of mutation would produce carpels in whorls 1 and 4 and stamens in whorls 2 and 3?

A) defective in A
B) defective in B
C) defective in C
D) defective in A and B
E) defective in B and C

Question 35

What are morphogens, and what do they do?

Question 36

Use the following to answer questions
The diagram below illustrates the normal expression of three different groups of genes (A, B, and C) within four different whorls of a developing flower. Normally, whorl 1 produces sepals, whorl 2 produces petals, whorl 3 produces stamens, and whorl 4 produces carpels. Furthermore, expression of class A genes inhibits class C genes, and expression of class C inhibits class A.
What kind of mutation would produce sepals in whorls 1 and 2 and carpels in whorls 3 and 4?

A) defective in A
B) defective in B
C) defective in C
D) defective in A and B
E) defective in B and C

Question 37

The genes that determine flower development were divided into three classes by Meyerowitz and his colleagues: class A, class B, and class C. What would the flowers produced by a plant with a mutation in a class B gene look like?

Question 38

What is the function of segmentation genes and homeotic genes in Drosophila?

Question 39

(a) Explain briefly the roles of Bicoid and Nanos proteins in determining the anterior-posterior axis of the fruit-fly embryo. (b) Explain how the Bicoid and Nanos protein gradients are established in the fruit-fly embryo. (c) Bicoid mutant embryos lack head structures and instead have structures at the anterior end of the embryo that are characteristic of the posterior end. Propose an explanation of this phenotype.

Question 40

During development, cells can respond to the presence of hormones and other signals with changes in gene expression that can bring about cell differentiation. In most cases, the differentiated state needs to be maintained through subsequent cell divisions and long after the inducing signal has disappeared. Describe a mechanism that can maintain the differentiated state after the inducing signal has disappeared.

Question 41

What is an autoimmune disease?

Question 42

The development of the nematode worm C. elegans is highly reproducible. During development of the hermaphrodite, 1090 somatic cells are generated, but only 959 somatic cells are found in the mature adult. What is the MOST likely explanation for the change in cell number given its reproducibility?

A) inhibition of genes that stimulate cell division
B) activation of genes that inhibit cell division
C) apoptosis of cells during development
D) necrosis of cells during development
E) stochastic variations in cell division

Question 43

What is meant by the phrase "ontogeny recapitulates phylogeny"? Is this an accurate statement?

Question 44

Which of the following characteristics of vaccines are required in order for them to be effective in immunization? (Select all that apply.)

A) They must contain the entire pathogen.
B) They must present antigenic surfaces recognized by immunoglobulin molecules.
C) They must stimulate lymphocyte activity.
D) They must stimulate the production of large quantities of plasma cells.
E) They must stimulate the production of memory cells.

Question 45

Why do you think the mutation rate in immunological genes is unusually high?

Question 46

Use the following to answer questions
In the nematode worm C. elegans loss-of-function ced-3 mutations lead to more cells than normal due to a defect in apoptosis. Loss-of-function mutations in ced-9 cause embryonic lethality due to ectopic cell deaths. The phenotype of ced-9; ced-3 double mutants is the same as ced-3 single mutants; that is, there are more cells than normal due to a defect in apoptosis. Genes ced-3 and ced-9 are known to act in the same genetic pathway.

-Which of the following pathways is consistent with the genetic data?

A) ced-3 $\rightarrow$ ced-9
B) ced-9 $\rightarrow$ ced -3
C) ced-3 ced-9
D) ced-9 ced-3

Question 47

List at least two processes involved in apoptosis that are controlled by caspases.

Question 48

The eyeless gene in fruit flies, Small eye gene in mice, and Aniridia gene in humans have high homology in DNA sequence and their mutations result in defects in eye development. Which of the following statements is NOT consistent with this observation?

A) The same genes in distantly related organisms can shape similar developmental pathways.
B) The eyes of insects and mammals must have evolved independently during evolution.
C) A common pathway underlies eye development in all three organisms.
D) All three genes evolved from a common ancestral sequence.

Question 49

A lymphocyte pool plays a role in which process?

A) self-antigen generation
B) clonal selection
C) antibody production
D) genetic maternal effect
E) major histocompatibility complex (MHC) recognition

Question 50

What three sets of proteins are required for immune responses?

Question 51

What is the role of the major histocompatibility complex (MHC) in tissue-graft rejection?

Question 52

Which of the following mechanism does NOT contribute to the diversity of antibody and T-cell receptors recognizing different antigens?

A) junctional diversity
B) somatic hypermutation
C) somatic recombination
D) pairing of different light and heavy chains
E) pairing of different MHC loci

Question 53

The primary function of differentiated B lymphocytes within the vertebrate immune system is to produce:

A) cytotoxic chemicals.
B) hormones.
C) antibodies.
D) ROS.
E) complements.

Question 54

Which of the following statements accurately describes the organization of the immune system?

A) Humoral immunity centers around the production of specialized T cells that can mount an attack on cells that express foreign MHC.
B) Cellular immunity involves specialized lymphocytes called B cells, which mature in the bone marrow.
C) The primary immune response results in generation of memory cells, which allows the body to mount a more effective attack upon repeated exposure to the same antigen.
D) The theory of clonal selection supports the presence of a large pool of lymphocytes that get engaged in attacking one specific antigen.
E) Autoimmune disease is specifically referring to the self-destructive behavior of T cells mounting an attack on other T cells, which leads to a compromised immunity.

Question 55

Use the following to answer questions
In the nematode worm C. elegans loss-of-function ced-3 mutations lead to more cells than normal due to a defect in apoptosis. Loss-of-function mutations in ced-9 cause embryonic lethality due to ectopic cell deaths. The phenotype of ced-9; ced-3 double mutants is the same as ced-3 single mutants; that is, there are more cells than normal due to a defect in apoptosis. Genes ced-3 and ced-9 are known to act in the same genetic pathway.
Which of the following statements might be TRUE about the genes ced-3 and ced-9? (Select all that apply.)

A) ced-3 encodes a caspase.
B) ced-9 encodes a caspase.
C) ced-9 encodes a functional homolog of the Drosophila gene reaper.
D) ced-3 stimulates phagocytosis of a cell in which it is expressed.
E) ced-9 activity leads to DNA degradation.

Question 56

What are some of the different signals that can initiate programmed cell death (apoptosis)?

Question 57

What is apoptosis? Describe the important roles that apoptosis plays during development of an organism. Provide specific evidence that apoptosis is important to normal development.

Question 58

What is the difference between apoptosis and necrosis?

Question 59

Which of the following statements accurately describes antibodies?

A) Kappa and lambda are the two types of immunoglobulin heavy chains.
B) Genes coding for antibody constant regions undergo somatic recombination to generate diversity.
C) Antigens are always proteins that are exposed on the surface of foreign invaders.
D) Antigen-binding sites are located at the tips of the two arms of the Y-shaped antibody.
E) The variable region segments (V genes) are only subjected to somatic recombination to contribute to different antigen recognition as they come in direct contact with antigens.

Question 60

Xenotransplantation involves transplanting tissues or organs from one species to another. Some medical researchers are exploring the possibility of transplanting pig organs into humans to address the worldwide human organ donor shortage. What strategies might help with the success of such transplantations? (Select all that apply.)

A) Create transgenic pigs that lack a sugar molecule that humans do not have for use as organ donors.
B) Inject human organ transplant recipients with a sugar molecule from pigs that they do not have prior to transplantation.
C) Treat pigs with immunosuppressive drugs prior to harvesting their organs for donation.
D) Treat human organ transplant recipients with immunosuppressive drugs following xenotransplantation.
E) Administer pig bone marrow to the human organ transplant recipient prior to transplantation.

Question 61

(a) In what sense does each person's immune system become adapted to that person's environment and to the set of antigens to which that person is exposed? (b) Explain in terms of the clonal selection theory how a person's immune system responds to and comes to be "adapted" to the person's environment and personal exposure to antigens.

Question 62

How do lymphocytes violate the general principle that all cells in an organism contain the same set of genetic information?

Question 63

Distinguish between the genetic mechanisms used to generate antibody diversity within a person's immune system and those used to generate MHC antigen diversity between different individuals.