Deck 20: Developmental Genetics

Question 1

Which term refers to the regulatory events that establish a specific pattern of gene activity and developmental fate for a given cell?

A)lysogen
B)differentiation
C)determination
D)gradient regulated
E)attenuation

Answer 1

C

Question 2

Experiments involving nuclear transplantation in amphibians indicate that nuclei derived from blastula are more likely to support development of complete and normal adults compared with those derived from later stages of development.What do these experiments tell us about the process of development?

Answer 2

Development occurs as a series of cascades,with early genes influencing late genes,at times with stability.Such progressive determination,if stable,may be irreversible and fail to support development of an entire organism from a single cell.A number of epigenetic factors such as chromatin remodeling and DNA methylation are also likely to come into play.

Question 3

Explain the differences between differentiation and determination.Provide examples of each process and indicate how each is involved in development.

Answer 3

Determination is the early commitment of a cell to an eventual developmental fate.Differentiation is the set of functional and structural changes associated with the expression of that developmental fate.When nuclei of the developing Drosophila embryo reach the blastoderm stage,they become determined.Differentiation of the cells in Drosophila occurs during metamorphosis.Development,therefore,probably depends first on the determination of cells,then on the differentiation of cells.

Question 4

In Drosophila,the sequential order of the function of segmentation genes is ________.

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

Question 5

Mutations that eliminate a contiguous region in the Drosophila embryo's segmentation pattern are called ________.

A)homeodomains
B)gap genes
C)compartment genes
D)linkage genes
E)segment genes

Question 6

Three investigators-Nusslein-Volhard,Wieschaus,and Lewis-won the Nobel Prize for physiology and medicine in 1995 for work they did in 1970 with Drosophila.Briefly describe their findings.

Question 7

Immediately after fertilization of a Drosophila egg,the zygote nucleus undergoes a series of divisions.Subsequent nuclear migration generates a(n)________.

A)syncytial blastoderm
B)maternal effect
C)homeodomain
D)zygote
E)cleavage nucleus

Question 8

How does determination relate temporally to differentiation?

Question 9

Which function earlier in development: maternal-effect genes or zygotic genes?

Question 10

Define determination and differentiation.

Question 11

What kinds of general observations cause one to conclude that development is the result of variable gene activity?

Question 12

Maternal effects are cases of extrachromosomal inheritance in which the genotype of the mother influences the phenotype of her immediate offspring in a non-Mendelian manner.Provide a rationale for the molecular basis of a maternal effect.

Question 13

In Drosophila,what is the order of function of the segmentation genes?

Question 14

Provide a brief description of the variable gene activity hypothesis as it relates to development.What information is often provided in support of this hypothesis?

Question 15

Which general genetic process is believed to account for the variety of cellular structures and functions in eukaryotic cells?

A)variable gene activity
B)negative control exclusively
C)maternal environmental activities
D)intron processing
E)RNA processing

Question 16

How do segment polarity genes relate to pair-rule genes?

Question 17

It is often said that development is a two-step process.Which two steps are likely to be referred to here?

Question 18

Which of the following is a fundamental characteristic of the Notch pathway?

A)It works through nuclear signals involving the lac operon.
B)It works through direct cell-to-cell contact.
C)It allows mRNAs to accumulate in the posterior portion of the Drosophila embryo.
D)It directs mRNAs to antisense systems in the posterior portion of all organisms.
E)It provides symmetry to plant flowers.

Question 19

Design an experiment that would allow you to determine if a particular nucleus in a Drosophila embryo is capable of directing development of an entire new fly.

Question 20

Provide a brief description of segment polarity genes,including their regulation and their molecular and developmental effects.

Question 21

Differentiation is the process whereby a cell's determined state is expressed.

Question 22

A homeobox gene is one that produces a group of repetitive base sequences such as a VNTR.

Question 23

Give a brief definition of a homeobox.

Question 24

Molecular/structural orientations (gradients)in an egg are thought to play a significant role in development.What is the origin of such gradients? What evidence indicates that the maternal genotype is involved in providing such gradients?

Question 25

Determination is the process whereby a cell's eventual developmental fate is set.

Question 26

The bicoid gene of Drosophila generates embryos with two posterior regions.What aspect embryonic development does the bicoid gene control?

Question 27

What is the general order of genes involved in determining early Drosophila development?

Question 28

Mutations in the selector genes sometimes form structures in the wrong segment,transforming the antenna of a fly into a leg,for example.What are such mutations called?

Question 29

It is presently believed that the asymmetric distribution of substances in the egg,positioned by the mother,is responsible for establishing the determined state.Which general term describes such molecular positioning?

Question 30

Describe the relationship between the maternal-effect gene bicoid and the zygotic gene hunchback.

Question 31

In Drosophila,maternal-effect genes are influential in determining the anterior-posterior organization of the developing embryo.

Question 32

Do Hox gene clusters exist in humans? If so,how many are known to exist?

Question 33

From a human developmental standpoint,what is the significance of Hox genes?

Question 34

Segmentation genes,such as the pair-rule class,are inherited through mitochondrial DNA in Drosophila.

Question 35

Genetic involvement in development appears to be achieved,at least in part,by variable gene activity.

Question 36

A gene that specifies the fate of a particular anatomical segment in Drosophila is called a(n)________.

Question 37

Which class of genes controls the developmental identity of segments along the anterior-posterior axis?

Question 38

What is the significance of the homeodomain?

Question 39

Caenorhabditis elegans is extremely useful as an experimental organism because it has relatively few cells,and,for the most part,each embryonic cell's fate is developmentally fixed.