Exam 18: Developmental Genetics

What is the significance of the homeodomain?

During development,many genes act in such a way as to decrease the number of alternative developmental pathways that a cell can follow.Usually there are two alternative developmental paths for a cell to follow.What is the term given to genes that act in this fashion?

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

The bicoid gene of Drosophila generates embryos with two posterior regions.What is the likely aspect of embryonic development that the bicoid gene probably controls?

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

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.

What significant conclusion has the classic work on the eyeless and Pax6 genes provided in terms of developmental mechanisms?

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

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

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?

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.

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

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

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

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

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

Drosophila and Arabidopsis use different sets of nonhomologous master regulatory genes to establish the body axis and specify the identity of structures along such an axis.

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?

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

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