Developmental Genetics

Flashcards of key vocabulary terms and definitions from the Developmental Genetics lecture.

rosy gene (ry)

A common selectable marker in P-element mediated transformation, used to identify transgenic flies by their red eyes.

OX513A

A GM mosquito line developed by Oxitec scientists containing a fluorescence gene from marine coral and a lethality gene.

tTAV

The lethality gene in OX513A GM mosquitoes; encodes a protein that blocks transcription of genes essential to mosquito development.

Tetracycline

Acts as an antidote to the tTAV protein by binding to it and preventing it from blocking transcription of essential genes.

Totipotent

Cells capable of forming any tissue or cell type in the animal, and all genes have the potential to be expressed; in vertebrates, such cells are called embryonic stem cells.

Pluripotent

Cells that can give rise to many but not all cell types, found in a number of adult tissues, and retain their ability to develop into a range of specialized cells to replenish those that are lost.

Pattern Formation

Describes the events that organize the differentiating cells of an embryo to establish the body-plan axes (anterior–posterior, dorsal–ventral, left–right).

Morphogens

Substances whose presence in differing concentrations directs developmental fates.

Induction

When a cell induces its neighbors to acquire a certain fate.

Organizer

Transplanted region of an embryo that has the ability to induce formation of a second body axis.

Inhibition

If a cell prevents its neighbors from adopting a certain fate, the process is called inhibition.

Competence

In order for a cell to be able to respond to a signal from a neighbor. A cell must express the appropriate receptor for the signal

Symmetric Cell Division

When a cell divides, and the daughter cells inherit the same set of transcription factors and chromatin states that existed in the original cell.

Asymmetric Cell Division

When daughter cells inherit distinct subsets of factors present in the original cell.

Instars

The three larval stages of the Drosophila life cycle.

Syncytium

Multinucleate cell; in early Drosophila embryogenesis, nuclear divisions occur without any cytoplasm division, producing a multinucleate syncytium.

Coordinate Genes

Affect the entire axis formation of the embryo (also known as maternal effect genes).

Gap Genes

Mutants are missing large contiguous sections of the body.

Pair-Rule Genes

Mutants are missing parts of adjacent segment pairs in alternating patterns.

Segment Polarity Genes

Defects affect patterning within each of the 14 segments.

Homeotic Genes

Defects alter identity of one or more segments.

Maternal Effect Genes

Encode products that the mother supplies to the egg to influence embryonic development; the genotype of the mother determines the phenotype of the zygote.

Zygotic Genes

Involved in developmental processes; these are transcribed in the zygote or embryo; the genotype of the embryo determines the phenotype.

Bicoid

A maternal gene that plays a major role in establishing the A-P axis in Drosophila; mRNA is anchored to the anterior region of the egg and translated after fertilization to produce an A-P protein gradient; acts as a morphogen.

Hunchback

Is zygotically transcribed, under control of bicoid, but is also maternally provided as mRNA.

Caudal

Patterning the posterior of the embryo, it is repressed by Bicoid in the anterior.

Realizator Genes

Target genes of Hox genes whose expression contributes to the characteristic features of each segment.

Homeobox

A sequence of 180 nucleotides shared by Hox genes that encodes a 60–amino acid DNA-binding domain called the homeodomain.

Homeodomain

60–amino acid DNA-binding domain containing a motif (helix-turn-helix) previously recognized in transcription factors in bacteria and phage encoded by the homeobox.

Antennapedia Complex

Consists of genes: labial, Deformed, Sex combs reduced, proboscipedia, and Antennapedia; these act in combination to specify the head (cephalic) and thoracic parasegments

Bithorax Complex

Consists of the genes Ultrabithorax (Ubx), abdominal-A (abd-A), and Abdominal-B (Abd-B); expressed in overlapping sets of thoracic and abdominal parasegments, with sharp anterior boundaries and diffuse posterior boundaries.

Posterior Dominance

More posterior Hox gene products act as repressors of anterior genes (epistatic regulation).

Distal-less

Realizator gene imp for appendage formation. Required for appendage formation; expressed in head and thoracic segments but not in the abdomen;.

Trithorax

Mutations produce phenotypes like LOF Hox mutations.

Polycomb

Mutations resemble GOF Hox gene mutations.

Polycomb group (PcG)

Protein complex repressed target gene expression by recruiting protein complex that deacetylate (HDAC) and methylate (HMT) histones (H3K27-heterochromatin)

Trithorax (Trx)

Protein complex maintain active gene expression by recruiting protein complexes that acetylate (HAT) and demethylate (HDMT) histones (H3K27-euchromatin)

C. elegans

A nematode that exists as male (X0) or hermaphrodite (XX) and is a useful model organism in developmental biology.

Dauer Larva

A dormant state with low metabolic rate that C. elegans can enter if conditions are not favorable for development, and can develop to L4 larva once conditions improve.

Vulval Precursor Cells (VPCs)

Six cells from which the vulva forms during the last larval stage in C. elegans.

Lateral Inhibition

After reception of the lin-3 inductive signal, second signal is sent from the 1° cell, which inhibits neighboring cells from adopting the 1° fate.

Evo-Devo

The study of evolution of development.

Shh

Sonic hedgehog; a key patterning molecule and homolog of fly hh (hedgehog); a segment polarity gene and morphogen that establishes borders between cell compartments.

Apical Ectodermal Ridge (AER)

Directs outgrowth of the limb bud by responding to signals produced in mesenchyme cells toward the posterior side of the bud known as the zone of polarizing activity

Zone of Polarizing Activity (ZPA)

Acts as an organizer and promotes digit formation at the ends of the limb buds through Sonic hedgehog (Shh).

Polydactyly

The condition of having extra digits, often resulting from ectopic Shh signals.