Biology 171 Flashcards (All)

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embryo

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A young developing organism; the stage after fertilization and zygote formation.

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apoptosis

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Series of genetically controlled changes that lead to death of a cell. Occurs frequently during embryological development and later may occur in response to infections or cell damage. Also called programmed cell death.

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gastrulation

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The process by which some cells on the outside of a young embryo move to the interior of the embryo, resulting in the three distinct germ layers (endoderm, mesoderm, and ectoderm).

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differentiation

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The process by which a relatively unspecialized cell becomes a distinct specialized cell type (e.g., liver cell, brain cell) usually by changes in gene expression. Also call cell differentiation.

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stem cells

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Any relatively undifferentiated cell that can divide to produce daughter cells identical to itself or more specialized daughter cells, which differentiate further into specific cell types.

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meristems

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In plants, a group of undifferentiated cells that can develop into various adult tissues throughout the life of a plant.

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differential gene expression

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Expression of different sets of genes in cells with the same genome. Responsible for creating different cell types.

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clone

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An individual that is genetically identical to another individual.

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regulatory transcription factor

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General term for proteins that bind to DNA regulatory sequences (eukaryotic enhancers, silencers, and promoter-proximal elements), but not to the promoter itself, leading to an increase or decrease in transcription of specific genes.

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anterior

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Toward an animal’s head and away from its tail. The opposite of posterior.

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posterior

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Toward an animal’s tail and away from its head. The opposite of anterior.

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ventral

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Toward an animal’s belly and away from its back. The opposite of dorsal.

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dorsal

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Toward an animal’s back and away from its belly. The opposite of ventral.

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pattern formation

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The series of events that determines the spatial organization of an embryo, including alignment of the major body axes and orientation of the limbs.

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segment

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A well-defined region of the body along the anterior-posterior body axis, containing similar structures as other, nearby segments.

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in situ hybridization

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A technique for detecting specific DNAs and mRNAs in cells and tissues by use of labeled probes. Can be used to determine where and when particular genes are expressed in embryos.

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segmentation genes

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A group of genes that affect body segmentation in embryonic development. Includes gap genes, pair-rule genes, and segment polarity genes.

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regulatory cascade

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In embryonic development, a progressive series of interactions among genes and/or cytoplasmic determinants that organizes the body plan of the embryo.

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homeotic genes

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Any gene that specifies a particular location within an embryo, leading to the development of structures appropriate for that location. Mutations in homeotic genes cause the development of extra body parts or body parts in the wrong places.

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homeosis

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Replacement of one body part by another normally found elsewhere in the body as the result of mutation in certain developmentally important genes (homeotic genes).

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Hox genes

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A class of homeotic genes found in several animal phyla, including vertebrates, that are expressed in a distinctive pattern along the anterior-posterior axis in early embryos and control formation of segment-specific structures.

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evo-devo

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Research field focused on how changes in developmentally important genes have led to the evolution of new phenotypes.

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gametes

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A haploid reproductive cell that can fuse with another haploid cell to form a zygote. Most multicellular eukaryotes have two distinct forms of gametes: egg cells (ova) and sperm cells.

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sperm

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A mature male gamete; smaller and more mobile than the female gamete.

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egg

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A mature female gamete and any associated external layers (such as a shell). Larger and less mobile than the male gamete. In animals, also called ovum.

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gametogenesis

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The production of gametes (eggs or sperm).

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acrosome

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A caplike structure, located on the head of a sperm cell, that contains enzymes capable of dissolving the outer coverings of an egg.

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cytoplasmic determinant

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A regulatory transcription factor or signaling molecule that is distributed unevenly in the cytoplasm of the egg cells of many animals and that directs early pattern formation in an embryo.

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yolk

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The nutrient-rich cytoplasm inside an egg cell; used as food for the growing embryo.

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centriole

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One of two small cylindrical structures, structurally similar to a basal body, found together within the centrosome near the nucleus of a eukaryotic cell.