Foundations of Biology Exam 5: Chapter 21

differentiation

the process by which an unspecialized cell becomes a distinct specialized cell type; usually by changes in gene expression; acquires specialized properties

differential gene expression

expression of different sets of genes in cells with the same genome; responsible for creating different cell types

genetic equivalence

when all different cell types of a multicellular individual posses the same genome

de-differentiate

the process of reversing the normal course of cell specialization; can be induced to create pluripotent stem cells (iPS cells)

clone

a genetically identical copy

Dolly the sheep

mammory gland cells removed from a white faced sheep, are in a lab, and fused with a de-nucliated egg of a black faced sheep created this white faced clone

somatic cell nuclear transfer (SCNT)

a method to create embryos or entire animals in which a nucleus taken from a non-reproductive call is transferred into an oocyte (immature egg cell) that has had its nucleus removed; the genes of the somatic cell nucleus that direct development of the oocyte; success rate for this is low

control of transcription and regulation of chromatin condensation

the two most important eukaryotic cell gene expression regulation factors for differentiation

epigenetic inheretance

the cornerstone of how an embryonic cell differentiates into a particular cell type and remains that type of cell

principles common to development in every mutlicellular organism

1. divide

2. cells signal what they are doing, and what type of cell that are going to be

3. begin to express certain genes rather than others

4. move, expand, or contract in specific directions

5. in the case of some cells, die

cell division

in order for an embryo to grow it must divide; equally as important, the timing, location, extent, and sometimes orientation must be tightly controlled; regulated by cell checkpoints, MPFs, and "social controls" from other cells

cell-cell interactions

cell interact constantly during development (signaling molecules) that drive behaviors foundational to development; most signals are recieved on the surface of developing embryos and are relayed through signal transduction cascades

signal transduction cascade

TFs are activated and patterns of gene expression change in a cascade; embryo cell activaties altered: may divide, differentiate, move, change shape, or die

cell differentiation

most embryonic cells acquiring specialized properties as they mature; at crucial points, the signals recieved by embryonic cells specifiy their fate

fate

the type of adult cell or structure that normally forms from an embryonic cell or structure during that course of development

cytoplasmic determinants

a regulatory molecule affecting development; it is distributed unevenly in a cell, therefore, if the plane of cleavage is controlled, this is transmitted to one daughter cell but not another, specifying the fate of the cell that obtains the development; this mechanism is often used in insects, rarely mammals, and almost never in plants

induction

a mechanism used by all organisms that determines the fate of a cell during development; involves a signal from one cell determining what another cell will become during development

default pathway

the pathway followed by a cell that does not recieve an inducing signal that changes its cell fate

gastrulation

the process of coordinating cell-shape changes and movements, including the movement of some cells from the outer surface of the embryo to the interior that results in the formation of the three germ layers and establishes the axes of the embryo

programed cell death

regulated cell death that is used in development, tissue maintenance, and destruction of infected cells; can occur in different ways, apoptosis is best known

apoptosis

the predominant programmed cel death in animal cells during development; a series of tightly controlled changes in cellular activity that leads to the self-distruction of a cell; occurs frequently during embryological development and as a part of the immune response to remove infected or cancerous cells; most common programmed cell death

the body plan

the position of different body parts in three dimensions

the three body axes

1. anterior (toward the head) to posterior ( toward the tail)

2. dorsal (toward the back) to ventral (toward the belly)

3. left to right

different signaling molecules are present at different concentrations along each of these to help cells "learn" where they are in a developing embryo

pattern formation

the series of events that determines the spatial organization of an entire embryo or parts of an embryo; if a molecules signals that a target cell is in a specific axis, then that molecule is involved in that; many exist in a concentration gradient

morphogen

a molecule that exists in a concentration gradient and provides information to embryonic cells; in most organisms, they play a role in setting up body axises

larva

an immature form of an animal species in which the immature and adult stages have different body forms

mother

in most insects, the genes from the ______ are responsible for setting up the embryo's body axes

maternal effect mutations

a mutation in a female parent that alters the offspring without causing an obvious mutated phenotype in the parent; is explained by altering cytoplasmic determinants that control embryonic development that are placed in the egg by the female

segments

a well-defined region that is repeated along the anterior-posterior body axis of an animal; arise in early development and produce characteristic body structures such as wings, legs, and antennae

bicoid

two-tailed, mutation that replaced anterior segments that form the head and thorax with misshapen segments that are normally found in the posterior end of larvae

in situ hybridization

a technique for detecting specific DNAs and mRNAs in cells by use of labeled complementary probes; can be used to determine where and when particular genes are expressed in embryos, fluorecence (FISH) makes the labeled molecule glow

genetic regulatory cascades

a set of regulatory genes that are linked in such a way that ones initially activated gene triggers the expression of other regulatory genes, which in turn triggers the expression of yet more regulatory genes; often used to control development

genetic regulatory cascade for Drosphila

1. maternal effect

2. gap genes

3. pair-rule genes

4. segment polarity genes

5. hox genes

6. effector genes

hox genes

a class of genes found in most animal phyla, including vertebrates, that are expressed in a distinctive pattern along the body axes in development and control formation of specific structures; code for TFs with a DNA-binding sequence called a homeobox

homeotic mutations

a mutation that causes one body part to be substituted for another Hox genes homeotic; contain a homeobox

homeobox

a DNA sequence of about 180 base pairs that code for a DNA-binding region in the resulting protein; genes with this usually play a role in controlling development of organisms

order

the order of the hox genes along the chromosome corresponds to the _______ of where the genes are expressed along the anterior-posterior axis

homologus

the genes in hox clusters of animals are ________ for almost all animals

homologus

similarity among organisms of different species due to shares ancestry

conserved

key insight: key molecular mechanisms of pattern formation have been highly _______ during animal evolution

same

during development, the _______ regulatory genes and signal molecules are often used over and overs in a variety of contexts

major

the context in which a signal molecule is sent and recieved- its location, timing, and intensity- has a ______ effect on the signals meaning and consequences

tool-kit genes

a set of key developmental genes that establishes the body plan of animals and plants; present at the origin of the multicellular lineages and elaborated upon over evolutionary time by a process of duplication and divergence; includes hox genes

evo-devo

a research field focused on how changes in developmentally important genes have led to the evolution of new phenotypes, especially body forms

heterometry

altering quantity of gene expression of a developmental gene; ex. this caused the changes in finch beaks

heterochrony

altering timing of gene expression of a developmental gene; ex. giraffe necks growing longer than humans

heterothrophy

altering spatial pattern of gene expression of a developmental gene; ex. ducks having webbed feet due to no apoptosis