cell proliferation

-cells divid by mitosis and cytokinesis

time location and amnt of cell dividing is regulated

programmed cell death

timing, lcoation, and mont of cell death are regulated

 3 types of differential expansion

(cell movement)

-cells move past one another w/in a block of animal cells causing drasing shape changes in the embryo

-certain cells break awa from a block of animal cells and migrate to a new location

-plant cells can divid along certain planes and expand in specific directions, causing dramatic changes in shaper

Cell differentiation

-undifferentiated cells specialize @ specific times and places in a stepwise fashion

-cells that do not undergo differentiation = stem cells

-many plant cells are capable of de-differentiating

Cell-cell interation

-embryonic cells divide, die and grow mor or differentiate in response to signals from other cells

proliferate

to divide and created more cells

-timing and extent=tightly controlled

what is responsible for cell proliferation in eukaryotes?

-mitosis and cytokinesis

-->cells initate mitosis via reg protein MPF

-->each stage of cycle has checkpoint

-->social controls/signals from other cells determine if cells continues to grow or not

meristems

(in plants)

-tissues present in same locations in embryonic and adult plants and perform the same function

-give rise to stems/roots/leaves/flowers etc

-undifferentiated cells that keep proliferating throughout life

stem cells

(animals)

-juveniles/adults they are found in specific locations where they proliferate to replace skin/blood/gut cells that die, repair wounds, create constant supply of diseas fighting cells in immune system

Apoptosis

(programmed cell death)

-due to signals from other cells; HIGHLY regulated

-occurs as certain tissues and organs take shape

(ALS-lou gehrig's disease)

Cell movement/growth 

in ANIMALS

-REGULATED cell movement = KEY

-cells move to new location in order for normal development to occur (give rise to germ cells; pigment containing cells; precursosr sor blood cells, nerve cells)

-most dramatic cell movement during early processes (post rapid cell division)

-gastrulation

gastrulation

cells in difff parts of mass rearrange themselves into 3 layers

(give rise to gut, skin, and other parts)

Cell movement/growth

in PLANTS

-Differential cell growth = KEY

-->cells do NOT need to move but do change ORIENTATION of cell divisions (controls direction of cell movement and growth)

-cells incased in stiff cell walls and do not move

-directionality of cell division and cell expansion carefully regulated

differentiating

-the process of becoming a specialized type of cell

-progressive, step by step process

-meristematic/stem cells-most become committed to certain cell fater EARLY in development and later become differentiated

-->look and behave like a specific cell type

de differentiating

only in PLANT cells

-can change their structure and function even after the cells have been specialized

totipotent

-plant cells capable of de-differentiating

"all powerful"

***difference btwn animal and plant cells***

Importance of cell-cell interactions

-involve sending and recieving signals

-cells change activity in response to these signals

-signal transduction pathways trigger the production of transcription factors

-signals change patterns of gene expression-->thus embryonic cell's structures and behavior

(fate of cell relies on signals it recieves from other cells)

Are all plant cells genetically equivalent?

YES

-cell de-differentiation must require genes for all types of cells not just one

-complete new individuals can be produced from a small section of root/shoot

-all plant cells contain same genes

Are all animal cells genetically equivalent?

YES

-proved through nuclear transfer

DOLLY-removed mammary gland cells; grew in culture; fused w/eggs that nuclei removed

**Identical to mammary gland**

-clone :genetic copy

How does differential gene expression occur?

-eukaryotic cells control gene expression @ several different levels:

-chromatin remodeling

-chromtin modification

-transcription regulation

-alternative splicing of mRNAs

-selective destruction of mRNA's

-translational rate

-activation/deactivation of proteins after they were translated

Transcriptional

Control

-responsible for differentiation

-controlled by regulatroy transcription factors (in eukaryotes)

Regulatory Transcription Factors

-influence chromatin remodeling and bind to promoter proximal elements, enhancers, silencer, or other regulatory sites in DNA

4 axes that determine cell fate

1-time (organisms current stage of development)

+ 3 spatial demensions (3 body axis)

1.-antierior/posterior (head/tail)

2.- ventral/dorsal (belly/back)

3.-left/right

pattern formation

-used to describe the events that determine the spatial organization of an embryo

(what becomes antierior/posterior/dorsal/ventral/right/left via what signals are sent)

-is a progressive process (signals repeat and each time they specify finer and finer control over what the cell becomes)

-early signals act as MASTER REGULATORS that set up general location

Bicoid

-"two tailed"

-gene's product provide prositional information

-bicoid genes codes for signal that telss cell where they are located along the anterior-posterior body axis

in situ hybridization

-to find where bicoid mRNAs are located in embryos

-found mRNA highly localized at anterior end

-when mRNA are translated, the protein product forms a steep [ ] gradient

-->bicoid protein is abundent in the anterior end but declines to progressively lover [ ] in the posterior end

-bicoid protein is a regulatory transcription factor

-[ ] of bicoid tells where you are in body

bicoid protein

-regulatory transcription factor

-binds to DNA and activates genes required for the formation of anterior structures

Importance of [ ] bicoid

[ ] of bicoid tells where you are in the body

HIGH [ ] = anterior (head)

LOW [ ] = posterior (tail)

Difference in master regulators btwn plants and animals

Bicoid = TRANSCRIPTION facto

auxin = hormone********

Auxin

-hormone

-enters cells and triggers the production of transcription factors that afect differentiation

-produced in meristematic cells at tip (apex) of growing embryo and is transported towards the base (roots)

-HIGH [ ] = top of shoot

-Low [ ] = base of roots

hormone

-signaling molecule that travels through the body and acts on distant target cells

Morphogens

-molecules that provide spatial info during early embryonic development, via [ ] gradient

-bicoid (animals-fruit fly)

-auxin (plants)

segment

-region of an animal body that contains a distinct set of structures and is repeated along its lenght

3 types of segmentation genes

1- gape genes

2- pair-rule genes

3- segment polarity genes

Gap Genes

-expressed 1st, in broad regions along the head/tail axis

-define general position of segments (what part of the body the segments are in)

-organize cells into groups of segments long anterior/posterior axis

Pair Rule Genes

-expressed 2nd

-altering bands

-pattern and order of expression suggests that pair rule genes demarcate the edges of individual segments

-organize cells into individual segments

segment polarity genes

-expressed last

-more restricted bands

-they delineate boundaries w/in individual segments

-establish anterior/posterior gradient w/in each segment

Homeotic genes

-products identify each segment's structural role

-trigger the development of structures that are appropriate to each type of sement

ex-Hox genes

Hox Genes

 -homeotic genes 

-expressed in distinctive pattern along the anterior/posterior axis in early embryos and control formation of segment specific structures

-occur in almost every animal; # varies though

-when altered by mutations, defects in patern formation results

**genes in HOX complexes of animals are homologous**

Homeosis

-replacement of one structure by another

-occurs when cells get incorrect infor about where they are in the body

Effector genes

change proliferation, death, movement and differentiation of cells

Master Regulator

-establsihes anterior/posterior gradient of embryo

-trigger the production of other regulatory signals and transcription factors, which trigger production of another set of signals and regulatory proteins and so on

process from undifferentiated to differentiated cell

Undifferentiated

-master regulator

-gap genes

-pair-rule genes

-segment polarity genes

-homeotic genes

-effector genes

Differentiated

MADS box genes

-in PLANTS

-analogous to homeotic genes of animals

How are regulatory transcription factors and cell-cell signals active in many ways/

-reg proteins and signals are CONSERVED & REUESD

-multicellular organisms --> have common signals, signal-transduction pathways, and regulatory proteins that are used OVER & OVER during development

-can create diff structures b/c each deployed @ diff TIMES and LOCATION

foundation of evolutionary change

-genetic changes altering developmental process in reg singals and cascade

Evo-devo

-evolutionary development

-focuses on understanding how changes in deveopmentally impt genes lead to evolution of new phenotypes