biology 3

• endocrine signaling • paracrine signaling • juxtacrine signaling • reciprocal induction

hormones travel through the bloodstream to faraway target cells

signals diffuse to nearby cells

• cells must touch • one cells signal binds directly to receptors on another cell

• two tissues signal back and fourth causing both to differentiate

• movement of cells from one place to another • required for embryonic development and continues throughout life • errors can cause birth defects or embryo death

• signaling molecules trigger movement • actin filaments push the cell forward • actin interacts with myosin to contract and push the cell • chemical signals guide direction and speed • some cells move individually others move collectively like epithelial cells

• how many cell types a cell can become

• cane become almost any cell type • cannot form placenta • source of embryonic stem cells

can become several related cell types

can become a few cell types

can become only one cell type

can form an entire organism including placenta zygotę and early divisions

different genes are turned on or off

the same DNA

differential gene expression

• transcription (gene is copied into mRNA) • mRNA leaves the nucleus • translation - ribosome reads mRNA - tRNA brings amino acids - amino acids link tg • protein is made - the amino acid chain folds and becomes a protein

a methyl group (carbon w 3 hydrogens) is added to DNA, usually silencing or turning off the gene by blocking proteins needed for transcription

the control of gene expression that occurs without a change in the underlying DNA sequence

chemical changes to histone proteins that make DNA more or less accessible for transcription

• alter chromosome structure • make dna more or less accessible to RNA polymerase • can be inherited

copying DNA into RNA for gene expression

• where the information in a gene is used to make a functional product, usually a protein. Think of it like this • Your DNA is a cookbook. • A gene is one recipe. • Gene expression is when the cell actually uses that recipe.

• process where a cell uses mRNA to make a protein.