Transcript Timing and Development of Growth

Timing and Development of Growth
Big Idea 2E: Many bio processes involved in
growth, reproduction, and homeostasis include
temporal regulation and coordination
Essential Knowledge
• 2E1: Timing and coordination of specific events
are necessary for the normal development of
an organism, and these events are regulated by
a variety of mechanisms.
• 2E2: Timing and coordination of physiological
events are regulated by multiple mechanisms.
All Cells in an Organism Contain Same DNA
• Came from same zygote dividing
over and over again
DNA Review
• 1 molecule of DNA
forms a chromosome
• Each chromosome
contains many
segments of DNA called
a gene
• 1 gene codes for one
polypeptide (portion of
a protein)
• Only about 1% of DNA
consists of genes
Gene Expression
• DNA in nucleus is
transcribed into
RNA
• RNA exits nucleus
and is translated
into a polypeptide
by ribosomes
Control of Transcription
• Enzyme that transcribes DNA (RNA Polymerase)
requires transcription factors
• Activation of transcription factors triggers
transcription, thus expressing the gene.
Cells Are Different Because they
Express Different Genes
• Each cell generates different proteins and at
different times
• Very complicated, focus of research currently
During Development Different Genes Are Expressed
• Homeotic genes control developmental patterns and
sequences  Determine where each body part develops
Messing with homeotic changes
researchers got legs to grow instead of
antennae in flies
Embryonic Induction
• As cells develop and mature, they cause other
cells to express certain genes
• Ex: as eye forms, one cell causes others to
express genes necessary to make eye cells
• Allows each cell to develop at correct time
For Plants…
• Temp and water availability determine seed
germination and embryo growth.
All Cells Originally Can Be Anything!
• But over time processes (DNA methylation/ induction)
restrict what genes are expressed
• When new cells form they usually have same genes shut
off as parent cell
DNA methylation shuts off many genes!!
Genetic Mutations and Development
• Minor mutations in homeotic genes or
others can have hugely detrimental effects
on development
MicroRNAs
• Regulatory molecule that blocks translation of
RNA
• Controls development and cellular organization
Apoptosis
• Programmed cell death
• As orgs grow, some cells must be destroyed
• A normal process in cell differentiation.
Originally
there are
cells
between
your
fingersthey die,
separating
the
fingers