1. Timing and Development of Growth
Big Idea 2E: Many bio processes involved in growth, reproduction, and homeostasis include temporal regulation and coordination

2. 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.

3. All Cells in an Organism Contain Same DNA
Came from same zygote dividing over and over again

4. 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

5. Gene Expression DNA in nucleus is transcribed into RNA
RNA exits nucleus and is translated into a polypeptide by ribosomes

6. Control of Transcription
Enzyme that transcribes DNA (RNA Polymerase) requires transcription factors
Activation of transcription factors triggers transcription, thus expressing the gene.

7. Cells Are Different Because they Express Different Genes
Each cell generates different proteins and at different times
Very complicated, focus of research currently

8. During Development Different Genes Are Expressed
Homeotic genes control developmental patterns and sequences  Determine where each body part develops

9. Messing with homeotic changes researchers got legs to grow instead of antennae in flies

10. Allows each cell to develop at correct time
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

11. For Plants…
Temp and water availability determine seed germination and embryo growth.

12. 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

13. DNA methylation shuts off many genes!!

14. Genetic Mutations and Development
Synpolydactyly (SPD) is a genetic disorder that results from mutations in one of the HOX genes. The phenotypes are shown in the pictures below, which usually involves developmental disorders in the fingers and toes resulting in fusion and malformation.
Minor mutations in homeotic genes or others can have hugely detrimental effects on development

15. MicroRNAs Regulatory molecule that blocks translation of RNA
Controls development and cellular organization

17. Apoptosis Programmed cell death
As orgs grow, some cells must be destroyed
A normal process in cell differentiation.

18. Originally there are cells between your fingers- they die, separating the fingers