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

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

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 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

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 fingers- they die, separating the fingers