Introduction to Bi 102 Pass out Syllabus & Homework. Go over syllabus and schedule.syllabus Go over Homework 1.Homework 1
The Need for Cell Division During development – One fertilized egg cell begins to divide – Develops into a mature multicellular organism In adults – To repair damage – To replace worn out tissue
Stages of the Cell Cycle Before a cell can divide: – Key cellular components must be duplicated Proteins, membranes, and organelles –Chromosomes must be duplicated Complete set of genetic information –Ensures that the new cells can survive
The Cell Cycle (eukaryotes): Mitosis Interphase cytokinesis
Interphase has 3 phases: G1 Phase or Gap 1: Longest phase Cell growth, Proteins/lipids synthesized, Prepares for replicating DNA G1 Start after cell division
Interphase: S Phase G1 S DNA Synthesis (Chromosomes/ chromatin Replicated)
Interphase: G2 Phase G1 S G2 Prepares for cell division, proteins made Mitochondria replicate Centrioles replicate Microtubule synthesis
Mitosis: Nuclear division Microtubules separate chromosomes G1 S G2 Mitosis
Cytokinesis: Cell division, divides into 2 daughter cells Cell may renter cell cycle Or leave cell cycle (G0) G1 S G2 Mitosis Cytokinesis G0
G 0 Phase Most cells are not actively dividing These cells are in G 0 phase –Can leave cell cycle for days to years – Some cells will divide again; e.g. liver cells – Some cells stay in G 0 ; e.g. nerve cells
Interphase – G1, S, & G2 Phases
Mitosis: Prophase
Mitosis: Metaphase 1.Microtubules grow, connect to centromeres, 2.and align the chromosomes
Mitosis: Anaphase 1.Sister chromatids separate, move to opposite poles. 2.Microtubules shorten & pull them in.
Mitosis: Telophase 4 1.Chromosomes at poles 2.Nucleus reforms 3.Chromosomes unwind into chromatin 4.Spindle degraded
Cytokinesis 1.Cytokinesis follows mitosis. 2.In animal cells, actin filaments (protein) pinch the cell in two. 3.Seen as a cleavage furrow on the cell membrane. 4.Plant cells divide by growing a new cell wall (cell plate) between the 2 nuclei.
DNA Synthesis DNA Synthesis & Replication: DNA “unzips” Two opposite strands separate Matching bases are added to each side Result: Two copies of the original DNA molecule