The Cellular Basis of Inheritance All cells come from cells
Why do cells divide? • Cells must divide to replace cells that die and to repair tissues. • You are made of more than 200 trillion cells! Cells are constantly dying
2. Cells divide for growth and development Fertilized egg at first division
What are the purposes of Cell Division? 3. Reproduction (ASEXUAL)
The Organization of DNA • DNA is organized into GENES • GENES are organized into CHROMOSOMES • What is a Chromosome? • Chromatin? • The Genome?
What is a chromosome? A Chromosome has a centromere. It can be single or it can be duplicated.
Chromosome duplication and distribution during mitosis Words to Know: Chromatids Centromere Chromosome
S-phase The CELL CYCLE is the lifespan of a cell, and may include division. If the Cell cycle is 12 hours . . . S-phase- stands for DNA synthesis, lasts for 3 to 6 hrs G1 and G2 phase – stands for Gap phase G-phase
Cytokinesis – process by which cytoplasm is divided into 2 Mitosis – Actual division of nucleus Diagram of cell cycle
The Cell Cycle For most cells, 90% of the cell cycle is spent in Interphase. Suppose a cell is known to divide every 20 hours . . .
Nuclear envelope is present Nucleoli are present Chromosomes are diffuse chromatin. Chromosomes replicate Cells spend most of the cell cycle in this stage INTERPHASE
The Phases of Mitosis PROPHASE • The nucleoli disappear • Chromosomes condense • Mitotic Spindle begins to form • The nuclear envelope disappears
Early prophase Late prophase
The Phases of Mitosis METAPHASE • Chromosomes on metaphase plate (equator) • Sister chromatids attached to opposite poles by spindle fibers
The Phases of Mitosis ANAPHASE 1. Sister chromatids (now chromosomes) move toward the poles.
The Phases of Mitosis TELOPHASE • Nuclear envelope re-forms • Nucleolus re-forms • Chromosomes unwind • Daughter nuclei form • Cleavage furrow visible (cytokinesis)
CYTOKINESIS • Animal Cells: Cleavage Furrow forms • Plant Cells: Cell Plate forms Cytokinesis Cell plate
Where would we look for cells dividing rapidly? Animals: Blastulas
Interphase Prophase Metaphase Telophase Anaphase
Where would we look for cells dividing rapidly? Plants: Meristems
9.4TUMORS AND CANCER TUMOR TYPES • Benign Tumors • Not cancer • Do not spread from point of origin • Usually easy to remove
Malignant Tumors • May lose cellular ID and attachment need • Metastasis: This is when the cancer cells spread to other parts of the body
Cancer Cells Lack Density- Dependent Inhibition Normal cells given nutrients, growth factors and substrate only form a layer one cell deep. Cancer cells lack this inhibition.
Cancer: Caused by Mutations • Tumors are the result of mutations. • Mutated cells show several common errors: • Cells lack density-dependent inhibition • Cells lack anchorage dependence. • Cells become immortal • Growth factors can promote tumor growth