Chapter 9 Cell Reproduction Review What we know

Chapter 9 Cell Reproduction

Review: What we know • Cells have DNA / genetic information • We pass on our info to our children • All our cells contain DNA • Chromosomes are bundles of DNA

What we need know • How do our cells make new cells? • What can go wrong? • Do all cells get made the same? • Can do bacteria and viruses make new cells?

In the beginning… • You start life as a single cell Human Embryo Day 3 Human Embryo 20 Weeks

Until the end of time… • New cells made throughout entire life • Called cell reproduction

Cell Reproduction • Goal: – Replace old or worn out cells – Growth & Development • Processes: Interphase, Mitosis & Cytokinesis

Mitosis • Result = two identical cells • Forms all human body cells • Ex: skin, blood, bones, stomach • Slows with age

Cell Cycle AKA A Cell’s Life

Before Cells Divide • DNA replication occurs chromosomes double • This stage of the cell cycle is called interphase

Interphase • Longest stage of cell cycle • Cell is preparing for mitosis • Cell gets larger & centrioles double

Interphase

Interphase (cont. )

Plant Cells in Interphase

Plant Cell in Interphase (cont. )

Stages of Mitosis P–M–A–T

PROPHASE • Chromosomes shorten & thicken • Nuclear membrane breaks down • Centrioles move apart • Spindle fibers form between centrioles

Prophase

Plant Cell in Early Prophase

Plant Cell in Late Prophase

METAPHASE • Centrioles move to opposite sides of cell • Spindle fibers stretch between centrioles • Chromosomes line up on fibers at centromere

METAPHASE (cont. ) • Chromatids are pulled to line up at center of cell • “Meta-” Prefix meaning middle

Centromere • Part that holds chromosomes together

Plant Cell in Metaphase

Plant Cell in Metaphase

ANAPHASE • Sister chromatids are pulled apart • Fibers pull chromatids toward centrioles

Anaphase

Plant Cell in Anaphase

Plant Cell in Anaphase

TELOPHASE • Fibers begin to disappear • Nuclear membrane begins to reform • Cell membrane pinches in

Plant Cell in Telophase

Cytokinesis • Process of dividing the cytoplasm • Starts during anaphase finishes after telophase

In the end… • Each cell has a complete set of chromosomes • Two identical daughter cells formed from one parent cell

Mitosis Completed

http: //www. edumedia-sciences. com/en/a 70 -mitosis

Changes in Rate of Mitosis • Cancer: Cells divide at a fast rate out of control • Malignant: dangerous • Benign: not dangerous

Abnormal Cell Division • A tumor is a mass of tissue that results from excessive cell division

How other cells divide 1. Bacteria (Prokaryote) One cell splits into two § Asexual reproduction § Same genes as “parent”

Bacteria Cell Reproduction

How other cells divide (cont. ) 2. Viruses – Inject their DNA into other cells § Not considered “living” cells

Viral Cell Reproduction Step 1 Step 3 Step 2 Step 4