The Cell Cycle

Limits to Cell Growth Living things grow by producing MORE cells Your body is constantly making new cells The life cycle of a cell is called the cell cycle

Limits to Cell Growth 2 main reasons that cells divide rather than continuing to grow indefinitely: The larger the cell, the more demands it places on its DNA The larger, the more problematic transport becomes into/out of the cell

The Cell Cycle Begins: when the cell is formed Ends: once the cell has divided and has formed new cells

The Cell Cycle

The Cell Cycle DNA organized into chromosomes (found in the nucleus)

The Cell Cycle DNA organized into chromosomes (found in the nucleus) During the cell cycle the cell must copy DNA (found in chromosomes) to pass onto the newly formed cell

The Cell Cycle Prokaryotic cells: Bacteria Binary fission “splitting into 2 parts”

The Cell Cycle Binary Fission

The Cell Cycle Eukaryotic cells: Chromosomes contain more DNA than in prokaryotic cells

The Cell Cycle Eukaryotic cells: All body cells in organism have same number of chromosomes and exactly the same DNA Humans have 46 chromosomes!

The Cell Cycle Eukaryotic cells: most organisms have chromosomes in matching pairs - one from each parent- called homologous chromosomes Humans have 23 pairs !

Homologous Chromosomes

The Cell Cycle Three Stages interphase: cell grows and copies organelles & chromosomes -longest phase of cycle -divided into 3 stages

The Cell Cycle Three Stages Interphase: G1 - growing; increase in size; make new organelles & proteins S - replication of chromosomes G2 - cell division molecules produced

The Cell Cycle Interphase: In a cell that is not dividing, the DNA is in the nucleus and is in long, tangled strands called chromatin When a cell gets ready for division (mitosis), DNA must get organized!

The Cell Cycle Interphase: Think of DNA like thread. As chromatin the thread is all tangled. As a chromosome, the DNA is all wound up and organized, like thread on a spool.

Structure of a Chromosome Each side of 'X' is a chromatid Each chromatid is identical in the information it contains - replicated DNA

Structure of a Chromosome The center structure that holds 2 sister chromatids together is called a centromere

Structure of a Chromosome

The Cell Cycle Three Stages 2. Mitosis: chromatids separate and 1 cell divides into 2 Each cell has a nucleus with the same number of chromosomes Divided into 4 stages

Mitosis (cell division) Prophase Metaphase Anaphase Telophase

The Cell Cycle Mitosis Prophase Nuclear membrane dissolves Chromatin condense into chromosomes Centrioles separate (opposite poles) and form spindle fibers

The Cell Cycle Mitosis prophase

The Cell Cycle Mitosis prophase

The Cell Cycle Mitosis Metaphase Homologous chromosomes pair up at the equator Connected to spindle fibers at centromere

The Cell Cycle Mitosis metaphase

The Cell Cycle Mitosis metaphase

The Cell Cycle Mitosis Anaphase Sister chromatids separate into individual chromosomes and move to opposite poles of cell

The Cell Cycle Mitosis anaphase

The Cell Cycle Mitosis anaphase

The Cell Cycle Mitosis Telophase Nuclear membrane forms around each set of chromosomes & they unwind

The Cell Cycle Mitosis telophase

The Cell Cycle Mitosis telophase

Can you identify the stages?

The Cell Cycle Three Stages 3. Cytokinesis: the division of the cytoplasm two new cells (daughter cells) each identical

The Cell Cycle Cytokinesis: -animal cells: pinched -plant cells: form a cell plate