CELLS Growth and Reproduction

Mitosis

I. Structure & FunctionCells that make up an organism

come in a lot of sizes and shapes. Remember: Structure relates to functionJournal: What does this mean?

II. Size limitations & Surface Area to Volume Ratio

• Surface Area to volume Ratio– As a cell grows, its surface area becomes smaller

than its volume…..

The Importance of High Surface Area to Volume Ratio

• Diffusion of necessary nutrients into the cell • DNA RNA Proteins

III. Characterizing Cells based on chromosome number

• Diploid Cells: Cells having two sets of chromosomes– Normal cells of the body are diploid– Commonly abbreviated 2n

• Haploid Cells: Cells that contain only one set of chromosomes– Typically reproductive cells, called gametes– Commonly abbreviated 1n

Which process produces diploid cells? Haploid cells?

DNA• Chromatin: DNA that is not coiled• Chromosomes: Chromatin (DNA) and proteins

that are rod shaped. – Ready for cell division

• Histones: proteins that help maintain the shape of chromosomes and aid in the tight packing of DNA

Chromosome structure• Sister chromatids: two identical halves of a

chromosome• Centromere: middle of a chromosome that

holds the two chromatids together until they separate during cell division.

a. Why are sister chromatids important?

Sister Chromatids are duplicates of a genome. When the cell divides, each cell receives a complete copy off all of the DNA

Sister chromatids

DNA Doubles – forming attached sister chromatids (look like an X)

Chromosome Numbers• Each species has a characteristic number of

chromosomes.

• Journal: Using evidence from the table above, does chromosome number relate to organism complexity?

b. What are the 2 types of chromosomes found in an animal cell?

• Sex Chromosomes: determine the gender of an organism– Male XY– Female XX

• Autosomes: the remaining chromosomes beyond the sex chromosomes

• Homologous Chromosomes: Two copies of each autosome

c. Where did each copy of the homologous Chromosomes found in your cells come from?– One from each parent– Same size and shape– Carry genes for the same trait

• Also called Homologues

d. What is a Karyotype? • Photomicrograph of all of the chromosomes in

a dividing cell

THE CELL CYCLE• Sequence of growth and division in a cell

In Prokaryotes: Binary Fission

The Cell Cycle In Eukaryotes:• Sequence of growth and division in a cell

2 Parts:– Interphase:G1: Growth 1 – prep for DNA replicationS: Synthesis – DNA replicationG2: Growth 2- prep for cell division– Mitosis:

The Cell Cycle In Eukaryotes:• Sequence of growth and division in a cell

2 Parts:– Interphase: Cell grows, makes proteins, and

DNA is replicated in preparation for mitosis– Mitosis: The process of nuclear division that

results in two daughter cells• Occurs in unicellular organisms like amoeba • It occurs in the addition of cells to a tissue or an

organ in multicellular organisms

Mitosis: 4 phases

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

1. Prophase

• Chromatin coils up into visible chromosomes• Nuclear envelope disappears• Centrioles migrate to opposite sides of the cell• Spindle fibers form

2. Metaphase

• Chromosomes become attached to spindle fibers and begin to line up in the middle

3. Anaphase

• The sister chromatids are separated and pulled apart to opposite ends of the cell

4. Telophase

• The sister chromatids are at opposite ends of the cell.

• The nuclear envelope reappears

Cytokinesis: • The division of the cell’s cytoplasm.

• How is cytokinesis different between plants and animals?– In animal cells, the plasma membrane pinches in

along the equator (forms a cleavage furrow)– In plant cells, a rigid cell wall is laid down along

the equator (forms the cell plate)

Animal Cells Plant Cells

• What are the levels of organization?

Cell Tissue Organ Organ System Organism

Mitosis allows for new cells to be produced. These cells will be differentiated, or specialized, during development.

Remember, the basic unit of organization is still the CELL!!!

THE END