Cell Reproduction and DNA

History of Cells

• During the 17th century, the invention of the microscope helped scientists examine drops of blood, scrapings from their teeth, and other small things.

• In 1665, Robert Hooke cut a thin slice of cork and looked at it under his microscope…he saw squares and named those squares cells.

• In the 1830’s, plants were examined an were determined to be made of cells also.

http://www.youtube.com/watch?v=4OpBylwH9DU

The Cell Theory

Rudolph Virchow hypothesized that:

• All organisms are made up of one or more cells

• The cell is the basic unit of organization in organisms

• All cells come from cells

Cell Review

• There are two types of cells:• Prokaryotic cells don’t

have a nucleus.• Ex: bacteria

• Eukaryotic cells have a nucleus

• Ex. Plants and animal cells

Cell Structures• Cell walls: outer coverings

that protect cells and give them shape.

• Cytoplasm: gel like substance that contains the cytoskeleton…gives and maintains shape of the cell

• Organelles: the structures inside of the cell

Cell Structures

• Nucleus: directs all cell activities…contains DNA (information that contains the code of all cell’s structure and activities).

• Mitochondria: a structure where energy is released from the breakdown of food into CO2 and water.

• Ribosomes: a structure that makes proteins needed for chemical reactions

Cell Division and Mitosis

• Cell division — increases the number of cells and causes many-celled organisms to grow

• The Cell Cycle — series of events that takes place from one cell division to the next

• Cells have periods of formation, growth and development, and death called life cycles.

• http://www.youtube.com/watch?v=L0k-enzoeOM

Cell Division and Mitosis• Chromosome—structure in the

nucleus that contains hereditary material

• Interphase — most of the life of any eukaryotic cell, or cell with a nucleus, is spent in a period of growth and development.

• During interphase, a cell duplicates its chromosomes and prepares for cell division.

• After interphase, the nucleus divides, and then the cytoplasm separates to form two new cells.

• Mitosis - process in which the nucleus divides to form two identical nuclei

Prophase

• Nucleolus and nuclear membrane disintegrate. • Centrioles move to opposite ends of the cell. • Spindle fibers begin to stretch across the cell.

Metaphase• Pairs of chromatids line up across the center of the cell.

Anaphase• Each centromere divides. • Each pair of chromatids separates and moves to

opposite ends of the cell.

Telophase

• spindle fibers disappear and a new nucleus forms.

Animal vs. Plant Cells• Cytokinesis: Division of the Cytoplasm—for most cells, the cytoplasm separates after the nucleus divides

In animal cells, the cell membrane pinches in the middle and the cytoplasm divides.

In plant cells, a cell plate forms.

Extra Large, Semi-3D Mitosis Thingy

• Divide into groups of 3-4.• Using a large piece of paper, divide up the steps

of Mitosis, including Interphase, and make a large diagram.

• All of the essential cell structures must be labeled in each step.

• Describe what happens in each step.• Pick one cell structure in each step and make it

3D…a different structure must be 3D in each step.

Cell and Mitosis Quiz

1. Explain one of the main ideas of the Cell Theory.

2. What is the function of the nucleus in the cell?

3. In your own words, explain the purpose of mitosis.

Results of Mitosis• Each cell in your body, except sex cells, has a nucleus with 46 chromosomes.• Allows growth and replaces worn out or damaged cells

Asexual reproduction — a new organism is produced from one parent organism.

An organism with no nucleus divides (bacteria) into two identical organisms by fission.

Budding — a small, exact copy of the adult grows from the body of the parent.

In regeneration, a whole new organism grows from each piece of the parent.

Section 2: Sexual Reproduction and Meiosis

Sexual reproduction—two sex cells, usually an egg and a sperm, come together.

Fertilization—the joining of an egg and a sperm, generally from two different organisms of the same species

– Sperm are formed in the male reproductive organs.

– Eggs are formed in the female reproductive organs.

– A cell that forms from fertilization is a zygote.

Following fertilization, cell division begins and a new organism develops.

Sexual Reproduction

Human body cells are diploid, because they have 23 pairs of similar chromosomes = 46 total chromosomes.

Human sex cells are haploid, because they have 23 single chromosomes

In Meiosis I, each chromosome is duplicated, just as in mitosis. The steps of Meiosis I are identical to mitosis…

http://www.youtube.com/watch?v=qCLmR9-YY7o&feature=fvsr

In meiosis II, the nuclei divide and the chromatids separate, producing four cells with half the number of chromosomes of the

original nucleus.

Prophase II: Duplicated chromosomes and spindle fibers reappear in each new cell.Metaphase II: Duplicated chromosomes move to the center of the cell. Each centromere now attaches to two spindle fibers instead of one.Anaphase II: The centromere divides and the chromatids separate and move to opposite ends of the cell. Each chromatid is now an individual chromosome.Telophase II: Spindle fibers disappear, nuclear membrane forms around each set of chromosomes, cytoplasm divides

Mitosis/Meiosis Venn Diagram

• You must have at least 4 points in each section (12 total)

• You must include 4 pictures in each section…• They can correspond with your 4 points or

can be separate.

Chapter 4Section 3

DNA – Deoxyribonucleic Acid:– a chemical that contains information that an organism

needs to grow and function

– Watson and Crick described first accurate model of DNA in 1953.

• They were awarded the Nobel Prize for physiology in 1962

• Some scientists believe the discovery of DNA was the most important biological event of the century

• Why? – Led to improved plants and animals, and to help in detecting and preventing inherited disorders

http://www.youtube.com/watch?v=hnSPGlpZx_Q

The structure of DNA is similar to a twisted ladder.

• The sides of the ladder are made up of sugar-phosphate molecules.

• The rungs of the ladder are made up of nitrogen bases.

• The 4 nitrogen bases are Adenine, Thymine, Guanine and Cytosine.

• Adenine always pairs with Thymine

• Guanine always pairs with Cytosine

• Before a cell divides, its DNA duplicates itself by unwinding and separating its sides.

• Each side becomes a pattern on which a new side forms.

• Genes – sections of DNA on a chromosome

• Unit of heredity• Contain

instructions for making specific proteins

DNA Double Helix Replica

Day One/Two

1.Take 2 “backbone” sheets, and 1 of each of the colored sheets of base pairs.

2.Cut out one sheet of “backbone” pieces and half of each of the base pairs.

3.Using your DNA blueprint, assemble your DNA double helix (Only bolded base pairs today).

4.Make sure you pair the correct base pairs together!

• RNA carries the codes for making proteins from the nucleus to the ribosomes in the cytoplasm.

• Messenger RNA carries the code that directs the order in which the amino acids bond.

• Ribosomal RNA makes up ribosomes, where proteins are built.

• Transfer RNA brings amino acids to the ribosomes to build the protein.

• RNA has nitrogen bases like DNA but contains Uracil instead of Thymine. So..

• Adenine pairs with Uracil

•Guanine pairs with Cytosine

• Mutations - any permanent change in the DNA sequence of a cell's gene or chromosome

– Can be caused by outside factors like X rays, sunlight, and some chemicals

– A change in a gene or chromosome can change the traits of an organism.