Cell Division

Mitosis is a cell division process that produces two daughter cells that are identical in chromosome number and in chromosome combination. For example, if a cell has 4 chromosomes and divides by mitosis, it will produce two daughter cells each having 4 chromosomes. This type of cell division is used as a form of reproduction for single cell organisms. However,most multicellular organisms use this type of cell division for growth, repair and to replace cells that have died. To further enhance your understanding of this cellular process, click on the following link. MITOSIS ANIMATION Note: Cancer is uncontrollable mitosis.

Meiosis is a cell division process that produces 4 daughter cells that are not identical. Meiosis is the cell division that produces the gametes or sex cells. The sperm is the male sex cell and the egg is the female sex cell. Cells that are produced by meiosis are not identical in chromosomes combination and have half the number of chromosomes as the parent cell. For example, humans have 46 chromosomes; our sex cells, each have 23 chromosomes. Fertilization or the union of the sperm and the egg restores the number of chromosomes to 46. For further elaboration of this process, clink on the following link.

MEIOSIS ANIMATION

MEIOSIS ANIMATION2

Mitosis vs Meiosis

Karyotype

Karyotype is a technique used to detect chromosomal abnormalities. To carry out this process, the cell cycle is arrested or stopped during mitosis when the chromosomes are coiled and visible. Karyotyping separates and aligns chromosomes by matching pairs. This facilitates the identification of any inconsistency. Diseases like Down Syndrome and other chromosomal diseases can be detected using this procedure. To learn more, click on the following links.

Click Karyotype Activity

List two diseases that can be diagnosed using this procedure. (Hint: look up chromosomal diseases)

Evolution

Evolution is the theory that stipulates that life began as a single cell. Over time, with the struggle to survive the environment, organisms changed to the multitude of life forms that exist today. The mechanisms responsible for driving the evolutionary process are mutations, which are permanent changes in the organism's genetic code and sexual reproduction. One important thing to remember, in order for the organism to evolve, it must first survive or be selected. It must have some favorable traits that allow it to survive changes in its surrounding. To learn more about the theory of evolution, go to the following links.

EVOLUTION

EVOLUTION2

ADAPTATION

Quiz

• What are the mechanisms that drive the evolutionary process?
  
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• How does adaptation leads to evolution?
  
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• What happens when an organism fails to adapt?
  
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• Explain Darwin's proposed explanation for Natural Selection.
  

Competition and Natural Selection

In nature, organisms tend to overproduce. In a given population, there is always variations among individuals. During competition, organisms that have favorable traits for this task will survive and are said to be selected. These organisms will reproduce and pass on those traits to their offspring. Thus, the frequency of organisms with those traits will increase. Note: only the offspring or organisms that survive will eventually evolve. To learn more, go to the following link.

COMPETITION AND NATURAL SELECTION

NATURAL SELECTION

Darwin's Proposed Explanation of Natural Selection

• In Nature, organisms produce more offspring than can survive.
• In any population, individuals have variations.
• Individuals with favorable variations survive, reproduce and pass on those traits
• Overtime, offspring with certain variations make up most of the population and may look entirely different from their ancestors.

To check your understanding of Darwin's explanation, go to this link and problem #12

Darwin's Theory

HEREDITY

Heredity is the passing of traits ( genes) from parents to offspring. For example, your eye color, your hair texture and your height are traits or characteristics that you inherit or receive from your mom and your dad. To read more, click this link. HEREDITY

To further your understanding on how traits are inherited, click this link.
MENDELIAN GENETICS

Build a DNA molecule or DNA replication

DNA is copied or replicated during preparation for cell division, either mitosis or meiosis. The bases are paired as follows: adenine with thymine, cytosine with guanine. To build a model of the DNA, click this link: Build a DNA Molecule

Click on DNA replication

THINK:

Any error that occurs during DNA replication is called __________ ?

Why must the DNA replicate?

Where do you find DNA inside the cell?

Click this link and answer question # 10 Problem # 10

DNA Structure

The DNA is the master molecule that contains all of your heredity information. This molecule has a helical shape. It is shaped like a twisted ladder. For further enlightment, click the following link. DNA STRUCTURE

Quiz

1. What are the subunits of DNA?
2. List the parts of the nucleotides.
3. Identify the sugar found on DNA.
4. What is the difference between a gene and a chromosome?
5. Identify the two types of cell division.
6. How are cells produced by mitosis different from cells produced by meiosis?
7. What is the advantage of sexual reproduction?
8. A ____________ is any permanent change on the DNA.
9. How do the bases pair during replication?