Roche A. Samy
Objectives
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After completing this lesson, students should be able to:
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1. Explain that the factors studied by mendel are now called genes, located in chromosomes in the nuclei of cells.
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2. Explain with the aid of diagrams that the chromosomes are made up of long coiled, chemical chains known as DNA.
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3. Demonstrate and describe the fact that during meiosis and mitosis, DNA is duplicated to make it possible for chromosomes and their genes to be passed on to new body cells and reproductive cells.
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4. Define and explain with examples the terms genotype and phenotype, homozygous and heterozygous and variations in inheritance.
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5. Explain the sex chromosomes (xx for females and xy for males) that determine the sex of the offspring.
Activity
: (Supplement with AV-2)
Modeling Chromosomes
For many of the average students, modeling of chromosomes is necessary to understand the difference between mitosis and meiosis because they lack the facility to understand abstract concepts. Hence, they will find the models very helpful.
Each student is given some clay of various colors, with enough of each color to make pairs of “chromosomes”. The students can then draw circles on sheet of paper, to represent stages of the cells. The students then place the right number and kind of chromosomes in each kind of cell as it undergoes mitosis and as it undergoes tow divisions in meiosis. It is hoped that this will help clarify the difference between the two processes. This activity can be combined with exhibition of movies or video tapes describing DNA.
Check Up Question
:
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1. In what part of a cell are DNA, chromosomes and genes found?
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2. List the parts of the DNA and describe how they are arranged.
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3. Explain in your own words why DNA replication is necessary for meiosis and mitosis to occur.
