PRACTICAL ACTIVITIES TO DEMONSTRATE CONTINUOUS VARIATIONS
Height of students
- Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall.
- Or door as one student stands straight without shoes, next to the wall or door.
- The height for each student is recorded on chalk board.
- The frequency distribution of height is recording as the height is grouped into various classes.
- A histogram to represent frequency against height is drawn.
- The normal bell shaped curve is observed.
Discontinuous variations – ability to roll tongue
- The number of students who can roll their tongue is recorded as well as the number of non-tongue rollers.
- The ratio of tongue-rollers to non-tongue rollers is worked out.
- Gene for the ability to roll the tongue is dominant, therefore is expected more tongue rollers.
Demonstration of Mitosis and Meisosis
- Plasticene is used to represent number and shapes of various chromosomes e.g. 8 in Drosophila melanogaster.
- Each stage of mitosis illustrated e.g. interphase.
- Each is rolled to appear long is and coiled, prophase is each made into a ball and then shaped to the appropriate length; and split into two to represent chromatids.
- Centromeres for different chromosomes can be illustrated in different positions.
- Each stage of mitosis is illustrated and telophase can be illustrated by surrounding the “chromosomes” with a long many drawn plasticene to represent cell membrane.
- It is manipulated to show how telophase takes place.
- The same procedure is followed.
- Plasticine with contrasting colours is used to show clearly gene mixing in crossing over.
- Each pair of homologous chromosomes is represented by plasticene with two different colours e.g. red (paternal) blue for maternal chromosome.
- All the steps in the two stages of meiosis are illustrated up to the production of four haploid gametes.
Human Finger Prints
- The finger prints for each student’s thumb, forefinger and middle fingers of the left hand are imprinted on a white paper.
- A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad.
- For best results students work in pairs.
- Observations are made at all forefingers, thumb prints and differences noted.
- The main patterns are noted. It is also noted that no two, fingerprints are exactly similar.
PRACTICAL APPLICATIONS OF GENETICS
COMPLETE AND INCOMPLETE DOMINANCE