Category: Cellular Processes

Introduction:        Living things have bodies that are adapted for the places they live and the things they do. Fish have gills so that they can remove oxygen that is dissolved in water. Most plants have green leaves which contain chlorophyll so that they can make food. Jellyfish have stinging cells to capture prey. Birds have hollow spongy bones so that they will be light enough to fly. Arctic animals have layers of fat and thick coats of fur to keep warm in the frigid Arctic climate. There are hundreds of examples of ways that organisms are adapted for a successful lifestyle.       Humans, too, are adapted for the things they do. One of our adaptations is our hand. Humans, as well as monkeys, gorillas, and other primates, have a hand that can grasp objects. We are able to grasp objects because of our opposable thumb. When students first hear or read about the opposable thumb during discussions of human evolution, they may perceive it as an anatomical fact with little seeming importance. In this activity, students will discover which of their simplest daily activities are possible only because of their opposable thumbs, which activities take longer without the use of an opposable thumb, and what sort of human activities would not be likely in the absence of an opposable thumb.   In this lab exercise, you will perform several common actions. Then you will change your hand so that it resembles that of a non-primate animal. You will determine whether or not you can successfully perform the same actions. This will demonstrate how the human hand is adapted for the actions it performs. You will work with a partner to do this exercise.   Materials: (per group)

• masking tape
• scissors
• paper clips
• zip-lock storage bag
• plastic fork and knife
• small amounts of food items to be cut
• pencil
• jar with screw-on lid
• paper
• roll of tape
• balloons
• comb
• book
• lace-up shoe
• clock with a second hand
• Piece of yarn or string
• balloon
• clothes with zippers & buttons

Procedure: Using masking tape, have your partner tightly tape each of your thumbs to the palm of the hand. Then, try to complete the tasks that are listed below. Be careful not to use your thumbs. Have your partner record on your data table how long it takes to do each task with your thumb taped and then with your thumb free. If an activity takes longer than 2 minutes, record the event as unsuccessful . After completing each item, write out the answers to the following questions:

• Is the task more difficult with or without an opposable thumb?
• How did you have to change your usual technique in order to complete this task?
• Do you think organisms without opposable thumbs would carry out this task on a regular basis? Why or why not?

Tasks:

1. Pick up a single piece of paper. Put it down on your desk.
2. Pick up a pen or pencil from the table top. Use it to write your name on the piece of paper.
3. Open a book. Turn single pages in the book.
4. Unscrew a bottle cap or jar cover.
5. Use a fork and knife to cut a food item into small pieces.
6. Tear off a small piece of tape.
7. Turn on the water faucet. (Complete activity #8!) Turn it off.
8. Moisten a paper towel and wash and dry the desktop.
9. Sharpen a pencil.
10. Cut a circle out of a piece of paper using scissors.
11. Pick up all the scraps from activity #10 and throw them into the recycling box.
12. Comb your hair.
13. Open a door.
14. Pick up one paper clip. Clip a pile of papers together.
15. Tie your shoelaces.
16. Button several buttons.
17. Zip up your jacket.
18. Blow up a balloon and tie it.
19. Tie a knot in a piece of string.
20. Close a zip-lock bag.

Data:

Conclusion:   1. Explain why dog and cat paws are not adapted for doing the six actions you tested.     2. What are cat and dog paws adapted for?     3. Describe how your hand is adapted for doing the actions you tested.       4. You have an opposable thumb. Explain what this means.     5. Why do you feel that human hand adaptations have helped to make humans such a successful species on earth?

Chromatography of Inks

Introduction:

One of the main jobs of biochemists is to unravel the complexities of chemical compounds and reduce them to their individual components.  The term chromatography comes from two Greek words, “chromat” meaning color and the word “graphon” meaning to write.  Separation of the components of chemical compounds can be done by using several methods. Liquids can be separate by High Performance liquid Chromatography (HPLC), while the components of gases are separated by Gas Chromatography.  Chromatography is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.

Chromatography was first used to separate pigments (colors) in leaves, berries, and natural dyes. Paper chromatography is a technique used to separate, isolate, and identify chemical components of a compound. In paper chromatography, the solid surface is the cellulose fibers in the chromatography paper.  A solvent or developer (water, alcohol, or acetone) is placed in the bottom of the chromatography chamber. The paper acts as a wick to pull the solvent up the paper. The solvent front will “wick” up the chromatography paper by capillary action.  A minute drop of the ink or chemical mixture to be separated is placed near the bottom of the strip of chromatography paper, but slightly above the level of the solvent in the chamber.  As the solvent passes over the drop of ink, the components of the ink dissolve in the solvent. Because the components of the ink do not all dissolve at the same rate, as the components of the mixture move upward, they show up as colored streaks.  The separated substances on the chromatography paper form a color pattern called a chromatogram.

To determine the rate of migration for each pigment or component of the ink, the Rf value for each pigment must be calculated. The Rf value represents the ratio of the distance a pigment moved on the chromatogram relative to the  distance the solvent front moved. Each pigment or compound will have a unique Rf value that scientists can use to identify the substance. The Rf value is calculated using the following formula:

Rf = distance traveled by the compound / distance traveled by the solvent

Objective:

Use the process of paper chromatography to separate the pigments in various markers and then determine the Rf value for each color on your chromatogram.

Materials:

Plastic vials, paper clips, markers in assorted colors, chromatography paper, scissors, pencil

Procedure:

1. Obtain chromatography vials and chromatography strips, and different color markers so that each person in the group will have two chromatograms.
2. Cut one end of the chromatography strip to a point. The bottom of the point will mark the starting point for movement of the solvent (H2O).
3. About 2.0 centimeters from the bottom of the strip, draw a faint horizontal line with pencil. This will mark the starting point for measuring the migration distance of each color.
4. Using a different color marker for each strip, drop a dot of ink on the center of the horizontal pencil line.  Let this dry a moment & then add more ink to the dot.
5. Add a small amount of water to the bottom of the chromatography chamber. (The ink dot should be ABOVE the surface of the water.)
6. Straighten a paper clip and poke a hole through the top of your chromatography strip
7. Use the paper clip to hang the strip in your chamber. (The straighten paper clip will lay across the top of the chamber.)
8. MAKE SURE THE TIP OF THE STRIP BUT NOT THE INK IS IMMERSED IN THE WATER!
9. Notice the separation of the ink as both the solvent and ink travel up the chromatography strip.
10. Once the solvent front has neared the top of the strip, remove the strip from the chamber and lay it on a piece of paper towel.
11. Immediately mark the solvent front with a faint pencil line.
12. Immediately mark the leading edge of each color with an “x”.
13. Measure, in millimeters, the distance the solvent migrated from the tip of the strip to your solvent front pencil line.
14. Measure, in millimeters, the distance each color migrated from the point of origin (pencil line where the ink dot was placed) to the leading edge of the color (marked with an “x”.
15. Record all data in Data table 1.
16. Calculate and record the Rf value for each color using the formula below.

Rf = distance traveled by the compound / distance traveled by the solvent

Data Table 1

Questions:

1. Which color of marker did you use?

2. which color separated out first from your ink dot?

3. Why did the inks separate?

4. What was your solvent?

5. If you had used markers that weren’t water-soluble, how would you have had to change this lab?

6. Why did some inks move a greater distance than others?

7. How do scientists use paper chromatography in their investigations?

Introduction:

Have you ever noticed that brothers or sisters often look alike?  Their inherited traits are what make their physical appearance so similar. An inherited trait is a particular genetically determined characteristic that distinguishes a person. The traits of children are determined by the traits that  are passed on from their parents. Some traits are obvious in a family — a child’s nose is shaped like their mother’s nose, but some traits are less obvious. You may have similar traits to many of your classmates even though you are not related to them. Some examples of often un-noticed human traits are the ability or not to roll your tongue, attached or unattached earlobes, dimples or freckles, naturally curly or straight hair, hitchhiker’s or straight thumb, straight or widow’s peak hairline, smooth or cleft chin, or colorblindness or normal vision.

There are numerous traits in humans, but some traits occur more frequently than others.  Between 70-90% of the human population have free-hanging earlobes, can roll their tongue,  are right-handed, and can taste a chemical called PTC.  These traits are called high frequency traits.

Objective:

Students will determine the presence of certain high frequency traits in themselves & their classmates.

Materials:

Genetic Inventory sheet with pictures, paper, pencil, PTC taste strips.

Procedure:

1. Identify which of the following 10 human traits you have by placing a check mark beside that trait.
2. Compare the traits you have with other students in the classroom and find the student you most closely match.

 

Tongue Roller	Non Roller	Dimples	No Dimples
Attached Earlobes	Unattached Earlobes	Widow’s Peak	Straight Hairline
Longer Second Toe	Short Second Toe	Bent Little finger	Hitchhiker’s Thumb
Attached Ear lobes (left) Unattached ear Lobes (right)	“VULCAN” or No “VULCAN”	Dimples	Right/Left Thumb on top

 

 Fundamentals of Genetics

Section 9-1 Mendel’s Legacy

1. What scientist is responsible for our study of heredity?

2. Define heredity.

3. What plant did Mendel use for his hereditary experiments?

4. Name the 7 characteristics, giving both dominant and recessive forms of the pea plants, in Mendel’s experiments.

5. In order to study pea plant traits, Mendel had to control __________________ among the plants.

6. Define pollination & name 2 types.

7. How do pea plants normally pollinate?

8. How can cross-pollination of pea plants be done?

9. How did Mendel obtain pure pea plants?

10. What is the P1 generation? How is it obtained?

11. What is the F1 generation &how is it obtained?

12. How did Mendel obtain his F2 generation?

13. When Mendel crossed his P1 plants to get the F1 generation, what ratio did he get?

14. What is the difference between dominant & recessive genes?

15. State Mendel’s law of segregation.

16. What are alleles?

Section 9-2 Genetic Crosses

17 What is the difference between genotypes & phenotypes?

18. Write the 2 genotypes for a purple flower.

19. Write the genotype for a white flower.

20. What is the difference in a homozygous and a heterozygous genotype?

21. What is  probability & tell 3 ways they can be expressed.

22. What is the probability that you will get “heads” each time you flip a coin?

23. What is a monohybrid cross?

24. Give an example of a monohybrid cross.

25. What is a Punnett Square used for?

26. Sketch the Punnett Square for crossing a pure purple flower with a white flower.

27. Use a Punnett Square to solve this cross — PP x pp.

28. What percentage of the offspring from this cross are purple? White?

29. Use a Punnett Square to solve this cross in guinea pigs — BB x Bb. Hint: See page 174.

30. In the above cross, what coat colors & percents did you get?

31. What phenotype (coat color) would each of these guinea pig genotypes result in:

        a. Bb?

        b. BB?

        c. bb?

32. Use a Punnett Square to solve this cross for coat color in rabbits: Bb x Bb?

33. What percent of the rabbits will have black fur? Brown fur? What ratio does this give for coat color?

34. Define genotypic ratio.

35. What is the genotypic ratio for all F1 crosses (bb x Bb)?

36. Define phenotypic ratio.

37. What is the phenotypic ratio for all F1 crosses?

38. What is a testcross?

39. A testcross can determine which individual’s phenotype is ________________________.

40. Use a Punnett Square to solve the following 2 testcrosses:

        a. BB x Bb

        b. bb x Bb

41. In each of the above testcrosses, tell how many offspring have black coats (dominant) and how many will have brown (recessive) coats?

42. What does complete dominance mean?

43. Give an example of complete dominance in pea plants.

44. What is incomplete dominance?

45. How many alleles influence the phenotype in:

        a. complete dominance?

        b. incomplete dominance?

46. Using four-o-clocks, give an example of how incomplete dominance occurs. Be sure to tell all possible genotypes & phenotypes.

47. Give the following ratios for crossing 2 pink four-o-clocks (Rr x Rr):

        a. Genotypic ratio?

        b. Phenotypic ratio?

48. Define codominance.

49. In what genotype does codominance appear?

50. In horses, _________________ coat color is a result of codominance.

51. Write the genotype for roan coat color & tell the color of each allele in the genotype.

52. What is a dihybrid cross?

53. How many different genotypes will result in a dihybrid cross when 2 homozygous organisms are crossed?

54. The offspring from a dihybrid cross of 2 homozygous organisms will all be __________________________.

55. Use a Punnett Square to show the results of the following cross: RrYy x RrYy

56. How many different genotypes resulted from this cross?

57. How many different phenotypes resulted from this cross?

58. Write the genotypes for each of these phenotypes:

        a. Round, green seeds

        b. Wrinkled, yellow seeds

        c. Wrinkled, green seeds