My Classroom Material 100 - BIOLOGY JUNCTION

Population Genetics and Evolution

Population Genetics and Evolution
Introduction:
In 1908, G.H.Hardy and W. Weinberg independently suggested a scheme whereby evolution could be viewed as changes in frequency of alleles in a population of organisms. In this scheme, if A and a are alleles for a particular gene locus and each diploid individual has two such loci, then p can be designated as the frequency of the A allele and q as the frequency of the a allele. For example, in a population of 100 individuals ( each with two loci ) in which 40% of the alleles are A, p would be 0.40. The rest of the alleles would be ( 60%) would be a and q would be equal to 0.60. p + q = 1 These are referred to as allele frequencies. The frequency of the possible diploid combinations of these alleles ( AA, Aa, aa ) is expressed as p2 +2pq +q2 = 1.0. Hardy and Weinberg also argued that if 5 conditions are met, the population’s alleles and genotype frequencies will remain constant from generation to generation. These conditions are as follows:

The breeding population is large. ( Reduces the problem of genetic drift.)
Mating is random. ( Individual show no preference for a particular mating type.)
There is no mutation of the alleles.
No differential migration occurs. ( No immigration or emigration.)
There is no selection. ( All genotypes have an equal chance of surviving and reproducing.)

The Hardy-Weinberg equation describes an existing situation. Of what value is such a rule? It provides a yardstick by which changes in allelic frequencies can be measured. If a population’s allelic frequencies change, it is undergoing evolution.

Estimating Allele Frequencies for a Specific Trait within a Sample Population:
Using the class as a sample population, the allele frequency of a gene controlling the ability to taste the chemical PTC (phenylthiocarbamide) could be estimated. A bitter taste reaction is evidence of the presence of a dominant allele in either a homozygous (AA) or heterozygous (Aa) condition. The inability to taste the PTC is dependent on the presence of the two recessive alleles (aa). Instead of using the PTC paper the trait for tongue rolling may be substituted. To estimate the frequency of the PTC -tasting allele in the population, one must find p. To find p, one must first determine q ( the frequency of the non tasting allele).

Procedure:
1. Using the PTC taste test paper, tear off a short strip and press it to your tongue tip. PTC tasters will sense a bitter taste.

2. A decimal number representing the frequency of tasters (p2+2pq) should be calculated by dividing the number of tasters in the class by the total number of students in the class. A decimal number representing the frequency of the non tasters (q2) can be obtained by dividing the number of non tasters by the total number of students. You should then record these numbers in Table 8.1.

3. Use the Hardy-Weinberg equation to determine the frequencies (p and q ) of the two alleles. The frequency q can be calculated by taking the square root of q2. Once q has been determined, p can be determined because 1-q=p. Record these values in Table 8.1 for the class and also calculate and record values of p and q for the North American population.

Table 8.1 Phenotypic Proportions of Tasters and Nontasters and Frequencies of the Determining Alleles

	Phenotypes				Allele Frequency Based on the H-W Equation
	Tasters (p2+2pq)		Non Tastes(q2)		p	q
Class Population	#=	%=	#=	%=
North American Population	0.55		0.45

Topics for Discussion:
1. What is the percentage of heterozygous tasters (2pq) in your class? ______________________.

2. What percentage of the North American population is heterozygous for the taster allele? _____________

Case Studies:
Case 1 ( Test of an Ideal Hardy-Weinberg Community)

The entire class will represent a breeding population, so find a large open space for its simulation. In order to ensure random mating, choose another student at random. In this simulation, we will assume that gender and genotype are irrelevant to mate selection.

The class will simulate a population of randomly mating heterozygous individuals with an initial gene frequency of 0.5 for the dominant allele A and the recessive allele a and genotype frequencies of 0.25AA, 0.50Aa, and 0.25aa. Record this on the Data page at the end of the lab. Each member of the class will receive four cards. Two cards will have A and two cards will have a. The four cars represent the products of meiosis. Each “parent” will contribute a haploid set of chromosomes to the next generation.

Procedure:
1. Turn the four cards over so the letters are not showing, shuffle them, and take the card on top to contribute to the production of the first offspring. Your partner should do the same. Put the cards together. The two cards represent the alleles of the first offspring. One of you should record the genotype of this offspring in the Case 1 section at the end of the lab. Each student pair must produce two offspring, so all four cards must be reshuffled and the process repeated to produce a second offspring.

2. The other partner should then record the genotype of the second offspring in the Case 1 section at the end of the lab. Using the genotypes produced from the matings, you and your partner will mate again using the genotypes of the two offspring. That is , student 1 assumes the genotype of the first offspring, and student 2 assumes the genotype of the second offspring.

3. Each student should obtain, if necessary, new cards representing their alleles in his or her respective gametes after the process of meiosis. For example, student 1 becomes the genotype Aa and obtains cards A,A,a,a; student 2 becomes aa and obtains cards,a,a,a,a. Each participant should randomly seek out another person with whom to mate in order to produce offspring of the next generation. You should follow the same mating procedure as for the first generation, being sure you record your new genotype after each generation in the Case 1 section. Class data should be collected after each generation for five generations. At the end of each generation, remember to record the genotype that you have assumed. Your teacher will collect class data after each generation by asking you to raise your hand to report your genotype.

Allele frequency: The allele frequencies, p and q, should be calculated for the population after five generations of simulated random mating.

Number of A alleles present at the fifth generation

Number of offspring with genotype AA _____________ X 2= _______________ A alleles

Number of offspring with genotype Aa _____________ X 1= ________________A alleles

Total = ____________ A alleles

p =	Total number of A alleles		=
	Total number of alleles in the population

In this case, the total number of alleles in the population is equal to the number of students in the class X 2.

Number of a alleles present at the fifth generation

Number of offspring with genotype aa _____________ X 2= _______________ a alleles

Number of offspring with genotype Aa _____________ X 1= ________________A alleles

Total = ____________ a alleles

q =	Total number of a alleles		=
	Total number of alleles in the population

1. What does the Hardy-Weinberg equation predict for the new p and q?.

_____________________________________________________________________

2. Do the results you obtained in this simulation agree? __________ If not, why not?

_____________________________________________________________________

3. What major assumption(s) were not strictly followed in this simulation?

_____________________________________________________________________

Case 2 ( Selection )

In this case you will modify the simulation to make it more realistic. in the natural environment , not all genotypes have the same rate of survival; that is, the environment might favor some genotypes while selecting against others. An example is the human condition sickle-celled anemia. It is a condition caused by a mutation on one allele, in which a homozygous recessive does not survive to reproduce. For this simulation you will assume that the homozygous recessive individuals never survive. Heterozygous and homozygous dominant individuals always survive.

The procedure is similar to that for Case 1. Start again with your initial genotype, and produce your “offspring” as in Case 1. This time, However, there is one important difference. Every time your offspring is aa it does not reproduce. Since we want to maintain a constant population size, the same two parents must try again until they produce two surviving offspring. You may need to get new allele cards from the pool.

Proceed through five generations, selecting against the homozygous offspring 100% of the time. Then add up the genotype frequencies that exist in the population and calculate the new p and q frequencies in the same way as it was done in Case 1.

Number of A alleles present at the fifth generation

Number of offspring with genotype AA _____________ X 2= _______________ A alleles

Number of offspring with genotype Aa _____________ X 1= ________________A alleles

Total = ____________ A alleles

p =	Total number of A alleles		=
	Total number of alleles in the population

In this case, the total number of alleles in the population is equal to the number of students in the class X 2.

Number of a alleles present at the fifth generation

Number of offspring with genotype aa _____________ X 2= _______________ a alleles

Number of offspring with genotype Aa _____________ X 1= ________________A alleles

Total = ____________ a alleles

q =	Total number of a alleles		=
	Total number of alleles in the population

1. How do the new frequencies of p and q compare to the initial frequencies in Case 1?

_____________________________________________________________________

2. How has the allelic frequency of the population changed?

_____________________________________________________________________

3. Predict what would happen to the frequencies of p and q if you simulated another 5 generations.

_____________________________________________________________________

4. In a large population, would it be possible to completely eliminate a deleterious recessive allele? Explain.

_____________________________________________________________________

Hardy-Weinberg Problems

1. In Drosophila, the allele for normal length wings is dominant over the allele for vestigial wings. In a population of 1,000 individuals, 360 show the recessive phenotype. How many individuals would you expect to be homozygous dominant and heterozygous for this trait?

2. The allele for the ability to roll one’s tongue is dominant over the allele for the lack of this ability. In a population of 500 individuals, 25% show the recessive phenotype. How many individuals would you expect to be homozygous dominant and heterozygous for this trait?

3. The allele for the hair pattern called “widow’s peak” is dominant over the allele for no “widow’s peak.” In a population of 1,000 individuals, 510 show the dominant phenotype. How many individuals would you expect of each of the possible three genotypes for this trait?

4. In a certain population, the dominant phenotype of a certain trait occurs 91 % of the time. What is the frequency of the dominant allele?

Data Page:
Case 1 ( Hardy-Weinberg Equilibrium )

Initial Class Frequencies:

AA ________ Aa________ aa_________

My initial genotype :_______________

F1 Genotype ______

F2 Genotype ______

F3 Genotype ______

F4 Genotype ______

F5 Genotype ______

Final Class Frequencies:

AA ________ Aa________ aa_________

p _________ q __________

Case 2 ( Selection )

Initial Class Frequencies:

AA ________ Aa________ aa_________

My initial genotype :_______________

F1 Genotype ______

F2 Genotype ______

F3 Genotype ______

F4 Genotype ______

F5 Genotype ______

Final Class Frequencies:

AA ________ Aa________ aa_________

p _________ q __________

Preap Cell Study Guide

Cell Structure & Function Review

1. The first Person to describe microscopic organisms and living cells was
________________________________.

2. The maximum size to which a cell may grow is limited mainly by the cell’s ___________________________ ____________________________.

3. Short, hair-like organelles that can move and may cover a unicellular organism or line the respiratory tract are called ______________________________________.

4. Some Ribosomes are free in the cytoplasm, while others line the membrane of the
_________________ __________________ __________________________.

5. Everything between the cell membrane and the nucleus, is the cell’s
____________________________________.

6. All cells, from all organisms, are surrounded by a _______________ _____________________.

7. Membranes are _______________________ and have the consistency of vegetable oil.

8. The organelle that stores DNA and synthesizes RNA _________________________.

9. The organelle that processes and packages substances produced by the cell ______________________ _________________________.

10. The ____________________________ is the control center of the cell.

11. The DNA in the form of a long strand is called ______________________________.

12. Cytoplasm consists of two main components: ____________________________ and
______________________________.

13. The cell membrane functions like a ______________________, controlling what
__________________ and _______________________ the cell.

14. A lipid is a simple form of ________________________________.

15. There are many kinds of ______________________ in cell membranes; they help to move material into and out of the cell.

16. Scientist call the modern view of the cell membrane structure the
______________________________ ____________________ _________________.

17. The nucleus is surrounded by a double layer membrane called the
__________________________ _________________________________.

18. During cell division, _________________________ strands coil and condense into thick structures called _____________________________________.

19. The nucleoli make ___________________________. Which in turn build proteins.

20. Membranes are made mostly of ___________________ and ______________________.

21. The _________________ is the smallest unit that can carry out all of the processes of life. The basic unit of life.

22. The maximum size to which a cell may grow is limited mainly by the cell’s ___________________ ____________________.

23. The discovery of cells is linked most directly the development of the __________________________.

24. Organisms whose cells never contain a membrane bound nucleus are called _____________________________________.

24. Suspended in the cell’s cytosol are tiny ___________________________________.

25. Cell membranes consist of two phospholipid layers called a ___________________.

26. The chromosomes in the nucleus contain coded _____________________ that control all cellular activity.

27. When a cell prepares to reproduce the _______________________ disappears.

28. Cytosol is a jelylike mixture that consists mostly of _____________________.

29. The nucleus is one ______________________________.

30. In Eukaryotic cells, most organelles are surrounded by a _____________________.

31. Organisms whose cells always or usually contain a nucleus or nuclei are called
____________________________________.

32. ________________________ are structures that carry out specific functions in the cell.

33. Most cells have a single ______________________; some cells have more than one.

34. Unicellular organisms such as bacteria and their relatives are ___________________________.

35. The Fluid Mosaic Model presents the modern view of a
__________________ ___________________________.

36. The “Blueprints” in a Cell that controls all its activity are the ___________________.

37. Where are poisons and waste detoxified in a cell? _________________________ _________________________________.

38. A cell synthesizes protein by using organelles called _______________________________.

39. The Mitochondria of a cell contain an inner membrane called _____________________________.

40. What are the membrane-bound sacs that package and secrete cell products?
___________________________ ___________________________.

41. Unlike animal cells, plant cells have ______________ ________________.

42. A Chloroplast can convert _________________, __________________________, and ____________________________ into ________________________.

43. What are Flagella? ___________________________________________________.

44. In animal cells, the Cytoskeleton maintains three-dimensional structure and helps the cell ___________________________.

45. The organelle that digest molecules, old organelles, and foreign substances in the cell _______________________________________.

46. A pigment that absorbs energy in sunlight ________________________________.

47. The organelle that prepares proteins for export and synthesizes steroids is ________________________ ________________________.

48. Ribosomes differ from most organelles because they have no ___________________________.

49. What type of cells would you expect to find large numbers of mitochondria? _______________________ _________________.

50. The “Powerhouse” of the cell _______________________________.

51. Short, hairlike organelles that can move and may cover a unicellular organism or line the respiratory tract are called _______________________________.

52. The first cells on Earth were likely _______________________ that did __________ make their own _________________.

53. Microfilaments and microtubules function in cell _______________________ and ____________________________.

54. What is the correct order of structures in living things, from simplest to the most complex? ______________________, __________________________, ______________________________, ______________________________.

55. The is the organelle that transfers energy in ATP _______________________________.

56. What word means “Water Fearing”? ____________________________.

57. What word means “Water Loving”? _____________________________.

58. What is cell specialization? Give an example.
59. Distinguish between the structure of rough ER and that of smooth ER.

60. Explain how ribosomes, endoplasmic reticulum, Golgi apparatus function together in protein synthesis.

61. Explain the difference between a tissue and an organ.

62. Why is the cell membrane said to be selectively permeable?

63. If a cell has a high energy requirement, would you expect it to have many or few mitochondria? Explain your answer.

64. Describe TWO differences between prokaryotic cells and eukaryotic cells.

65. How can you determine whether a unicellular organism is a prokaryote or a eukaryote?

66. Plant cells have cell walls, but animal cells do not. Why do you think that is so?

67. What are the THREE Parts of the Cell Theory?

68. Describe three differences between plant and animal cells.

69. Name the TWO different kinds of animal cells, and describe how their shape is related to their function.

70. What is the difference between chromatin and chromosomes?

71. What are the major roles of the nucleus, and what parts of the nucleus carry out these roles?

72. What is a colonial organism, and what does it have in common with multicellular organisms?

Potato Osmosis Bi Lab

Potato Osmosis

Introduction:

A shipwrecked sailor is stranded on a small desert island with no fresh water to drink. She knows she could last without food for up to a month, but if she didn’t have water to drink she would be dead within a week. Hoping to postpone the inevitable, her thirst drove her to drink the salty seawater. She was dead in two days. Why do you think drinking seawater killed the sailor faster than not drinking any water at all? Today we explore the cause of the sailor’s death. We’ll prepare solutions of salt water to represent the sea, and we’ll cut up slices of potato to represent the sailor. Potatoes are made of cells, as is the sailor!

Objective:

The concentration of solute in a solution will affect the movement of water across potato cell membranes.

Materials:

potato, corer, 3 plastic cups, marker, salt, sugar, distilled water, paper, pencil, electronic balance, clock with second hand or timer, metric ruler, small ziplock plastic bag, foil or plastic wrap

Procedure:

Day 1

Use a knife to square off the ends of your potato. Your potato’s cells will act like the sailor’s cells.
Stand your potato on end & use your cork borers to bore 3 vertical holes.

Remove the potato cylinders from the cork borer & measure their length in centimeters.
Cut the 3 potato cylinders to the same length (about 4 -5 centimeters long).
Record the length & turgidity of the potato cylinders in your data table (day 1).
Place the 3 potato cylinders in a small ziplock bag to prevent them from dehydrating before they’re used.
Take 3 plastic cups and label them with the solution that will be placed in each one — sugar, salt, distilled water.
Prepare a saturated solution of salt by mixing as much salt as you can with water.
Repeat this step by making a saturated sugar solution.
Now fill each cup 2/3’s full of the correct solution —- sugar water, salt water, or distilled water.
Mass each of the potato cylinders & record this mass in grams on your data table.
Place one of your potato cylinders into each cup and cover the top of the cup with foil or plastic.
Leave the potato cylinders in the solution for 24 hours.

Day 2

Carefully remove the potato cylinder from the distilled water solution & pat it dry on a paper towel.
Measure the length of the potato cylinder & record this length & the appearance of the cylinder on your data table. (day 2)
Measure & record the mass of this cylinder.
Repeat steps 13-15 for the potato cylinders in the salt solution & the sugar solution.
Clean up your equipment & area and return materials to their proper place.

Data:

Results of Osmosis in Potato Cells
Solution	Initial length cm (day1)	Final length cm (day2)	Change in length cm	Initial Mass g (day1)	Final Mass g (day2)	Change in mass g	Initial Turgidity (flaccid or crisp)	Final Turgidity (flaccid or crisp)	Tonicity of Solution (iso-, hypo-, or hpertonic)
Distilled water
Salt Solution
Sugar Solution

Results & Conclusions:

1. Did any of the potato cylinders change in their turgidity (flexibility), and if so, which ones changed?

2. Explain why the flexibility of the potato slices changed.

3. Define isotonic, hypotonic, & hypertonic solutions.

4. If potato slices changed in length or turgidity, what process was responsible for this?

5. Make a sketch of your potato cylinder in the distilled water and use arrows to show the direction of water movement across the potato cell membranes.

6. What type of solutions were the salt & sugar solutions. Explain how you know this.

7. Which solution served as the control for this experiment & why?

8. In which solutions was their a greater solute concentration outside of the cells?

9. In which direction did water move through these cell membranes?

10. In what type of solution do plant cells do best & why?

11. Using the information you’ve discovered from this experiment, explain why the sailor died that drank saltwater.

BACK

Preap Cellular Respiration Study Guide

Cellular Respiration Review

1. Most eukaryotic cells produce only about ___________ ATP Molecules per Glucose Molecule.

2. What is the process by which glucose is converted to pyruvic acid? ________________________________________

3. At the beginning of aerobic respiration, pyruvic acid bonds to a molecule called ______________________________________ to form Acetyl CoA.

4. The breakdown of pyruvic acid in the presence of oxygen is called ______________________________ _______________________.

5. With every completion of the Krebs Cycle, how many ATP Molecules are made? ________________

6. What is the waste product of the Krebs Cycle? _____________________________________________.

7. The conversion of pyruvic acid to carbon dioxide and ethanol is called ___________________________________ _____________________________________________.

8. The release of energy from food molecules in the absence of oxygen is ______________________________________ _________________________________________________________.

9. What is the byproduct of the electron transport Chain?_______________________________________________.

10. How efficient is Anaerobic Respiration? __________% Aerobic Respiration? ____________%

11. What is the first pathway of cellular respiration called? ________________________________________________

12.What is the location of Glycolysis? _______________________________________________________

13. What is the scientific unit of Energy? ________________________________________________

14. What do you call cellular respiration in the presence of oxygen? _______________________________________ _________________________________________________________.

15. Yeast produces ______________________________ and _______________________________ in the process known as ____________________________________ ___________________________________________.

16. In cellular respiration, glycolysis proceeds the _______________________________ ___________________________.

17. In cellular respiration, more energy is transferred in the ___________________________ ________________________ _________________________________ than in any other step.

18. Glucose molecules are converted into _______________________________ _______________________ molecules in the process of glycolysis.

19. What is the location of the electron transport chain in prokaryotes? ________________ _______________________.

20. The processes of glycolysis and the anaerobic pathways is called ___________________________________.

21. What is the product of acetyl CoA and oxaloacetic acid? _________________ ___________________

22. What molecule is the electron acceptor of glycolysis? _________________________________________

23. The breakdown of organic compounds to produce ATP is known as ____________________________________ ________________________-_______________________________.

24. Glycolysis begins with glucose and produces ______________________________ _________________________.

25. An important molecule generated by both lactic acid and alcoholic fermentation is ______________________________.

26. In the first step of aerobic respiration, pyruvic acid from glycolysis produces CO2, NADH, H+, and _________________________________ _____________________________________.

27. The electron transport chain is driven by two products of the Krebs Cycle – ______________________ and ___________________________.

28. What happens to electrons as they are transported along the electron transport chain? _________________________________________________________________

29. The energy efficiency of aerobic respiration (including glycolysis) is approximately ______________ __________________________________________________.

30. Where in the mitochondria do the reactions of the Krebs cycle occur? _____________________________ ___________________________________________________________

31. Where in the mitochondria is the electron transport chain located? _____________________________ __________________________________________________

32. In alcoholic fermentation, ethyl alcohol is produced from _______________________________ ______________________________________.

33. ____________________________________, and _______________________________ supply electrons and protons to the electron transport chain.

34. Cellular respiration takes place in Two Stages: _______________________________________, then ________________________________________ ________________________________.

35. Water is an end product in the ________________________________________________________________
___________________________________________________________________.

36. In cellular respiration, a two-carbon molecule combines with a four-carbon molecule to form citric acid as part of the _____________________________________________________________________________________.

37. When glycolysis occurs, a molecule of glucose is ___________________________________________.

38. The name of the process that takes place when organic compounds are broken down in the absence of oxygen is _____________________________________________ or _______________________________________.

39. Energetic electrons that provide the energy for the production of most of a cell’s ATP are carried to the electron transport chain by _______________________________ and __________________________________________.

40. _______________________________________ is a biochemical pathway of cellular respiration that is anaerobic.

41. Glucose is split into smaller molecules during the biochemical pathway called __________________________________.

42. In the absence of oxygen, instead of oxidative respiration following glycolysis, glycolysis is followed by ______________________________________________________.

43. During fermentation, either ethyl alcohol and carbon dioxide or _______________________________________ is formed.

DIRECTIONS: Answer the questions below as completely and as thoroughly as possible. Answer the question in essay form (not outline form), using complete sentences. You may use diagrams to supplement your answers, but a diagram alone without appropriate discussion is inadequate.

1. How does aerobic respiration ultimately depend on photosynthesis?

2. Explain the role of oxaloacetic acid with respect to the cyclical nature of the Krebs cycle.

3. Glycolysis produces only 3.5% of the energy that would be produced if an equal quantity of glucose were completely oxidized. What has happened to the remaining energy in the glucose?

4. Why do most cells produce fewer than 38 ATP molecules for every glucose molecule that is oxidized through aerobic respiration?

5. What happens to electrons that accumulate at the end of the electron transport chain?

6. What role does chemiosmosis play in aerobic respiration?

7. What condition must exist in a cell for the cell to engage in fermentation?

8. How is the synthesis of ATP in the electron transport chain of mitochondria similar to the synthesis of ATP in chloroplasts?

9. The fourth step of glycolysis yields four ATP molecules, but the net yield is only two ATP molecules. Explain this discrepancy.

10. Under what conditions would cells in your body undergo lactic-acid fermentation?

11. What role does oxygen play in aerobic respiration? What molecule does oxygen become a part of as a result of aerobic respiration?

12. Where in the mitochondrion do protons accumulate, and what is the source of the protons?

Potato Osmosis Writeup

Potato Osmosis Lab Write up

Introduction

Explain the importance of water to the cell (60-90%, universal solvent, etc.)
Explain the parts of a solution (solute & solvent) and what is meant by the solution’s concentration
Discuss semipermeable cell membranes and osmosis
Explain what determines direction of movement of water into and out of the cell (solute concentration inside & outside the cell, water potential, down the concentration gradient, etc.)
Explain the effect of water loss and water gain on plant cells

Hypothesis
(write objective from lab.)

Materials
The materials used include …

Procedure
Day 1
Use a knife to … (No numbers; write in paragraph form)

Procedure
Day 2
Carefully remove the … (No numbers; write in paragraph form)

Results

Data Table

1. Did any of the …
answer

Conclusion

Restate the hypothesis
Discuss the original mass and original appearance of the potato cores
Discuss the mass change (if any0 and flexibility of the cores after 24 hours in the solutions
Explain the change of mass in each core telling WHY THE MASS CHANGE OCCURRED (movement of the water & in which direction & why it moved that way)
Explain the change in flexibility of the cores (why were they stiffer or more flexible)
Make a final statement about concentration gradient & movement of water across cell membranes