Curriculum Map 143 - BIOLOGY JUNCTION

Floating Leaf Disk Assay

The Floating Leaf Disk Assay for Investigating Photosynthesis

Brad Williamson

Introduction:

Trying to find a good, quantitative procedure that students can use for exploring photosynthesis is a challenge. The standard procedures such as counting oxygen bubbles generated by an elodea stem tend to not be “student” proof or reliable. This is a particular problem if your laboratory instruction emphasizes student-generated questions. Over the years, I’ve found that the floating leaf disk assay technique to be reliable and understandable to students. Once the students are familiar with the technique they can readily design experiments to answer their own questions about photosynthesis. I plan to add to this page as I have time to elaborate on the technique and provide suggestions for modifications.

Materials:

1. Sodium bicarbonate (Baking soda)

2. Liquid Soap

3. Plastic syringe (10 cc or larger)—remove any needle!

4. Leaf material

5. Hole punch

6. Plastic cups

7. Timer

8. Light source

Optional:

Buffer Solutions

Colored Cellophane or filters

Leaf material of different ages

Variegated leaf material

Clear Nail polish

Procedure:

Prepare 300 ml of bicarbonate solution for each trial.
1. The bicarbonate serves as an alternate dissolved source of carbon dioxide for photosynthesis. Prepare a 0.2% solution. (This is not very much—it’s about 1/8 of a teaspoon of baking soda in 300 ml of water.) Too much bicarbonate will cause small bubbles (CO2)to form on the surface of the leaf which will make it difficult to sink the leaf disk.
2. Add 1 drop of dilute liquid soap to this solution. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf. It’s difficult to quantify this since liquid soaps vary in concentration. Avoid suds. If your solution generates suds then dilute it with more bicarbonate solution.

Cut 10 or more uniform leaf disks for each trial

1. Single hole punches work well for this but stout plastic straws will work as well
2. Choice of the leaf material is perhaps the most critical aspect of this procedure. The leaf surface should be smooth and not too thick. Avoid plants with hairy leaves. Ivy, fresh spinach, Wisconsin Fast Plant cotyledons—all work well. Ivy seems to provide very consistent results. Any number of plants work. My classes have found that in the spring, Pokeweed may be the best choice.
3. Avoid major veins.

Infiltrate the leaf disks with sodium bicarbonate solution.

1. Remove the piston or plunger and place the leaf disks into the syringe barrel. Replace the plunger being careful not to crush the leaf disks. Push on the plunger until only a small volume of air and leaf disk remain in the barrel (< 10%).

1. Pull a small volume of sodium bicarbonate solution into the syringe. Tap the syringe to suspend the leaf disks in the solution.

1. Holding a finger over the syringe-opening, draw back on the plunger to create a vacuum. Hold this vacuum for about 10 seconds. While holding the vacuum, swirl the leaf disks to suspend them in the solution. Let off the vacuum. The bicarbonate solution will infiltrate the air spaces in the leaf causing the disks to sink. You will probably have to repeat this procedure several times in order to get the disks to sink. You may have difficulty getting the disks to sink even after applying a vacuum three or four times. Generally, this is usually an indication that you need more soap in the bicarbonate solution. Some leaf surfaces are more water repellent than others are. Adding a bit more soap usually solves the problem.

Pour the disks and solution into a clear plastic cup. Add bicarbonate solution to a depth of about 3 centimeters. Use the same depth for each trial. Shallower depths work just as well.

1. This experimental setup includes a control. The leaf disks in the cup on the right were infiltrated with a water solution with a drop of soap—no bicarbonate.

Place under the light source and start the timer. At the end of each minute, record the number of floating disks. Then swirl the disks to dislodge any that are stuck against the sides of the cups. Continue until all of the disks are floating.

1. The control is on the left in each image. In the experimental treatment, on the right, leaf disks are rising and floating on the surface.

Sample results:

Time (minutes)	Disk Floating
1	0
2	0
3	0
4	0
5	0
6	0
7	1
8	1
9	1
10	1
11	4
12	7
13	8
14	10

The point at which 50% of the leaf disks are floating is the point of reference for this procedure. By interpolating from the graph, the 50% floating point is about 11.5 minutes. Using the 50% point provides a greater degree of reliability and repeatability for this procedure.

Genetic Problems Solutions Campbell Ch14

Genetics Problems Campbell 1. A man with hemophilia (a recessive , sex-linked condition has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will be a hemophiliac? A son? If the couple has four sons, what is the probability that all four will be born with hemophilia?

Solution

2. Pseudohypertropic muscular dystrophy is a disorder that causes gradual deterioration of the muscles. It is seen only in boys born to apparently normal parents and usually results in death in the early teens. (a) Is pseudohypertrophic muscular dystrophy caused by a dominant or recessive allele? (b) Is its inheritance sex-linked or autosomal? (c) How do you know? Explain why this disorder is always seen in boys and never girls.

Solution

3. Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color-blind. (a) What is the probability that they will have a color-blind daughter? (b) What is the probability that their first son will be color-blind? (Note: the two questions are worded a bit differently.)

Solution

4. A wild-type fruit fly (heterozygous for gray body color and normal wings was mated with a black fly with vestigial wings. The offspring had the following phenotypic distribution: wild type, 778; black-vestigial, 785; black-normal, 158; gray-vestigial, 162. What is the recombination frequency between these genes for body color and wing type.

Solution

5. In another cross, a wild-type fruit fly (heterozygous for gray body color and red eyes) was mated with a black fruit fly with purple eyes. The offspring were as follows: wild-type, 721; black-purple, 751; gray-purple, 49; black-red, 45. (a) What is the recombination frequency between these genes for body color and eye color? (b) Following up on this problem and problem 4, what fruit flies (genotypes and phenotypes) would you mate to determine the sequence of the body color, wing shape, and eye color genes on the chromosomes?

Solution

6. A space probe discovers a planet inhabited by creatures who reproduce with the same hereditary patterns as those in humans. Three phenotypic characters are height (T = tall, t = dwarf), hearing appendages (A = antennae, a = no antennae), and nose morphology (S = upturned snout, s = downturned snout). Since the creatures were not “intelligent” Earth scientists were able to do some controlled breeding experiments, using various heterozygotes in testcrosses. For a tall heterozygote with antennae, the offspring were tall-antennae, 46; dwarf-antennae 7; dwarf-no antennae 42; tall-no antennae 5. For a heterozygote with antennae and an upturned snout, the offspring were antennae-upturned snout 47; antennae-downturned snout, 2; no antennae-downturned snout, 48: no antennae-upturned snout 3. Calculate the recombination frequencies for both experiments.

Solution

7. Using the information from problem 6, a further testcross was done using a heterozygote for height and nose morphology. The offspring were tall-upturned nose, 40; dwarf-upturned nose, 9; dwarf-downturned nose, 42; tall-downturned nose, 9. Calculate the recombination frequency from these data; then use your answer from problem 6 to determine the correct sequence of the three linked genes.

Solution

8. Imagine that a geneticist has identified two disorders that appear to be caused by the same chromosomal defect and are affected by genomic imprinting: blindness and numbness of the limbs. A blind woman (whose mother suffered from numbness) has four children, two of whom, a son and daughter, have inherited the chromosomal defect. If this defect works like Prader-Willi and Angelman syndromes, what disorders do this son and daughter display? What disorders would be seen in their sons and daughters?

Solution

9. What pattern of inheritance would lead a geneticist to suspect that an inherited disorder of cell metabolism is due to a defective mitochondrial gene?

Solution

10. An aneuploid person is obviously female, but her cells have two Barr bodies. what is the probable complement of sex chromosomes in this individual?

Solution

11. Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B, 8 map units; A-C, 28 map units; A-D, 25 map units; B-C , 20 map units; B-D, 33 map units.

Solution

12. About 5% of individuals with Downs syndrome are the result of chromosomal translocation. In most of these cases, one copy of chromosome 21 becomes attached to chromosome 14. How does this translocation lead to children with Down syndrome?

Solution

13. Assume genes A and B are linked and are 50 map units apart. An individual heterozygous at both loci is crossed with an individual who is homozygous recessive at both loci. (a) What percentage of the offspring will show phenotypes resulting from crossovers? (b) If you did not know genes A and B were linked, how would you interpret the results of this cross?

Solution

14. In Drosophila, the gene for white eyes and the gene that produces “hairy” wings have both been mapped to the same chromosome and have a crossover frequency of 1.5%. A geneticist doing some crosses involving these two mutant characteristics noticed that in a particular stock of flies, these two genes assorted independently; that is they behaved as though they were on different chromosomes. What explanation can you offer for this observation?

Solution

BACK

Campbell Chapter 14 Gen Prob 1

Molecular Genetics: Problem 1A man with hemophilia (a recessive , sex-linked condition has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will be a hemophiliac? A son? If the couple has four sons, what is the probability that all four will be born with hemophilia?

Genotypes:

A man with hemophilia is XhY where h = hemophilia gene and H = the normal gene.
Any daughter with normal phenotype whose father has hemophilia will be a carrier.

Her genotype must be:

XhXH and NOT XHXH We can use a Punnett square to show the probability of a daughter or son having hemophilia.

daughter x normal manXhXH x XHY

A. If the daughter marries a normal male the probability of a daughter having hemophilia is zero.

B. About 50% of male children would have hemophilia (Boxes 2 and 4 above)

C. The probability that all 4 sons have inherited hemophilia would be: 1/2 x 1/2 x 1/2 x 1/2 or 1/16.

BACK

Genetic Disorder Project Presentation

Genetic Disorders to Present

Internet resources to help in research

Rubric for project

You have been challenged to incorporate your knowledge about cells, cell division, genetics, and DNA to research and present on a specific genetic disorder. You have already completed your basic study about the ideas of genetics and mutations. Now with the information that you have you are being asked to research a specific genetic disorder and give an oral presentation along with creating either a PowerPoint or poster to explain the genetic disorder.

Your multimedia presentation (powerpoint / poster) along with your oral presentation
should include the following points.

What is the name of the disorder and what is the history behind the disorder? Who discovered it or/and who have done research on the disease?
How is the disorder diagnosed? How does a person receive the disorder? Is it sex-linked? Is it a mutation? Is it due to heredity?
You will need to find out all of the signs and symptoms of the given disorder and share these with the class.
What types of treatment there are for the disorder?
Include a suggested list of readings and/or Internet sources that may be of interest to the class.
You are encouraged to share any other information that you feel is relevant that you feel is important for others to know about the genetic disorder.

List of possible Genetic Disorders to Present:
Achondroplasia (Dwarfism) Albinism Adrenal hyperplasia Autism/ Asperger syndrome Cystic Fibrosis Down Syndrome (Trisomy 21) Duchenne Muscular Dystrophy Familial Dysautonomia Gardner syndrome (intestinal polyposis) Gaucher’s Disease Hemophilia Huntington’s Disease Jacobsen Syndrome Klinefelters Syndrome Klippel-Feil Syndrome	Leukodystrophy Lou Gehrig’s Disease (ALS) Marfan Syndrome Moebius Syndrome Polycystic Kidney Disease Progeria Proteus Syndrome Retinoblastoma Rett’s Syndrome Spinocerebellar Ataxia Tay-Sachs Disease Tourette Syndrome Turner Syndrome

List of internet resources that may be helpful to you in creating your presentation:

Yahoo – Genetic Disorders http://dir.yahoo.com/Health/Diseases_and_Conditions/Genetic_Disorders/.
Site explains several different disorders and contains links to all of the different types of genetic disorders.

Genetic & Rare Conditions Sitehttp://www.kumc.edu/gec/support/.
links to different types of disorders in alphabetical order.

What can our chromosomes tell us? http://biology.about.com/science/biology/gi/dynamic/offsite.htm?site=http://gslc.genetics.utah.edu/.
A site that talks about karyotyping of genotypes.

Genetic Disorder Library
http://learn.genetics.utah.edu/units/disorders/whataregd
To learn more about different genetic disorders, browse through the Genetic Disorder Library.

A Genetics Glossary http://biology.about.com/science/biology/gi/dynamic/offsite.htm?site=http://helios.bto.ed.ac.uk/bto/glossary/index.html
A basic genetic glossary.

Genetics Education Center http://www.kumc.edu/gec/.
Seeks to help educate people about genetics.

The National Human Genome Research Institute http://www.nhgri.nih.gov/.
Explains about the human genome project.

Department of Energy – Human Genome Project Information http://www.ornl.gov/hgmis/.
Provides a lot of information about the human genome project.

A Gene Map of the Human Genome http://www.ncbi.nlm.nih.gov/science96/.
You can see the mapping of several different chromosomes found within the body.

Learning about the Human Genome Project and Genetics through the World Wide Web http://www.kumc.edu/gec/hgpwww.html.
Looks at the ethical issues of genetic research.

Understanding Gene Testinghttp://www.accessexcellence.org/ae/AE/AEPC/NIH/index.html.
This site talks of how genes are linked to disease and how a gene creates a genetic disorder.

Basics of DNA Fingerprintinghttp://www.biology.washington.edu/fingerprint/dnaintro.html.
Explains the basic understanding of DNA fingerprinting.

What is Genetic Testing? http://www.lbl.gov/Education/ELSI/Frames/genetic-testing-f.html.
Shows the basics of genetic testing and talks about the ethical issues of that happen due to genetic testing.

Rubric for Evaluation of Genetic Disorder Presentation.

Beginning 5 points	Developing 10 Points	Accomplished 15 Points	Exemplary 20 Points	Total Score
Oral Presentation Quality of Information	Bare minimums have been accomplished. Little understanding about the genetic disorder delivered in oral presentation. Could only read slides with no further understanding.	Minimums plus slight extras added. Answered questions from the intro and at least one question posed to them in the process section.	All information present and complete. Some problems with flow and delivery. Shows more or less some understanding of knowledge – has minor flaws.	Information is well thought out, flows well, all information is completed, Appears to have been practiced, knowledge shown.
Bibliography Amount of additional Information for reading and websites found and presented	no additional reading lists or websites provided or presented in bibliography.	At least 2 web sites or books accessed and verified in presentation and presented in bibliography.	At least 4 web sites or books accessed and verified in presentation and presented in bibliography.	At least 6 web sites or books accessed and verified in presentation and presented in bibliography.
Organization of presentation	Random information is presented	Disorganized at times.	Organized	Organized effectively with easy understanding.
Use of class time working on project	Majority of class time was wasted.	Half of class time was wasted.	Little class time was wasted.	No class time was wasted.
Overall Multimedia Presentation	Disorganized Not Completed Missing Key Component Questions no graphics.	Spelling errors present presentation has some flow to it but is choppy.	Easily understood by all. Includes graphics and data tables of information retrieved.	Neatly done, organized, proper spelling, allparts included,above and beyond effort. Information that is presented is aesthetically pleasing to the eye.
Link to printable rubric in word document format Link to Bibliography Citation Machine				TOTAL SCORE

Sponge Coloring Diagram and Questions

Found at the Biology Corner Name __________________ Period ______

Sponges – A Coloring Worksheet

Since sponges look like plants, it is understandable why early biologists thought they were plants. Today, we know that sponges are simple, multicellular animals in the Kingdom Animalia, Phylum Porifera. This phylum is thought to represent the transition from unicellular animals to multicellular animals. Most (but not all) sponges are asymmetrical and have no definite shape. Sponges, like all animals, are eukaryotic – meaning their cells have a nucleus. Porifera in Latin means “pore-bearer” and refers to the many pores or openings in these animals. Because of these pores, a sponge can soak up and release water. At one time, real sponges were used for cleaning and bathing. Today, most are artificially made.

All adult sponges are sessile, meaning they are attached to some surface. Since they cannot move, sponges cannot pursue their food. Instead, they are filter feeders, meaning they obtain their food by straining the water for small bits of food like bacteria, algae or protozoans.

Sponges exhibit less specialization (adaptation of a cell for a particular function) of cells than most invertebrates. The primitive structure of a sponge consists of only two layers of cells separated by a non-living jelly like substance. The outer layer of the sponge is the epidermis which is made of flat cells called epithelial cells. Color all the epithelial cells (B) of the epidermis peach or pink.

The inner layer consists of collar cells (A) whose function is to circulate water through the sponge. They do this by swishing their flagella which pulls water through the incurrent pore – water then travels out the osculum at the top of the sponge. As water passes through the sponge in this way, cells absorb food and oxygen and waste is excreted. Color the osculum (D) dark blue, the incurrent pores (C) light blue. Color the inside of the sponge where water circulates the same light blue as you colored the incurrent pores. Color all the collar cells (A) red.

In the jelly-like substance between the epidermis and the collar cells are cells called amebocytes – because they look like amebas. The job of the amebocytes is to travel around distributing food and oxygen to the cells of the epidermis. Because of the amebocytes, scientists believe that sponges evolved from protists. Color all of the amebocytes (E) green – look for them carefully.

The body of the sponge would collapse if it did not have some type of supporting structure. Some sponges have a soft network of protein fibers called spongin. Others have tiny, hard particles called spicules. Many of these spicules also stick out of the epidermis and provide the sponge with protection. Most sponges have a combination of spicules and spongin, the ratio often determines how soft or hard the sponge is. Search for and color all the pointy spicules (F) brown.

Reproduction for sponges can be accomplished both sexually and asexually. There are three ways for a sponge to reproduce asexually: budding, gemmules, and regeneration. Sponges can simply reproduce by budding, where a new sponge grows from older ones and eventually break off. Color the adult sponge (J) pink and all the buds (G) you can find red. Sponges can also reproduce by regeneration, where missing body parts are regrown. People who harvest sponges often take advantage of this by breaking off pieces of their catch and throwing them back in the water, to be harvested later. Finally, sponges can reproduce by creating gemmules – which is a group of amebocytes covered by a hard outer covering. Color the gemmule (H) yellow.

Sexual reproduction occurs when one sponge releases sperm into the water. This sperm travels to another sponge and fertilizes its eggs. The larva form will then swim to another location using its flagella where it will grow into an adult sponge. Most sponge species are hermaphrodites, they can produce both eggs and sperm.

Questions:

1. What did early biologists think sponges were? ______________________

2. Sponges belong to the Kingdom _________________ and the Phylum _______________

3. Sponges are [ unicellular or multicelluar ] and [ prokaryotic or eukaryotic ]

4. What type of symmetry do sponges have? ___________________________________

5. What does it mean to be sessile? ____________________________________

6. How do sponges get their food? ___________________________________

7. Water enters the sponge through the _____________________ and leaves through the
_____________________.

8. What is the job of the amebocyte? ________________________________________

9. What two substances give the sponge support? _________________________________

10. Tiny sponges growing from the main body of the sponge are called _________________

11. What is a gemmule? ___________________________________________________

12. What is a hermaphrodite? ______________________________________________

Label the letters on the diagrams

SciSpongesColoringWSP3.bmp (1403574 bytes)

Label the letters on the diagrams
SciSpongesColoringWSP4.bmp (2585142 bytes)

Found at www.biologycorner.com