SUBJECT: Corn genetics

DATE: 2/97

 

I'm hoping someone can give me suggestions on a corn genetics lab. I'm

looking for a hands on/ minimal prep genetics lab for intro bio students.

I've been looking at the corn ears available through Ward's or Carolina and

wondering if they might do the trick. Has anyone used these and had a

positive experience (or even a negative one might help)?

 

Thanks,

Brenda Simmers

Lab Coordinator

Dept. of Biology

University of Toledo

 

 

I've used a couple of the commercial corn products for intro genetics

labs with reasonable success. The first are Carolina's boxed mounts

showing simple crosses: P, F1, and F2 generations. They're static and

not very interactive, but they graphically illustrate how recessive

alleles are masked but not destroyed, which I've found needs

reinforcement for beginners.

 

The whole cobs they sell are very good for introducing chi square

analyses. You can get monohybrid and dihybrid ears in various ratios

that allow students to evaluate hypotheses as to what the parental

crosses may have been. Since I find that they have a very hard time

getting chi square analysis straight, it's really nice to have a

sample that's so simple to work with. If they had to worry about

breeding and scoring complex traits too, they never would get to the

statistics! So for non-majors and beginning majors, I think they can

be a pretty good tool.

 

One thing though - if you're going to get the whole cobs, I strongly

suggest you buy them from Wards and not Carolina. The cobs of "sealed

and fumigated" corn I bought from Carolina turned out to be full of

moths. I replaced them with corn from Wards and now store them in

Rubbermaid boxes full of moth balls.

 

John Dickerman

Northern Illinois University

T80JWD1@WPO.CSO.NIU.EDU

 

 

Brenda,

 

If you are trying to teach Mendelian inheritance and/or related

statistics, then the corn works great. Carolina (and Wards too,

probably) will even send you written material that provides all the

information students need to do the lab work

 

I recommend adding some human traits for interest purposes. But the

corn sure cuts down on the prep compared to a fly lab for example,

unless you have fly cultures available from a genetics course or a

research lab.

 

Good luck,

 

Dave McNeely, Biology, University of Texas at Brownsville, 80 Fort

Brown, Brownsville, TX 78520; mcneely@utb1.utb.edu

 

 

I used corn to teach Mendelian genetics for the first time this year and

was happy with the results. I had the students first look at a monohybrid

cross, and then secondarily at a dihybrid cross. I incorporated a

hypothesis making and testing component to it and also had the students

give me the expected phenotypic and genotypic ratios for the dihybrid cross

if the traits were assorting independently or were linked. Next year I

think I'll make them draw chromosomes going through meiosis as well, since

too many of my students still fail to make a connection between meiosis and

mendelian genetics. If you want to see the questions I ask, let me know.

Mary

p.s. we found that our students "picked" at the corn when they got bored so

we had to put shrink wrap on all our ears.

 

 

Mary H. Gray D.V.M.

Department of Biological Sciences

Lilly Hall of Life Science

Purdue University

West Lafayette, IN 47907

(317)-494-8185

FAX (317)-494-0876

 

 

Dear Brenda:

We use the corn ears for monohybrid and dihybrid crosses and then do some

population genetics with albino seedlings. You can obtain seeds of

different F generations (which sprout in 1-2 weeks)

from Carolina and see how the number of albino seedlings

decreases with each generation. The students prefer counting seedlings

to corn kernels, although it is still tedious. Each generation has a

different expected ratio which can be determined on a table available from

Carolina Biological (Population Genetics biokit).

 

Kathy Gallucci

Elon College

 

 

Brenda:

Yes, I use dihybrid corn ears to do a genetics/chi square lab. If you're

interested, I even have a multimedia program I've written to go along with it;

it's described in the Journal of College Science Teaching, March 1996. You can

write to my email address if you'd like to learn more about it:

MOSSRE@WOFFORD.EDU

The lab is very, very easy to do; but the students usually have trouble

with the statistics. That's why I wrote the program.

-Bob Moss

Wofford College

 

 

The corn (dihybrid) results are good for Chi square practice, also.

 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Jean DeSaix, Ph.D.

Department of Biology Coker Hall CB#3280

University of North Carolina at Chapel Hill, NC 27599-3280

Work Phone: 919-962-1068 Home Phone 919-929-1580

FAX 919-962-1625 email jdesaix@email.unc.edu

 

 

Brenda, We keep the 3:1 corn ears in the lab as a backup for the 3:1

albino corn plants. On occassion they don't grow or don't survive the

entire week. In that case, we have the students use the ears of corn to

figure out the ratio. It isn't exciting, but it is easy. The only problem

is that students will occassionally write on the kernels or "shuck the

corn". --cmw

 

Charlene M. Waggoner, Ph.D.

Department of Biological Sciences

Bowling Green, State University

Bowling Green, OH 43403

 

 

Brenda

 

We also had problems with students getting bored with counting the

kernels and then proceeding to picking at them. They found human

traits to be much more interesting.

 

One word of warning on keeping the ears - I made the mistake of

putting them away in drawers. I didn't know that our building had

house mice who were able to access the drawers from the back. The

mice fed well and we were out all the ears of corn!

 

Lynn

**************************************************

Lynn Ruxton (Lynn.Ruxton@lakeheadu.ca)

Department of Biology

Lakehead University

Thunder Bay, ON, Canada P7B 5E1

 

 

For all those that are trying to keep ears, the best place is in the freezer.

 

Beth Morgan

Plant Biology

U of Illinois

 

 

Brenda, we've used them to demonstrate dihybrid crosses (color-yellow or

purple-- and kenel texture-smooth or wrinkled) and found them to be

close to the 9:3:3:1 phenotype ratio

 

From: Keith Overbaugh <koverbau@nmc.edu>

 

I teach an advanced biology class for high school seniors. When dealing

with genetics I use ears of corn to not only look at the Mendelian ratios

but as a way of introducing gene interaction as seen in ratios such as 12

purple: 3 yellow: 1 white or 9 yellow: 3 white: 4 purple and to look at the

work of Barbara McClintock and transposons using ears of "Indian corn".

My materials were developed for high school students but could no doubt be

modified for any group of students.

Thanks for the tips on storing the ears--I haven't had a problem to date

perhaps since our facility is new but will insure they are safely stashed

in the freezer.

Judy Hodges

Derby High School

920 N. Rock Road

Derby, Kansas 67037

316-788-8500

 

 

We use the ears of corn to study Mendelian Genetics and simple genetic

traits. I know that some of the students are a little bored with counting

kernels we limit the number they have to count and include our

introduction to the Chi-square test during this lab. Depending on your

students, they will probably benefit from this exercise - many of them do

not understand gametogenesis and setting-up Punnett squares, or the

connection between genotype and phenotype. Also, the fact that "science"

is not always exciting.

 

In our lab the students all do a monohybrid cross of either color or

texture and a dihybrid cross of both. In addition we give them an

"unknown" and ask them to determine the genotypes of the parents that

"formed" the ear. (We usually use the results of a test cross for the

unknown.)

 

One hint for storage, we ended up with a serious moth infestation and

started storing the corn ears in plastic buckets, the ones that preserved

specimens come in work great, with a few moth balls. We lost many ears,

and had to deal with a major nuisance, before we started storing them this

way.

 

Rosemary

 

**********************************************************

Rosemary E. Boone Department of Biological Sciences

rmboone+@pitt.edu University of Pittsburgh

(412) 624-9325 G2 Clapp Hall

Fax: (412) 624-4759 Pittsburgh, PA 15260

**********************************************************

 

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