Corn

(Zea mays)

Presented by Gaby Negron

Did you know?

When we think of corn it's normal to picture one that is pure yellow, but there is a variant of Zea mays called "Flint corn" that naturally grows in many different colors! It is usually used for decorative purposes, but it is edible.

Domestication

Teosinte is corn's wild ancestor that began to be bred in southern Mexico about 9,000 years ago.

Modern corn is completely domesticated. It cannot survive in the wild now. Humans, through selective breeding, have stripped away its mechanisms for reproduction and seed dispersal.

Genome characteristics of corn

Diploid organism where 2n= 20 chromosomes
It has about 32,000 to 40,000 genes in its genome.
Of that, about 85% of those are transposons.
Each kernel of the cob is an individual that resulted from its own distinct reproduction event.

Remember the Grabber?

Well, the color variation of corn kernels is caused by genetic material exchange, more specifically by transposons.

What are Transposons?

Transposons are genes that move from 1 part of the chromosome to another part.
Through its movement, it changes DNA and can promote or inhibit functions of nearby genes.
It provides unexpected diversity to genomes, because it can lead to advantageous or disadvantageous trait expression.

How were transposons discovered?

Dr. Barbara McClintock

Did her experiments in the 1940s
She used corn as her subject to show how genes could be responsible for turning physical traits on or off.
Had planted thousands of cobs in her quest to figure out how the physical traits of Flint corn were being inherited and displayed.

Experiment and Findings

Realized that chromosomes were experiencing breakage at certain locations in the corn.
Analyzed relationship between the chromosome alterations and the color of the kernels.
Ultimately, relationships were indeed found. Most importantly, on chromosome 9, there were 2 transposons discovered.
Transposon "Ds" breaks the chromosome and inhibits other nearby genes as it moves around.
Transposon "Ac" had to be present on the chromosome to activate Ds to jump.
The interactions of Ds and Ac were responsible for the color pattern off each kernel.

For example:

The dominant allele "Bz" produces a phenotype of a solid purple kernel. If the pigment production is not stabilized like in the recessive "bz" it produces a phenotype of a bronze colored kernel.

When transposons Ds and Ac are present, the state of the allele is disrupted and repaired→ the kernel is bronze with purple spots
When transposon Ds is present only, the state of the allele is permenently disrupted→ the kernel is only bronze
When there is no transposon Ds, the state of the allele is functional and together→ the kernel is solid purple

Human selection

Humans have acted as a force for thousands of years by selecting corn to be bred to produce higher yields, taste sweeter, withstand pests, etc.
Before this was done by saving the seeds that exhibited desired traits to then further propagate those alleles.
Now there are additional methods of artificial selection. Such as, genetic engineering.

An example of genetically engineered corn:

BT corn

Named after Bacillus thuringiensis, a bacteria species that lives in the soil.
The bacteria synthesizes proteins that poisons selected groups of insect pests upon consumption but doesn't harm mammals.
Genes of B. thuringiensis are inserted into the corn's genome and from there the corn produces the proteins warding pests from eating/damaging the crop.

Variability:

Sweet corn

Flint corn

Pop corn

There are many different variants of corn, each with their own uses and specialties.

Sweet corn
Flint corn
Pop corn
Dent corn
Flour corn
Waxy corn

Dent corn

Flour corn

Waxy corn

Sweet corn

Contains more sugar compared to other corn types
Harvested at its immature stage when its kernels are soft and tender

Flint corn

Has a characteristically hard outer shell
Naturally comes in many different colors
Used as decoration during Autumn
Ground into cornmeal when used for food

Pop corn

A subtype of flint corn with smaller kernels
When heated, the built-up pressure makes it explode from its hard shell to reveal the starchy center

Dent corn

Used as animal feed
Made into biofuel/ethanol
Used as a sweetener when it's corn syrup
Used in baking as an oil

Flour corn

Ground into corn flour and used in many ways for cooking and baking.
Such as, to bread food and make it crunchy, and as a primary ingredient to making meals like pupusas and tortillas.
Used in gluten-free recipes as a standard flour substitute

Waxy corn

Has 100% amylopectin starch compared to others' approx. 73%
This makes it harder for this corn to break down when it's frozen
It is used as a thickening agent in foods
As well as an adhesive agent in the tape and paper industry

Overall relationship with humans:

History

Provided food stability to nomadic ancestors
Corn was easy to store which led to food being saved for later times
This helped settlements prosper from the reliable harvests corn produced.

Food

Can be eaten on its own
Can be made into corn syrup, corn flour, and corn oil.
Some everyday examples of foods made with these ingredients: Chips, tortillas, cereals, sodas, candies, bakery goods, fried foods, etc.

Economy

Corn is the primary feed grain exported in the United States.
It is used in a multitude of different ways besides human food.
Feeding animals, ingredient in biofuel, used in soaps and cosmetics, works as an adhesive glue, etc.

References:

“All about Popcorn.” Different Types of Corn, www.popcorn.org/All-About-Popcorn/Different-Types-of-Corn. Accessed 2 June 2026.

“Barbara McClintock.” Wikipedia, Wikimedia Foundation, en.wikipedia.org/wiki/Barbara_McClintock. Accessed 14 June 2026.

Bergtrom, Gerald. “14.3: The ‘jumping Genes’ of Maize.” Biology LibreTexts, Libretexts, 27 May 2022, bio.libretexts.org/Under_Construction/Cell_and_Molecular_Biology_(Bergtrom)/14%3A_Repetitive_DNA_A_Eukaryotic_Genomic_Phenomenon/14.03%3A_The_’Jumping_Genes’_of_Maize.

Bessin, Ric. “Bt-Corn: What It Is and How It Works.” Entomology, entomology.mgcafe.uky.edu/ef130. Accessed 15 June 2026.

Colonna, Federica Turriziani. “Barbara McClintock’s Transposon Experiments in Maize (1931–1951).” Barbara McClintock’s Transposon Experiments in Maize (1931–1951) | Embryo Project Encyclopedia, Arizona State University, 9 Feb. 2017, embryo.asu.edu/pages/barbara-mcclintocks-transposon-experiments-maize-1931-1951.

“Corn and Other Feed Grains - Feed Grains Sector at a Glance.” Corn and Other Feed Grains - Feed Grains Sector at a Glance | Economic Research Service, www.ers.usda.gov/topics/crops/corn-and-other-feed-grains/feed-grains-sector-at-a-glance. Accessed 2 June 2026.

The Corn Crop NCH-10 Origin, Adaptation, and Types of Corn, corn.agronomy.wisc.edu/Management/pdfs/NCH10.pdf. Accessed 2 June 2026.

Corn Genetics: Hip Hop Genes | Carolina Biological Supply, www.carolina.com/teacher-resources/Interactive/corn-genetics-hip-hop-genes/tr10692.tr. Accessed 14 June 2026.

Corn: A Fruit, Vegetable, Grain, or All Three? Item Type Pamphlet; Text Authors, repository.arizona.edu/bitstream/handle/10150/670003/AZ1915-2021.pdf?sequence=1&isAllowed=y. Accessed 2 June 2026.

“Different Types of Corn & How They Are Used.” American Farm Bureau Foundation for Agriculture, www.agfoundation.org/news/different-types-of-corn-how-they-are-used. Accessed 2 June 2026.

Everything You Ever Wanted to Know about Indian Corn | Howstuffworks, recipes.howstuffworks.com/everything-about-indian-corn.htm. Accessed 2 June 2026.

Fell, Andy. “Tracking down the Jumping Genes of Maize.” UC Davis, 2 May 2019, www.ucdavis.edu/news/tracking-down-jumping-genes-maize.

“GMO Crops, Animal Food, and Beyond.” U.S. Food and Drug Administration, FDA, www.fda.gov/food/agricultural-biotechnology/gmo-crops-animal-food-and-beyond. Accessed 15 June 2026.

Hellmich, Richard L, and Kristina Allyse Hellmich. “Use and Impact of Bt Maize.” Nature News, Nature Publishing Group, 2012, www.nature.com/scitable/knowledge/library/use-and-impact-of-bt-maize-46975413/.

“Indian Corn.” Wisconsin Horticulture, hort.extension.wisc.edu/articles/indian-corn/. Accessed 2 June 2026.

“Maize.” Wikipedia, Wikimedia Foundation, 8 May 2026, en.wikipedia.org/wiki/Maize.

“Nobel Prize in Physiology or Medicine 1983.” NobelPrize.Org, www.nobelprize.org/prizes/medicine/1983/press-release/. Accessed 14 June 2026.

Pray, Leslie, and Kira Zhaurova. “Barbara McClintock and the Discovery of Jumping Genes (Transposons).” Nature News, Nature Publishing Group, 2008, www.nature.com/scitable/topicpage/barbara-mcclintock-and-the-discovery-of-jumping-34083/.

“Top Little Did You Know Corn Facts.” Nestlé Cereals, www.nestle-cereals.com/uk/blog/healthy-breakfast/top-facts-about-corn. Accessed 2 June 2026.

Wurm, Nick. “Barbara McClintock’s Corn.” Cold Spring Harbor Laboratory, 9 July 2024, www.cshl.edu/harborscope/barbara-mcclintocks-corn/.

Page updated

Google Sites

Report abuse