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The Tumor That Grows Teeth

High school learnscience.org

Name Date

Predict

Your body has many kinds of cells, like skin cells, bone cells and nerve cells. Some tumors grow in an ovary, the organ where eggs form. Could a tumor in an ovary grow a tooth?

Circle one. Yes / No

Why?

Watch

  1. My ovary tumor grows teethyoutube.com/shorts/zf0GQxCVDcI

Word of the day

Teratoma (ter-uh-TOH-muh). A tumor made up of different types of tissue.

Word partComes fromMeaning
terat-Greek térasmonster, marvel
-omaGreektumor, swelling
  • Terabyte starts with tera-, from the same Greek word, téras. In units of measure, tera- means one trillion.
  • Doctors use -oma in many tumor names, like melanoma and carcinoma.

Bonus words. Dermoid (DUR-moid) means skinlike, from derm-, “skin,” and -oid, “like.” Homozygous (ho-mo-ZY-gus) describes a matching pair, from homo-, “same.” Heterozygous (het-er-oh-ZY-gus) describes a mixed pair, from hetero-, “different.”

Questions

  1. In the video, Raven says a sperm does two separate jobs at fertilization. It delivers the father’s chromosomes, and it activates the egg to start dividing. A dermoid cyst grows from a single germ cell, a cell on its way to becoming an egg. When a dermoid cyst starts, there’s no sperm at all. Which sperm job still happens, and which one never does?

    Hint. Think about whose chromosomes end up in the dermoid cyst’s cells.

  2. The cells of a dermoid cyst all come from one starting cell, and they carry the same chromosomes. Yet one cyst can hold skin, fat, cartilage and teeth. How can cells that carry the same DNA become such different tissues?

    Hint. Think about what cells do after they divide. Do skin cells and fat cells use the same genes?

  3. Your body is organized in levels. Cells form tissues, tissues form organs, and organs work together in organ systems. Scientists who study dermoid cysts describe the tissues inside as a disorganized mix. Which levels of organization can a dermoid cyst reach? Which level does a dermoid cyst never reach?

    Hint. A tooth forms like a small organ. Do the parts of a dermoid cyst work together, the way your heart and blood vessels do?

  4. A 2023 review of dermoid cyst studies reports teeth in 31% of cysts. Doctors at one hospital in New Delhi, India, found teeth in 10 of 223 dermoid cysts, about 4%. Why could two studies report such different numbers for teeth? Give two reasons.

    Hint. Think about how each study found and counted teeth, and which patients each study included.

Claim, evidence, reasoning

In the video, Raven says a dermoid cyst starts when an egg cell starts dividing on its own. In a 1990 study, Urvashi Surti’s team tested where dermoid cysts start. They compared chromosome markers in 89 dermoid cysts with the same markers in each patient’s healthy tissue. At these markers, each patient carried a heterozygous pair, two different versions. In 58 cysts, the pair had become homozygous, two matching versions. In 31 cysts, the pair stayed heterozygous. Mitosis, the division that copies body cells, keeps both chromosomes of a pair. Meiosis, the division on the way to an egg, separates the two chromosomes of each pair. Did dermoid cysts start from the patient’s own developing egg cells or from ordinary body cells? Make a claim, back it up with evidence, and explain your reasoning.

Hint. Ask which kind of cell division could turn a heterozygous pair into a homozygous pair.

Claim

Evidence

Reasoning

Going further: why a body plan needs both parents

  1. In the video, Raven says an egg that starts dividing on its own is how some species reproduce, but not mammals. Coquita the crocodile laid an egg holding a fully formed baby with no father’s DNA. Mouse embryos made only from a mother’s chromosomes don’t survive past day 10 of pregnancy. Raven says father DNA brings “the organization part.” Scientists call the reason genomic imprinting. In mammals like mice and people, some genes are switched on only in the copy from the father, and others only in the copy from the mother, according to a review by Denise Barlow and Marisa Bartolomei. Why does a mammal body plan need DNA from both parents? Use genomic imprinting in your answer.

    Hint. A mother’s chromosomes carry the same genes as a father’s. Think about which copies are switched on.

Exit ticket

A dermoid cyst can hold tissues from all three germ layers. What does a dermoid cyst show about how many kinds of cells one cell can make? And why is a dermoid cyst still not a body?

Hint. For the first part, think about how many kinds of tissue one cyst can hold. For the second part, think about levels of organization.

Sources