Biology

Standard IV, Objective 2, 3

Title: Find a Gene

Description: Students will use a model in the form of a jigsaw puzzle and corresponding pedigree to learn how genes are located. They will then use another pedigree and a more realistic model using chromosomes and gene pairs to locate another gene.

Time Needed: 50 to 90 minutes, depending on how the introductory reading is addressed.

Materials: Color copies of the jigsaw puzzle (one puzzle per pair of students is ideal) , the newspaper article (below) and the student sheet. The jigsaw may be expanded to a larger size for the students.

Procedures:

  1. Read the introduction with the students and have students read the newspaper

article “Five mental disorders share genetic links, huge study says”

2. Be sure to ask to students to try and answer the question: How do scientists use

DNA research to find out what genes cause specific traits?

  1. Discuss the student answers and then ask them to solve the puzzle. Make sure everyone understands how the puzzle is solved before moving on. A simple way to explain the solution is that every person on the pedigree that has the disorder, also has that gene. You may have to explain that since the first person has all red and has the disorder, the “gene” for the disorder must be red. Remind them to look at the pedigrees.
  2. The correct answer is: #36.
  3. Ask students to try the next “puzzle” using models of chromosome and their named genes. Explain DNA has many more base pairs than is pictured and that scientists know the entire human genome.

Reading:

Five mental disorders share genetic links, huge study says

By Lauran Neergaard

| The Associated Press

First Published Feb 27 2013 07:54 pm • Last Updated Feb 27 2013 10:21 pm

Washington • The largest genetic study of mental illnesses to date finds five major disorders may not look much alike but they share some gene-based risks. The surprising discovery comes in the quest to unravel what causes psychiatric disorders and how to better diagnose and treat them.

The disorders — autism, attention deficit-hyperactivity disorder or ADHD, bipolar disorder, major depressive disorder and schizophrenia — are considered distinct problems. But findings published online Wednesday suggest they’re related in some way.

"These disorders that we thought of as quite different may not have such sharp boundaries," said Dr. Jordan Smoller of Massachusetts General Hospital, one of the lead researchers for the international study appearing in The Lancet.

That has implications for learning how to diagnose mental illnesses with the same precision that physical illnesses are diagnosed, said Dr. Bruce Cuthbert of the National Institute on Mental Health, which funded the research.

Consider: Just because someone has chest pain doesn’t mean it’s a heart attack; doctors have a variety of tests to find out. But there’s no blood test for schizophrenia or other mental illnesses. Instead, doctors rely on symptoms agreed upon by experts. Learning the genetic underpinnings of mental illnesses is part of one day knowing if someone’s symptoms really are schizophrenia and not something a bit different.

"If we really want to diagnose and treat people effectively, we have to get to these more fine-grained understandings of what’s actually going wrong biologically," Cuthbert explained.

Added Mass General’s Smoller: "We are still in the early stages of understanding what are the causes of mental illnesses, so these are clues."

The Psychiatric Genomics Consortium, a collaboration of researchers in 19 countries, analyzed the genomes of more than 61,000 people, some with one of the five disorders and some without. They found four regions of the genetic code where variation was linked to all five disorders.

Of particular interest are disruptions in two specific genes that regulate the flow of calcium in brain cells, key to how neurons signal each other. That suggests that this change in a basic brain function could be one early pathway that leaves someone vulnerable to developing these disorders, depending on what else goes wrong.

For patients and their families, the research offers no immediate benefit. These disorders are thought to be caused by a complex mix of numerous genes and other risk factors that range from exposures in the womb to the experiences of daily life.

"There may be many paths to each of these illnesses," Smoller cautioned.

But the study offers a lead in the hunt for psychiatric treatments, said NIMH’s Cuthbert. Drugs that affect calcium channels in other parts of the body are used for such conditions as high blood pressure, and scientists could explore whether they’d be useful for psychiatric disorders as well.

The findings make sense, as there is some overlap in the symptoms of the different disorders, he said. People with schizophrenia can have some of the same social withdrawal that’s so characteristic of autism, for example. Nor is it uncommon for people to be affected by more than one psychiatric disorder.

Copyright 2013 The Salt Lake Tribune. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Student SheetName______

Period______

Title: Find a Gene

Introduction: Just like in the news story you just read, scientists are “finding” genes for many different human conditions on a regular basis. Often, the gene is for a disorder that affects people directly, like cystic fibrosis, or contributes to disease conditions like the article you just read. Scientists are rapidly unraveling the “code” of life found in DNA to find out what it says!

Materials: color print of the puzzle, copy of the news story

Procedures:

  1. Read the newspaper article “Five mental disorders share genetic links, huge study says”

Try and answer the question: How do scientists use DNA research to find out what genes

cause specific traits?

2. Use the jigsaw puzzle and pedigree of an imaginary trait to find out which “gene” or puzzle piece is found in the genome of every affected person. Remember that every person on the pedigree that has the disorder, also has that gene. So, since the first person has all red and has the disorder, the “gene” for the disorder must be red. Look at the pedigrees to see which piece all the affected individuals have in common.

3.Try the next “puzzle” using models of chromosome and their named genes. Which gene explains this condition?

4. Answer the analysis questions as you finish.

Part 1-Use this pedigree to find the whirling “gene”. The chart on the next page will help you name the gene.

Analysis:

  1. Which piece is found in every affected person?
  1. Is the trait recessive or dominant? How do you know?

3. How is this model different that a real situation?

Part 2

  1. Use the pedigree below to find the gene located on the chromosome pairs on the next page. Remember that each affect individual has the gene. The gene pairs are labeled by the chromosome number and the position of the gene.


Analysis:

  1. Which gene is responsible for this trait?
  1. Is it recessive or dominant? How do you know?
  1. What does this knowledge provide for a person who has the gene?
  1. If the gene caused a serious illness later in life, would you want to know if you carried it?