Gregor Mendel Genetics Pioneer PDF

Summary

This PDF document is a biography of Gregor Mendel, a scientist who made significant contributions to the field of genetics. His work with pea plants demonstrated the principles of inheritance. The book is designed for a secondary school audience.

Full Transcript

Gregor Mendel Genetics Pioneer To view a slides this book as ho View m w, pull down enu and the Screen...

Gregor Mendel Genetics Pioneer To view a slides this book as ho View m w, pull down enu and the Screen. sele To turn ct Full press th p e space ages, click th bar or e mous e. Lynn Van Gorp, M.S. Life Science Readers: Gregor Mendel: Genetics Pioneer Publishing Credits Editorial Director Creative Director Dona Herweck Rice Lee Aucoin Associate Editor Illustration Manager Joshua BishopRoby Timothy J. Bradley Editor-in-Chief Publisher Sharon Coan, M.S.Ed. Rachelle Cracchiolo, M.S.Ed. Science Contributor Sally Ride Science™ Science Consultants Thomas R. Ciccone, B.S., M.A.Ed., Chino Hills High School Dr. Ronald Edwards, DePaul University Teacher Created Materials Publishing 5301 Oceanus Drive Huntington Beach, CA 92649 http://www.tcmpub.com ISBN 978-0-7439-0598-5 © 2008 Teacher Created Materials Publishing  Table of Contents Gregor Johann Mendel..................................................... 4 A Teacher First, Then a Scientist...................................... 8 Genetics.......................................................................... 10 Mendel’s Laws of Heredity............................................. 14 Dominant and Recessive Genes...................................... 18 Mendel’s Research.......................................................... 22 Mendel’s Legacy............................................................. 24 Geneticist: Barbara McClintock..................................... 26 Appendices..................................................................... 28 Lab: Genetic Dominant/Recessive Trait Survey....................................................... 28 Glossary............................................................ 30 Index................................................................. 31 Sally Ride Science.............................................. 32 Image Credits.................................................... 32  Gregor Johann Mendel Johann Mendel (YOH-hahn MEN-dl) was born in 1822 into a poor farming family. He was born in the Austrian Empire, in a town that is now in the Czech (CHEK) Republic.  When Mendel grew up, he became a monk. He was also a botanist. A botanist is a scientist who studies plants. Mendel experimented with garden peas. People say he is the father of modern genetics because of his work. a view of Prague in the Czech Republic Czech Republic The Czech Republic is in Europe. It is in between Germany, Austria, and Poland. It is a small country. It is smaller than the state of South Carolina. Its capital city is Prague.  Mendel’s life was hard. He worked as a gardener when he was young, but he wanted a better life. It was almost impossible for poor people to get a good education. His parents helped pay for him to go to school. Then his father got hurt. After that, his two sisters helped Mendel. To continue his education, Mendel entered a monastery. It was a teaching monastery. It was a place for learning and scientific inquiry. There, Mendel was given the name Gregor (GREG-er). Monasteries such as this one in Greece have been centers of learning for centuries.  This is the monastery where Mendel lived. Monasteries There are monasteries all over the world. Monks and nuns live in them. They spend time praying and meditating there. The monks of Mendel’s monastery belonged to the Augustinian (aw-guhs-TIN-ee-in) order. Many well-known scientists lived in monasteries. People throughout time have often gone to monasteries to learn. Some do research and teach there. Monasteries also often give shelter to travelers and to the poor.  A Teacher First, Then a Scientist Mendel lived at the monastery. He became a priest when he was 25 years old. He got up every morning at six. He went straight to the library to study. He studied many sciences. He also taught Latin, Greek, and math to other students. He took a test to become an official teacher, but he did not pass it. So, he went to the University of Vienna to get his teaching diploma. Mendel is in the back He studied for two years. row of this group of Mendel was very sick when he took his monks and teachers from 1865. tests. Once again, he did not pass them. He decided to withdraw from the school. But even though he did not pass, he had learned valuable research skills. Test Anxiety When Mendel went to take his tests, he became ill. It is thought that he had test anxiety. He was so scared of taking the tests, he couldn’t even take them. Many people have test anxiety.  the University of Vienna Mendel couldn’t teach any longer. He had to do something else for work. At the university, he liked the work of a biologist there named Frank Unger. Biologists study the science of life and living things. Unger had a different view of inheritance. He looked at nature. He saw similarities and differences in the way animals and plants grew. Mendel had seen the same things when he was working on the family farm.  Genetics Reproduction is the process by which offspring are created. Each species reproduces its own kind. In other words, people make people. Dogs make dogs. Trees make trees. Reproduction is needed for a species to survive. When living things reproduce, they pass their genetic material to their offspring. This material is what makes a living thing what it is. It is found in the cells of living things. In the center of cells are chromosomes. Chromosomes are made of genes. In a human being, there are 23 pairs of chromosomes in each cell. Each chromosome holds thousands of genes. Traits pass from parent to offspring by way of these genes. People get their genes from both their birth parents. A person’s body follows the instructions given by the genes. These instructions tell the body everything, from what the person’s eye color should be to how big his or her feet should grow. People get their hair color, among other things, from their birth parents. 10 The same is true for other animals DNA and plants. The parent passes its traits to A baby’s first cell has a code in the offspring, whether the offspring is a it. The code has the instructions cow, monkey, pineapple, or elm tree. needed to make that baby. That first cell has little bits inside called chromosomes. Half these chromosomes come from the mother’s egg cell. Half come from the father’s sperm cell. The major part of all chromosomes is called DNA. DNA carries a person’s genetic information or code. Genes Genes determine the color of animals’ coats. Many genes interact to make the color. That’s why there are so many different color patterns in cats, dogs, and other animals. Chromosomes are so small that they can only be seen when they bunch together like this. 11 Mendel Studies Garden Peas Mendel’s father bred fruit trees. Mendel helped his father when he was young. That interest stayed with him. He wasn’t allowed to teach biology. But he could do research. It was not possible for Mendel to study fruit trees. So he studied other plants. He decided to research the common pea. He grew them in his garden. They were easy to raise. They had a short breeding time. Breeding is another word for reproduction. Best of all, the peas could be cross-pollinated. That means that one variety could be bred with another. Mendel bought seeds from people who lived in the area. Peas were a popular vegetable at that time. Many types were available. Mendel is said to have started with 34 different varieties of pea plants. Over time, he grew and tested at least 28,000 pea plants in his gardens. Interesting to See An illustration from the Album Benary (1876–1893) shows some of the characteristics of pea plants that Mendel studied. 12 Eugenics Many people oversimplified Mendel’s findings. They thought it would be easy to change people’s traits. Many countries wanted to improve the majority race that lived in them. They thought they could breed out traits they didn’t like. This is called eugenics (yoo-JEN-iks). Nazi Germany killed more than 200,000 people with disabilities. Some of these people were in mental institutions. Others had birth defects. In the end, it didn’t work. Genetics is very complicated. It cannot be controlled so easily. 13 Mendel’s Laws of Heredity Before Mendel, many people believed in the theory of blending. They thought offspring would have traits somewhere in between those of their parents. So, if a mother had blue eyes and a father had green eyes, their children would have blue-green eyes. This theory did not explain variations. It also could not explain the differences that occur a gene between species. Mendel crossbred, or mixed, thousands of pea plants. This allowed him to make predictions. These are now called Mendel’s Laws of Heredity. They explain how traits are passed from generation to generation. Peas and People Mendel studied garden peas. Scientists began to see that the concepts he described could be seen in people, too. This is a chromosome that contains DNA strands on which genes are arranged. 14 Eye Color Eye color is a physical trait. Some parents like to guess what their baby’s eye color will be. Eye color is partly determined by the amount of something called melanin. It is in the iris of the eye. Brown eyes have a lot of melanin. Blue eyes have very little. Genes control the amount of melanin. Most of the world’s people have dark eyes, ranging from brown to nearly black. Blue eyes only occur when neither parent gives the baby a brown gene. 15 Individual traits are inherited in expected or predictable ways. A genetic trait is called a genotype (JEE-nuh-tipe). A phenotype (FEE-nuh-type) is a trait you can see. It is the result of the interaction between a genotype and the environment. Examples include shape, size, and color. Mendel found that some traits show up in offspring without any The traits of the pea plant that blending. He looked at seven pairs of this pod comes from include a seed traits to compare them. Each trait tall stem, flowers on top, round had two phenotypes, or two differences he seeds, green seed color and coat, and a puffed green pod. could see. They were as follows: stem length—tall or short flower position—top or side More Alike Than Different seed shape—round or wrinkled Nearly 100 percent of each seed color—green or yellow person’s DNA is exactly the same flower color—purple or white as other people’s DNA! Only.1 percent is different. This small pod shape—puffed or pinched difference is why features such as pod color—green or yellow eye and hair color vary. It’s also why some people get sick and some have different reactions to medicine. Otherwise, we are very much the same. 16 Traits Mendel Compared Character Dominant Recessive Trait Trait stem length tall short flower position top side seed shape round wrinkled seed color yellow green flower color purple white pod shape puffed pinched pod color green yellow 17 Dominant and Recessive Genes Mendel discovered dominant and recessive genes. He noted the traits of each plant’s parents. He controlled how the plants were fertilized. He moved the pollen of the flower on one plant to the flower on another plant. For every trait, each parent passes one gene to its child. The child then has two genes. The genes interact with each other. The mix makes the child’s trait. There are two versions for each gene. The different versions are called alleles (uh-LEELS). There is one allele for attached earlobes. There is another allele for unattached earlobes. Sometimes the child gets two of the same allele. Sometimes the child gets two different ones. If the alleles are different, then one is dominant. The other is recessive. Dominant alleles only need one allele to be seen. Recessive alleles need two to be seen. A recesive gene will only be seen if both parents pass it on. An example is pod color in pea plants. The green-pod allele is dominant. Peas need only one green-pod allele to be green. The yellow-pod allele is recessive. The plant needs two yellow-pod alleles to be yellow. Orchid farmers often harvest pollen from one plant to breed it with another. 18 First Generation Yellow (yy) (Yy) (Yy) (Yy) (Yy) Allele Colors Green (YY) These bean pods have different- Second Generation color gene alleles. One pod color allele is green. The other is yellow. Green is the dominant Green (Yy) color. (YY) (Yy) Green (Yy) (Yy) (yy) This chart shows the possible allele combinations in two generations of pea pods. You can tell that there are The green dominant allele is shown with different alleles for hair color. a capital Y. The yellow recessive allele is These three children have shown with a lowercase y. The pod will be different hair-color alleles. We yellow only when it has two recessive alleles. know that because they have blond, red, and brown hair. 19 A human example of Mendel’s law can be seen in tongue rolling. The ability to roll one’s tongue is a dominant trait. Both parents have two genes that relate to tongue rolling. They got them from their parents. They can have either two dominant genes or two recessive genes. Or they can have one of each. They each pass one of their genes to their child. If a 20 parent has two dominant genes, they will have to pass down a dominant gene. If they have two recessive genes, they will pass down a recessive gene. If they have one of each, though, they might pass down either one. There’s no way of telling. If a child receives one of each gene, the child will be able to roll Color Blindness his or her tongue. The only way the Color blindness is a child won’t be able to roll it is if he genetic condition. People or she receives two recessive genes. who have it cannot see certain colors. There is no Dominant and Recessive Traits cure for it. About one out of 12 men is color-blind. About Dominant Recessive Traits Traits one out of 200 women is. eye color brown gray, green, Red/green color hazel, blue blindness is the most hair dark hair blond, light common type of color non-red red blindness. Someone with curly straight normal color vision will see facial dimples no dimples a 74 in the dot pattern above. features freckles no freckles Someone with red/green Remember: Both parents need to pass the recessive trait color blindness will see a 21 in order to inherit it. Do you have any recessive traits? in the pattern or no number at all. Tongue-rolling is a dominant trait. 21 Mendel’s Research Mendel worked very hard. He experimented with thousands of plants. He believed that his experiments would not work if he did not study enough plants. He thought his results might happen by chance, not science. He experimented in his garden for eight years. Mendel went to a meeting of scientists in 1865. He reported the results of his research. The scientists were polite. But they did not seem to understand the importance of his findings. His research was so different from other work being done at the time. There was very little reaction to his work. No one seemed to notice it. The next year, his report was published. Still, no one seemed to notice. Unfortunately, Mendel had few opportunities to share his work. It took a long time for people to find out about new research. There were no computers or Internet back then. If there were, maybe Mendel would have been recognized for his work before his death. Perhaps he would have been able to see how important his work would become. In fact, it provided the base for genetic research in the 20th century. This plant was the result of an experiment that crossed yellow wrinkled peas (top left) with green round peas (top right). 22 Rosalind Franklin (1920–1958) Another scientist who died before people recognized her work was Rosalind Franklin. She produced the first clear photograph of DNA. Sadly, she died of cancer in 1958. She was only 37 years old. Two other scientists used her photograph as part of their own research. In 1962, they were awarded the Nobel Prize for their work in mapping the structure of DNA. Franklin was not mentioned. However, the scientists later acknowledged Franklin’s work and its importance to their own. Today the world is well aware of Franklin and the contribution she made to genetics. Franklin’s photograph of DNA 23 Mendel’s Legacy Mendel died in 1884 at the age of 62. Few people were aware of his work until the early 1900s. That is when scientists began to understand and think about what he had done. More than 50 years after Mendel shared his research, another scientist named Hugo De Vries did similar work. Most of the results were similar. He came up with the idea of gene mutation. He thought a gene could change and make an instant change in the offspring. He said a mutation would show a change in a single generation. It wouldn’t wait until the second generation. He published a book about his theory. It was very controversial. People had strong opinions about his theory. 24 Dog Chromosomes Since then, other scientists have Dogs have more chromosomes studied pea plants. Some of their than you do! Dogs have 78 findings back up Mendel’s work. chromosomes. You have only Some disagree with Mendel’s findings. 46. Luckily, the number of chromosomes does not relate to Scientists today keep studying genes how advanced an organism is. to figure them out. There are still Dogs have more chromosomes, many questions to answer in the study but humans have more coding of genes. genes than any other species. Mendel’s Microscope Scientists knew they needed to Hugo De Vries did similar research to that of Mendel. understand more about how organisms reproduced. They needed to see detailed images of the parts of a cell. So, they needed to use a microscope. Mendel had used a microscope, but it was not powerful enough. He couldn’t see the chromosomes, or the parts of a cell that contain the genetic material. 25 Geneticist: Barbara McClintock Cold Spring Harbor Laboratory Jumping Genes Barbara McClintock never gave up. She spent most of her career growing corn to study genetics. For years, no one believed her conclusions. But she kept going. Her most surprising discovery was a very special gene that can swap places with other genes. Finally, at the age of 81, she won the 1983 Nobel Prize in Medicine! McClintock had a garden near her laboratory. She planted different kinds of corn so she could breed them and make new types. Some of those plants came from Central and South America, where she loved to travel. She also loved being a teacher. She taught until she died at the age of 90. 26 Being There Someone once said it could take McClintock a whole afternoon to answer a person’s question. Then, after talking for hours, she would say, “We’d better stop now—you look tired!” In Her Words “It might seem unfair to reward a person for having so much pleasure over the years.” McClintock had to sort through many ears of corn. 27 Lab: Genetic Dominant/Recessive In this lab, you will survey your families and friends. You will find out how many of them display certain dominant or recessive traits. The trait pairs you will survey are the following: free earlobes attached earlobes can roll tongue in a U shape can’t roll tongue in a U shape no widow’s peak widow’s peak dark brown eyes grey, green, or blue eyes index finger shorter than ring finger ring finger shorter than index finger dark hair light hair non-red hair red hair curly hair straight hair Materials paper pencil computer with spreadsheet application and a printer (optional) Procedure 1 Prepare a genetic dominant/recessive trait survey form. Using each of the categories listed at the top of this page, make a chart. Leave space after each column to tally total numbers. Above the left-hand column, add the title Dominant Traits. Above the right-hand column, add the 28 title Recessive Traits. Trait Survey 2 2 Ask your family members and friends which traits they have. 3 Record their responses on your form. 4 Total the number of responses you tallied for each trait. 5 Create a bar graph to display your results. If 4 you have them, use a computer and printer to create your graph. 6 Summarize your results. Conclusion Dominant traits show up more often than recessive traits. Genetic traits show up in predictable patterns within families. Did you come to the same conclusion? 5 Extension Idea for Further Study Use genetics as a keyword to research genetic traits on the Internet. Share your most interesting findings by creating a poster. 29 Glossary allele—each part of a gene pair heredity—the complete set of inherited botanist—scientist who studies plant characteristics of an organism; the life passing on of genetic factors from one generation to the next bred—kept animals for the purpose of producing offspring in a controlled way inheritance—transmission of traits or qualities from parent to offspring chromosome—a rod-shaped structure in a cell that carries the genes that monastery—a building in which monks determine the characteristics an and sometimes nuns and priests live organism inherits from its parents. and worship crossbreed—to breed new plants or mutation—a change in a gene resulting animals from genetically different in a new trait or characteristic that can individuals be inherited, and that can be beneficial, neutral, or harmful in its effect cross-pollinated—having the pollen from one plant’s flower transferred to Nobel Prize—award given each year another’s flower, allowing the genetic for achievement in chemistry, literature, traits to mix in their offspring physics, physiology or medicine, economics, and world peace DNA—a twisted double strand that is the major part of chromosomes and offspring—the descendants of people, carries genetic information animals, and plants dominant trait—a trait that appears to phenotype—the visible characteristics mask or hide other traits of an organism, resulting from the interaction between its genes and the eugenics—science that attempts to environment improve the human race recessive trait—a trait that can be fertilize—to put a natural or chemical hidden in one generation and then substance on land in order to make appear in the next generation plants grow well reproduction—the act of living things to gene—a part of a cell’s DNA that produce offspring contains information in a pattern received by each living thing from its Theory of Blending—theory that certain parents, and which controls its physical traits show up in offspring as a blend of development, behavior, etc. their parents’ characteristics genetics—a branch of science dealing trait—a distinguishing characteristic with heredity and genetic variations genotype—the genetic makeup of an organism, as opposed to its visible characteristics 30 Index allele, 18–19 heredity, 14–15 Album Benary, 13 inheritance, 9–10, 16, 21 Augustinian order, 7 Mendel’s Laws of Heredity, botanist, 5 14–17 bred, 12, 14 monastery, 6–8 chromosome, 10–11, 14, 25 mutation, 24–25 color blindness, 21 McClintock, Barbara, 26–27 crossbreed, 14, 22 Nobel Prize, 23, 26 DNA, 11, 14, 16, 23 offspring, 10–11, 14, 16, 24 dominant allele, 18–19 phenotype, 16 dominant gene, 18–21 pollinate, 12 dominant trait, 17, 20–21, recessive allele, 18–19 28–29 recessive gene, 18–20 eugenics, 13 recessive trait, 17, 21, 28–29 fertilize, 18 Theory of Blending, 14, 16 Franklin, Rosalind, 23 trait, 13–28, 20–21, 28–29 gene, 10–11, 14–15, 24–27 Unger, Frank, 9 genotype, 16 31 Sally Ride Science Sally Ride Science™ is an innovative content company dedicated to fueling young people’s interests in science. Our publications and programs provide opportunities for students and teachers to explore the captivating world of science—from astrobiology to zoology. We bring science to life and show young people that science is creative, collaborative, fascinating, and fun. To learn more, visit www.SallyRideScience.com Image Credits Cover: Bettmann/CORBIS; p.3 Joanne Harris and Daniel Bubnich/Shutterstock; p.4 (top) Benjamin F. Haith/Shutterstock; p.4 Mary Evans Picture Library/Alamy; pp.4–5 Matt Purciel/Shutterstock; p.6 Razvan Stroie/Shutterstock; p.7 SPL/Photo Researchers, Inc.; p.8 (top) Vladimír Radosa/ Shutterstock; p.8 (left) Haverford College; p.8 (bottom) Paul Reid/Shutterstock; p.9 Hulton Archive/Getty Images; p.10 (top) Pixshots/Shutterstock; p.10 Photos.com; p.11 (left) Adrian T. Sumner/SPL/Photo Researchers, Inc.; p.11 (bottom) Claudia Steininger/Shutterstock; p.12 Tim Bradley; pp.12–13 Ievgeniia Tikhonova/Shutterstock; p.13 Joy M. Prescott/Shutterstock; p.13 (right) Albert Campbell/Shutterstock; p.14 (top) Photos.com; p.14 (right) ANDREW SYRED/SPL/Photo Researchers, Inc.; p.14 (bottom) sgame/Shutterstock; p.15 (left) CORBIS; p.15 (right) Philip Date/Shutterstock; p.15 (bottom) Liv friis-larsen/Shutterstock; p.16 Leonid Nishko/Shutterstock; p.17 Tim Bradley; p.18 (top) Photos.com; p.18 (bottom) Tim Bradley; p.19 (left) Tim Bradley; p.19 (top) Photos.com; p.19 (bottom) Kuzma/Shutterstock; p.20 Ole Graf/zefa/CORBIS; p.21 BrandX/Superstock; p.22 (top) Paul Cowan/Shutterstock; p.22 Mary Evans Picture Library/Alamy; p23 (back) Courtesy of Haverford College; p.23 (top) Scott Laumann; p.23 (bottom) Oregon State University Foundation; p.24 (top) David B. Fankhauser, Ph.D.; pp.24–25 Roger Viollet/Getty Images; p.25 (right) Courtesy of Philip Meneely; p.26 (top) USPS; p.26 (bottom) USDA; p.27 Cheryl A. Meyer/Shutterstock; p.27 (bottom) National Library of Medicine; p.28 (top) Valentin Mosichev/Shutterstock; pp.28–29 Nicolle Rager Fuller; p.32 Getty Images 32

Use Quizgecko on...
Browser
Browser