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Genetic Disorders — Reading Comprehension

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MS-LS3-2

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This comprehensive middle school reading passage introduces students to genetic disorders, focusing on both single gene and chromosome disorders. Students will learn about the mechanisms of inheritance using real-world examples such as cystic fibrosis, sickle cell disease, Huntington's disease, Down syndrome, Turner syndrome, and Klinefelter syndrome. The passage explains how Punnett squares are used to predict inheritance patterns and highlights the importance of genetic testing and counseling. Advances in gene therapy and the importance of understanding that genetic disorders are not the individual's fault are also discussed. Designed to align with NGSS MS-LS3-2, this resource integrates scientific vocabulary, cause-and-effect reasoning, and real-world applications. Audio integration enhances accessibility for diverse learners. This passage is ideal for middle school curricula aiming to build foundational genetics knowledge and scientific literacy.

CONTENT PREVIEW

dna-close-up — Genetic disorders occur when changes in genes or chromosomes lead to medical conditions.

Genetic disorders are health conditions caused by changes in a person's genes or chromosomes. Scientists study these disorders to understand why some people are affected and how they are passed from parents to children. Knowing about genetic disorders helps doctors develop treatments and support families. Some genetic disorders are common, and learning about them can help us understand how traits and health conditions are inherited.

How Genetic Disorders Are Inherited

Genes are segments of DNA that give instructions for how our bodies work. Each person has two copies of most genes, one from their mother and one from their father. Genetic disorders can be caused by mutations, or changes, in these genes. Some disorders are recessive, meaning both copies of a gene must have a mutation for the disorder to appear. For example, cystic fibrosis is a recessive disorder. If both parents are carriers (they have one normal gene and one mutated gene), there is a 25% chance their child will have the disorder. Other disorders, like Huntington's disease, are dominant, which means only one mutated gene is needed for the disorder to show up. Punnett squares help predict these inheritance patterns. Sickle cell disease is a special case called codominance, where both gene versions are partly expressed.

Chromosome Disorders and Real-World Examples

Some genetic disorders happen when people have extra or missing chromosomes. Down syndrome occurs when there is an extra copy of chromosome 21. This leads to developmental differences and health challenges. Turner syndrome affects females who have only one X chromosome instead of two. Klinefelter syndrome affects males who have an extra X chromosome. These chromosome disorders are not inherited directly like single-gene disorders. Instead, they happen because of random errors during cell division. Scientists can detect these changes using genetic testing.

Genetic Testing, Counseling, and Advances in Treatment

Genetic testing allows doctors to find out if a person has a genetic disorder or is a carrier. Genetic counseling helps families understand what test results mean and what choices they might have. New treatments, such as gene therapy, are being developed to fix or replace faulty genes. While not all genetic disorders can be cured, medical advances are making a big difference. It's important to remember that genetic disorders are not a person's fault—they are the result of changes in the DNA or chromosomes, which people cannot control.

Understanding genetic disorders connects to larger scientific principles, such as the role of DNA and the process of inheritance. As scientists learn more, they can help more people live healthier lives.

Interesting Fact: The Human Genome Project, finished in 2003, mapped all the genes in human DNA—about 20,000 to 25,000 genes!

What is a genetic disorder?

A health problem caused by changes in genes or chromosomesA disease caused by bacteriaA physical injuryA disorder from eating unhealthy food

Which of these is a single gene disorder?

Down syndromeCystic fibrosisTurner syndromeKlinefelter syndrome

What does a Punnett square help predict?

How genes will be inheritedWhat chromosomes look likeHow old a person isWhich therapy is best

What is the chance of a child having cystic fibrosis if both parents are carriers?

0%25%50%100%

What does 'recessive' mean in genetics?

Only one gene copy needs to be changedBoth gene copies must be changedGenes are not involvedIt only affects males

In the context of the passage, what is codominance?