07-genetic-disorders

07-genetic-disorders - This lesson will increase your...

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Unformatted text preview: This lesson will increase your knowledge of concepts covered in the following TEKS for biology: 3.c – Evaluate impact of research on scientific thought, society, and the environment 3.e – Evaluate models according to their adequacy in representing biological objects or events 6.c – Identify and illustrate how changes in DNA cause mutations and evaluate the significance of these changes 6.e – Compare the processes of mitosis and meiosis and their significance to sexual and asexual reproduction Previous Lesson Individuality and Cloning Question: What is the difference between mitosis and meiosis? Mitosis is a process producing body cells whereas meiosis is a process producing gametes Daughter cells produced by mitosis are 2n (diploid) whereas daughter cells produced by meiosis are n (haploid) Question: From a scientific standpoint, what is the significance of Dolly? Dolly showed cloning of mammals was possible •Scientists can take DNA from an adult cell and re-start the reading of the DNA, as if it was DNA in a fertilized egg •DNA can then direct the synthesis of proteins to produce an embryo and eventually a clone of the adult Question: From a chromosomal standpoint, what is wrong with the idea of using a sperm and an egg from super athletes to try to have a super athlete child? Random assortment of chromosomes causes the sperm and egg to have different chromosome combinations Meiosis I Meiosis II Fig. 23.6 Based on: Mader, S., Inquiry Into Life, McGraw-Hill The child may not get the “athletic” chromosomes The chromosomes can line up 223 or 10 million different ways in meiosis I Each person can produce 10 million different types of gametes Question: Why not try to clone the super athlete? Cloning of Humans • Cloning results in higher rates of miscarriage and death…using today’s technology • Although the clone would be genetically identical, the environment that produced the super athlete would be different…same nature, different nurture Today’s Lesson Today’s Genetic Disorders and Genetic Gene Therapy Gene Overview of Lesson • Genetic diseases – Chromosomal – Single gene • Genetic Testing • Gene Therapy Chromosomal Diseases Chromosomal • Gametes have abnormal Gametes chromosome numbers and mutations mutations • Offspring inherit extra Offspring chromosome or are missing a chromosome chromosome • Caused by problems with Caused meiosis meiosis Nondisjunction of chromosomes during meiosis Based on: Brooks/Cole – Thomson Learning Characteristics of a child with Down Syndrome Down -wide, rounded face -mentally retarded -enlarged tongue -enlarged Normal female karyotype with 46 chromosomes Based on: Mader, S., Inquiry Into Life, McGraw-Hill -equal length fingers -webbed neck Down syndrome karyotype with an extra chromosome 21 Amniocentesis •Used on pregnant women over 35 years of age •Performed during weeks 15-17 of pregnancy •A needle is inserted into the amniotic sac •Amniotic fluid with fetal cells is removed •A karyotype of the fetal chromosomes is prepared Risk of Having Child with Down Syndrome versus Risk of Miscarriage due to Amniocentesis Risk of Down Syndrome Risk of Miscarriage Overview of Lesson • Genetic diseases – Chromosomal – Single gene • Genetic Testing • Gene Therapy Important Points about Inheritance Important •Genes have different forms, called Genes alleles alleles •Each trait is controlled by effects of Each two alleles two •Some alleles are dominant/recessive Some and other alleles are co-dominant and •Allele for Widow’s Peak Allele is dominant is •A person with WW or Ww person will have Widow’s Peak will •Allele for Straight Hairline Allele is recessive is •A person with ww will have person a Straight Hairline Straight http://images.google.com/ Genotype vs. Phenotype Genotype •Genotype refers to the alleles •Phenotype refers to the appearance Example: Genotype - Phenotype WW - person has a widow’s peak Ww - person has a widow’s peak ww - person has a straight hair line Genetics Problem Genetics • A woman (Ww) with a widow’s woman peak has children with a man (ww) with a straight hairline (ww) • What is the chance that the child What will have a widow’s peak? will Alleles W = Widow’s peak w = Straight Genotypes-Phenotypes WW - Widow’s peak Ww - Widow’s peak ww - Straight Female Ww eggs W w w Ww ww w Ww ww Male ww Offspring sperm Each child would have a 50% chance of having a widow’s peak Question: Why would a person Question: with a genotype of Ww, produce gametes with W and gametes with w? gametes Gametes Huntington Disease Huntington Person gradually loses Person psychomotor control in adulthood adulthood Caused by dominant Caused allele allele Genetics Problem • A woman (hh) with normal nerve physiology has a child with a man (Hh) who will develop Huntington Disease • What is the chance that the child will have Huntington Disease? Alleles H = Huntington h = Normal Genotypes-Phenotypes HH - Huntington Hh - Huntington hh - normal Female hh eggs Male Hh Offspring sperm Each child would have a __% chance of having Huntington Disease Alleles H = Huntington h = Normal Genotypes-Phenotypes HH - Huntington Hh - Huntington hh - normal Female hh eggs h h Male Hh H Hh Hh h hh hh Offspring sperm Each child would have a 50% chance of having Huntington Disease Cystic Fibrosis Cystic Mucus in bronchi is thick, Mucus interfering with lung function interfering Caused by a recessive allele Genetics Problem • A woman (Nn) with normal lung physiology has a child with a man (Nn) who has normal lung physiology (both are carriers of allele) • What is the chance that the child will have Cystic Fibrosis? Alleles N = Normal n = Cystic Fibrosis Genotypes-Phenotypes NN - Normal Nn - Normal nn - Cystic Fibrosis Female Nn eggs Male Nn Offspring sperm Each child would have a __% chance of having Cystic Fibrosis Alleles N = Normal n = Cystic Fibrosis Genotypes-Phenotypes NN - Normal Nn - Normal nn - Cystic Fibrosis Female Nn eggs N n N NN Nn n Nn nn Male Nn Offspring sperm Each child would have a 25% chance of having Cystic Fibrosis Sickle Cell Disease- recessive allele •Red blood cells are sickle shaped, issues with circulation causing anemia and pain Based on: Harvard Family Health Guide, 1999 Genetics Problem Genetics • A woman (Nn) with sickle woman cell trait has a child with a man (NN) who has normal red cells. normal • What is the chance that What the child will have Sickle Cell Trait? Cell Alleles N = Normal n = Sickle Cell Genotypes-Phenotypes NN - Normal Nn - Sickle Cell Trait nn - Sickle Cell Anemia Female Nn eggs Male NN Offspring sperm Each child would have a __% chance of having Sickle Cell Trait Alleles N = Normal n = Sickle Cell Genotypes-Phenotypes NN - Normal Nn - Sickle Cell Trait nn - Sickle Cell Anemia Female Nn eggs N n N NN Nn N NN Nn Male NN Offspring sperm Each child would have a 50% chance of having Sickle Cell trait Overview of Lesson • Genetic diseases – Chromosomal – Single gene • Genetic Testing • Gene Therapy Genetics & Human Diseases Genetics • About 4,000 human diseases are thought About to be inherited to • Scientists are making good progress Scientists figuring out where genes are located on chromosomes and in understanding how the mutations in genes cause disease the Genetic map of chromosome 17 Based on: Mader, S., Inquiry Into Life, McGraw-Hill Genetic Testing Genetic • Now have DNA tests for 30 - 40 Now diseases diseases – Cystic fibrosis, some forms of Cystic breast cancer, fragile X syndrome, Huntington disease, Duchenne muscular dystrophy muscular • Tests are up to 99% accurate • Tests can be run on embryos Tests created by in-vitro fertilization prior to implantation to Future of Genetic Testing Future When will we have tests for 1000s of genetic diseases in human or what project must be completed for scientists to understand the DNA-protein relationships that cause many human diseases? human Answer Issues about Genetic Testing Issues • What if the news is bad? Should the fetus be aborted What or allowed to live with a “cruel” disease? or • Should insurance coverage provide care for a child Should having a genetic disease that was diagnosed before birth? birth? • Should blood relatives be warned? • Should our genetics be part of our records? • Should employers be allowed to consider genetically Should based diseases in hiring employees? based • Will eugenics (manipulation of the hereditary qualities Will of a race) be practiced? of Overview of Lesson • Genetic diseases – Chromosomal – Single gene • Genetic Testing • Gene Therapy Gene Therapy Gene • Gene therapy is lagging behind genetic Gene testing testing – For example, gene for cystic fibrosis was For identified in 1989 – Scientists have been testing ways to insert Scientists copies of the normal gene into cells of the respiratory tract respiratory • It is difficult to get the gene inserted into It the tissue so that it can take over control of protein synthesis of Steps in Gene Therapy In Utero Approved gene-therapy trials Map shows 2004 Stats •In 2008 938 clinical trials for gene therapy ongoing in USA •In 2008 56 new trials were approved in USA Gene therapy trials are now underway around the world. When will the results be considered part of world knowledge? world Next Class Exam I (Lessons & Labs) Genetic tests for 1000s of genetic diseases will be available after the Proteome Project is completed…or after scientists figure out which proteins go with which genes… probably in 10-20 years. Back Scientific Methodology Scientific Observation World knowledge in scientific journals Hypotheses Publication Rejection Tests of hypotheses Peer review Results Submission of paper to scientific journal Back Meiosis - formation of gametes in gonads Meiosis Back Based on: Mader, S., Inquiry Into Life, McGraw-Hill ...
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