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?

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 Dolly showed cloning of mammals was possible

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?

Fig Meiosis I Meiosis II Based on: Mader, S., Inquiry Into Life, McGraw-Hill Random assortment of chromosomes causes the sperm and egg to have different chromosome combinations

The chromosomes can line up 2 23 or 10 million different ways in meiosis I Each person can produce 10 million different types of gametes The child may not get the “athletic” chromosomes

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 Genetic Disorders and Gene Therapy Today’s Lesson Genetic Disorders and Gene Therapy

Overview of Lesson Genetic diseases –Chromosomal –Single gene Genetic Testing Gene Therapy

Chromosomal Diseases Gametes have abnormal chromosome numbers and mutationsGametes have abnormal chromosome numbers and mutations Offspring inherit extra chromosome or are missing a chromosomeOffspring inherit extra chromosome or are missing a chromosome Caused by problems with meiosisCaused by problems with meiosis

Based on: Brooks/Cole – Thomson Learning Nondisjunction of chromosomes during meiosis

Characteristics of a child with Down Syndrome -wide, rounded face -equal length fingers -mentally retarded -webbed neck -enlarged tongue Normal female karyotype with 46 chromosomes Down syndrome karyotype with an extra chromosome 21 Based on: Mader, S., Inquiry Into Life, McGraw-Hill

Used on pregnant women over 35 years of ageUsed on pregnant women over 35 years of age Performed during weeks of pregnancyPerformed during weeks of pregnancy A needle is inserted into the amniotic sacA needle is inserted into the amniotic sac Amniotic fluid with fetal cells is removedAmniotic fluid with fetal cells is removed A karyotype of the fetal chromosomes is preparedA karyotype of the fetal chromosomes is prepared Amniocentesis

Risk of Miscarriage Risk of Down Syndrome Risk of Having Child with Down Syndrome versus Risk of Miscarriage due to Amniocentesis

Overview of Lesson Genetic diseases –Chromosomal –Single gene Genetic Testing Gene Therapy

Important Points about Inheritance Genes have different forms, calledGenes have different forms, called alleles alleles Each trait is controlled by effects ofEach trait is controlled by effects of two alleles two alleles Some alleles are dominant/recessiveSome alleles are dominant/recessive and other alleles are co-dominant and other alleles are co-dominant

Allele for Widow’s PeakAllele for Widow’s Peak is dominant is dominant A person with WW or WwA person with WW or Ww will have Widow’s Peak will have Widow’s Peak Allele for Straight HairlineAllele for Straight Hairline is recessive is recessive A person with ww will haveA person with ww will have a Straight Hairline a Straight Hairline

Genotype vs. Phenotype Genotype refers to the allelesGenotype refers to the alleles Phenotype refers to the appearancePhenotype 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 A woman (Ww) with a widow’s peak has children with a man (ww) with a straight hairlineA woman (Ww) with a widow’s peak has children with a man (ww) with a straight hairline What is the chance that the child will have a widow’s peak?What is the chance that the child will have a widow’s peak?

w w W w ww Ww ww Offspring Ww Male ww Female Ww eggs sperm Alleles W = Widow’s peak w = Straight Genotypes-Phenotypes WW - Widow’s peak Ww - Widow’s peak ww - Straight Each child would have a 50% chance of having a widow’s peak

Question: Why would a person with a genotype of Ww, produce gametes with W and gametes with w? Gametes

Huntington Disease Person gradually loses psychomotor control in adulthood Caused by dominant 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?

Offspring Male Hh Female hh eggs sperm Alleles H = Huntington h = Normal Genotypes-Phenotypes HH - Huntington Hh - Huntington hh - normal Each child would have a __% chance of having Huntington Disease

H h h h Hh hh Offspring Hh Male Hh Female hh eggs sperm Alleles H = Huntington h = Normal Genotypes-Phenotypes HH - Huntington Hh - Huntington hh - normal Each child would have a 50% chance of having Huntington Disease

Cystic Fibrosis Mucus in bronchi is thick, interfering with lung function 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?

Offspring Male Nn Female Nn eggs sperm Genotypes-Phenotypes NN - Normal Nn - Normal nn - Cystic Fibrosis Alleles N = Normal n = Cystic Fibrosis Each child would have a __% chance of having Cystic Fibrosis

N n N n Nn nn Offspring NN Male Nn Female Nn eggs sperm Genotypes-Phenotypes NN - Normal Nn - Normal nn - Cystic Fibrosis Alleles N = Normal n = Cystic Fibrosis Each child would have a 25% chance of having Cystic Fibrosis

Based on: Harvard Family Health Guide, 1999 Sickle Cell Disease- recessive allele Red blood cells are sickle shaped, issues with circulation causing anemia and pain

Genetics Problem A woman (Nn) with sickle cell trait has a child with a man (NN) who has normal red cells.A woman (Nn) with sickle cell trait has a child with a man (NN) who has normal red cells. What is the chance that the child will have Sickle Cell Trait?What is the chance that the child will have Sickle Cell Trait?

Alleles N = Normal n = Sickle Cell Offspring Male NN Female Nn eggs sperm Genotypes-Phenotypes NN - Normal Nn - Sickle Cell Trait nn - Sickle Cell Anemia Each child would have a __% chance of having Sickle Cell Trait

Alleles N = Normal n = Sickle Cell N N N n Nn NN Nn Offspring NN Male NN Female Nn eggs sperm Genotypes-Phenotypes NN - Normal Nn - Sickle Cell Trait nn - Sickle Cell Anemia 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 About 4,000 human diseases are thought to be inheritedAbout 4,000 human diseases are thought to be inherited Scientists are making good progress figuring out where genes are located on chromosomes and in understanding how the mutations in genes cause diseaseScientists are making good progress figuring out where genes are located on chromosomes and in understanding how the mutations in genes cause disease

Genetic map of chromosome 17 Based on: Mader, S., Inquiry Into Life, McGraw-Hill

Genetic Testing Now have DNA tests for diseasesNow have DNA tests for diseases –Cystic fibrosis, some forms of breast cancer, fragile X syndrome, Huntington disease, Duchenne muscular dystrophy Tests are up to 99% accurateTests are up to 99% accurate Tests can be run on embryos created by in-vitro fertilization prior to implantationTests can be run on embryos created by in-vitro fertilization prior to implantation

Future of Genetic Testing 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? 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? Answer

Issues about Genetic Testing What if the news is bad? Should the fetus be aborted or allowed to live with a “cruel” disease?What if the news is bad? Should the fetus be aborted or allowed to live with a “cruel” disease? Should insurance coverage provide care for a child having a genetic disease that was diagnosed before birth?Should insurance coverage provide care for a child having a genetic disease that was diagnosed before birth? Should blood relatives be warned?Should blood relatives be warned? Should our genetics be part of our records?Should our genetics be part of our records? Should employers be allowed to consider genetically based diseases in hiring employees?Should employers be allowed to consider genetically based diseases in hiring employees? Will eugenics (manipulation of the hereditary qualities of a race) be practiced?Will eugenics (manipulation of the hereditary qualities of a race) be practiced?

Overview of Lesson Genetic diseases –Chromosomal –Single gene Genetic Testing Gene Therapy

Gene therapy is lagging behind genetic testingGene therapy is lagging behind genetic testing –For example, gene for cystic fibrosis was identified in 1989 –Scientists have been testing ways to insert copies of the normal gene into cells of the respiratory tract It is difficult to get the gene inserted into the tissue so that it can take over control of protein synthesisIt is difficult to get the gene inserted into the tissue so that it can take over control of protein synthesis

Steps in Gene Therapy In Utero

Gene therapy trials are now underway around the world. When will the results be considered part of world knowledge? world knowledgeworld knowledge Approved gene-therapy trials In clinical trials for gene therapy ongoing in USA In new trials were approved in USA Map shows 2004 Stats

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 years. Back

Scientific Methodology World knowledge in scientific journals Publication Rejection Peer review Submission of paper to scientific journal Observation Hypotheses Tests of hypotheses Results Back

Meiosis - formation of gametes in gonads Back Based on: Mader, S., Inquiry Into Life, McGraw-Hill