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Chapter 8 Objectives Identify five complex patterns of heredity.
Section 4 Complex Patterns of Heredity Chapter 8 Objectives Identify five complex patterns of heredity. Describe how mutations can cause genetic disorders. List several genetic disorders and describe their modes of inheritance Evaluate the benefits of genetic counseling.
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New Vocabulary Polygenic inheritance Incomplete dominance Codominance
Multiple alleles
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Complex Patterns of Inheritance
Patterns of Inheritance that are explained by Mendel’s rules and laws are often referred to as _______________... They involve _____ contrasting forms of a trait However, many inheritance patterns are more ___________ than those studied by Mendel simple 2 complex
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Your text discusses five types of complex inheritance…
______________ dominance _______________ ______________ alleles ________________ polygenic incomplete codominance multiple Sex-linked
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Polygenic Inheritance
Section 4 Complex Patterns of Heredity Chapter 8 Polygenic Inheritance When _____________ genes influence a trait, the trait is said to be a _________________ trait. The genes for a polygenic trait may be scattered along the ________ chromosome or located on _______________ chromosomes. Familiar examples of polygenic traits in humans include __________, ____________, and _______ color, _______ color, and ________ color several polygenic same different height weight eye skin hair
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When several genes control a trait, a great range of ________________ is seen in the phenotypes
For example, there is wide range of human ___________ and _____________ For human hair, eye, and skin __________, there is also a wide range in phenotypes from _______ to ___________ variation height weight color light dark
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curve minimum maximum maximum minimum value value
When graphed, polygenic traits usually show a ___________ ranging from the ______________ value to the _______________ value minimum maximum minimum value maximum value
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10 cm 4 cm or 16 cm maximum minimum value value
As shown in this graph for stem height, what height is the most common? Least common? 10 cm 4 cm or 16 cm minimum value maximum value
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Chapter 8 Incomplete Dominance
Section 4 Complex Patterns of Heredity Chapter 8 Incomplete Dominance This inheritance pattern causes the phenotype of a _______________ individual to be _________________ between the two homozygotes. For example, when a snapdragon with red flowers is crossed with a snapdragon with white flowers, a snapdragon with ______ flowers is produced. heterozygous intermediate pink
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R R’ R R’ RR RR’ RR’ R’R’ 1RR : 2 RR’ : 1 R’R’
Use the following genotypes to complete and analyze the following cross… RR = Red R’R’= White RR’ = Pink Genotype Ratio? Phenotype Ratio? R R’ R RR RR’ R’ RR’ R’R’ 1RR : 2 RR’ : 1 R’R’ 1 Red : 2 Pink : 1 White
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In humans, hair ___________ is governed by incomplete dominance
What would be the intermediate result produced by a cross of one parent with straight hair and another with curly hair? texture Wavy hair
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Codominance Codominant alleles cause the phenotypes of ________ homozygotes to be expressed _____________ Codominance controls the __________ color of chickens BB = __________________ WW = _________________ BW = __________________ both equally feather Black feathers White feathers Black and white (checkered)
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Chapter 8 Multiple Alleles
Section 4 Complex Patterns of Heredity Chapter 8 Multiple Alleles Genes with _______ or more alleles are said to have multiple alleles. For example, in the human population, blood types are determined by three alleles…._____, _____, and ______ The superscripts A and B refer to _______________ on the surface of red blood cells These carbohydrates are also called ___________ molecules or ______________ three IA IB i carbohydrates surface antigens
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Even for traits controlled by genes with multiple alleles, an individual can have only _____ of the possible alleles for that gene. IA and IB are dominant to _____ IA and IB are ___________________ to each other two i codominant
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Blood Type A surface molecules are ______________ Caused by two allele combinations… ________ square IAIA IAi
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Blood Type B surface molecules are ______________ Caused by two allele combinations… ________ rounded IBIB IBi
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Blood Type AB Red blood cells have _________ A and B surface molecules because they are _________________ Caused by one allele combination… ________ both codominant IAIB
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Blood Type O Red blood cells have ____ surface molecules Caused by one allele combination… ________ no ii
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transfusion immune death no added donor both receive acceptor
It is important to determine blood types before a patient receives a blood _______________ because incompatible surface molecules trigger the body’s ______________ system and can cause ___________ Since blood type O has ______ surface molecules, it can be _______ to any ABO blood type It is called a universal _____________ Since blood type AB has ________ surface molecules, it can ______________ any ABO blood type It is called a universal ______________ transfusion immune death no added donor both receive acceptor
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The Rh factor is another surface molecule on red blood cells...
If you are Rh positive, you ___________ this extra surface molecule If you are Rh negative, you do _____ have this extra surface molecule Negative individuals may only receive _________ versions of A, B, AB, and O blood types have not negative
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A child is produced with type O blood
A child is produced with type O blood. Is it possible for the mother to have type AB blood and the father to have type O blood? Let’s find out with a Punnett square! IA IB i IAi IBi i IAi IBi Blood tests can determine who are _____________ parents, but _____ tests are needed to determine actual parenthood. possible DNA
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Chapter 8 Characters Influenced by the Environment
Section 4 Complex Patterns of Heredity Chapter 8 Characters Influenced by the Environment An individual’s phenotype often depends on conditions in the __________________. Because identical twins have identical __________, they are often used to study environmental influences. Since they are genetically identical, any differences between them are attributed to _________________ influences. environment genes environmental
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white brown Nutrition Example 1
Temperature affects the color fur of an arctic fox ____________ or ____________ Example 2 ________________ affects human height and weight Malnutritioned individuals will not reach the height or weight determined by their genes white brown Nutrition
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Your text also discusses several genetic disorders…
Most genetic disorders are the result of a faulty ________________ and are caused by the inheritance of _____ recessive alleles proteins two
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Chapter 8 Cystic Fibrosis (CF) _____________ genetic disorder
Section 4 Complex Patterns of Heredity Chapter 8 Cystic Fibrosis (CF) _____________ genetic disorder Caused by a defective gene that normally produces a protein responsible for moving ____________ ions into and out of cells This causes the formation and accumulation of a thick __________ in the _______, _________, intestines, and _____________ recessive chloride mucus lungs liver pancreas
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Section 4 Complex Patterns of Heredity
Chapter 8 Cystic fibrosis is the most common ____________ hereditary disorder among Caucasians. One in ____ Caucasian individuals has at least ________ copy of the defective gene These individuals don’t have cystic fibrosis but they are considered ________________ About one in _________ Caucasians born in the United States inherits cystic fibrosis fatal 25 one carriers 2500
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Tay - Sachs Disease Caused by recessive alleles that produce a defective ___________ enzyme. Common in ___________ populations In early childhood, the ___________ ___________ system begins to break down, eventually leading to ____________ brain Jewish nervous system death
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Chapter 8 Sickle Cell Anemia
Section 4 Complex Patterns of Heredity Chapter 8 Sickle Cell Anemia Sickle cell anemia is also caused by inheriting ______ recessive alleles. These alleles produce a defective form of the protein ____________________, which causes many red blood cells to bend into a _____________ shape, affecting their ability to carry _______________ two hemoglobin sickle oxygen
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damage Tissue _______________ may result if certain cells are not receiving enough oxygen The sickle cells may also ______________ small vessels and _____________ easily ______________________ individuals actually have _________ normal red blood cells and sickle cells Due to this occurrence, many texts actually list this disease as being controlled by ____________ inheritance instead of simple recessive block rupture Heterozygous both codominant
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Heterozygous individuals are protected from the affects of a parasite that invades red blood cells and causes ____________________ The sickle shape causes resistance to the ________________ Sickle cell alleles are most common in ____________ Americans One in ______ African Americans are heterozygous for the disease One in ______ African Americans has sickle cell anemia malaria parasite African 12 500
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Section 4 Complex Patterns of Heredity
Chapter 8 Hemophilia Another recessive genetic disorder is hemophilia, a condition that impairs the blood’s ability to ________. Hemophilia is a _____________ trait because the genes that control blood clotting are found on the _____ chromosome. How many recessive alleles must a female inherit to have hemophilia? And males? clot sex-linked X 2 1
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Chapter 8 dominant autosome 1 30s 40s passed muscle death
Section 4 Complex Patterns of Heredity Chapter 8 Huntington’s Disease (HD) Huntington’s disease is a genetic disorder caused by a ____________ allele located on an ____________. How many alleles does an individual need to inherit to have HD? The first symptoms of HD— mild forgetfulness, irritability, and slurred speech —appear in victims in their _________ or __________ Many people have had children by this age, so HD is often ____________ on in families. In time, HD causes loss of ___________ control, uncontrollable physical spasms, severe mental illness, and eventually ____________. dominant autosome 1 30s 40s passed muscle death
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Review Question! How are these inherited diseases different from the causes of an inherited disease like Down syndrome? Down syndrome is due to a nondisjunction
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Treating Genetic Disorders
Section 4 Complex Patterns of Heredity Chapter 8 Treating Genetic Disorders Most genetic disorders cannot be cured, although progress is being made. A person with a family history of genetic disorders may wish to undergo genetic _______________ and _____________ before becoming a ____________. In some cases, a genetic disorder can be ___________ if it is diagnosed early enough. testing counseling parent treated
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Example 1 Phenylketonuria or _______ is treatable genetic disorder caused by a faulty enzyme that is incapable of breaking down the amino acid ___________________. Phenylalanine is found in food products like ________ and ________________ sweeteners If newborns with PKU eat these food products, they will develop irreversible symptoms of _______________ ________________ PKU phenylalanine milk artificial mental retardation
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After birth, infants are given a PKU ______.
If positive for PKU, what do you think would be an easy and appropriate form of treatment for the infant? Example 2 …there also tests to detect ______...if positive, couples may choose to __________ from having children test Eliminating phenylalanine from their diet HD refrain
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Section 4 Complex Patterns of Heredity
Chapter 8 Gene Therapy Gene technology may soon allow scientists to correct certain recessive genetic disorders by ____________ defective genes with copies of ___________ ones, an approach called gene therapy. The essential first step in gene therapy is to _____________ a copy of the gene. Example: the cystic fibrosis gene was isolated in ________ replacing healthy isolate 1989
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Scientists then make use of ________________ DNA technology to insert the healthy gene into defective tissues __________________ enzymes are used to cut out needed portions of DNA and to insert them into a vector like a ____________ The virus then inserts the _____________ DNA into defective cells recombinant Restriction virus virus correct
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cold Scientists have used the ________ virus to successfully correct defective lung tissues in a _________ dish, but not yet in actual __________ since we develop an immunity to the virus after ___________ For this technology to work, scientists will have to use a virus that the human body doesn’t _____________, yet doesn’t produce ___________ effects A virus called AAV, ___________ _________ virus, seems promising petri humans infection recognize harmful Adeno - associated
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Objective 1 Identify five complex patterns of heredity. polygenic
incomplete codominance Multiple alleles Sex-linked
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Objective 2 Describe how mutations can cause genetic disorders.
Mutations in your DNA produce faulty proteins that result in genetic disorders
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Objective 3 List several genetic disorders and describe their modes of inheritance Cystic fibrosis Simple recessive Tay-sachs Simple recessive Sickle cell codominant Hemophilia X-linked & recessive Huntington’s Disease Simple dominant
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Objective 4 Evaluate the benefits of genetic counseling.
Determine the chances of an offspring inheriting the disease Discuss treatment options
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