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Name: _______________ Date: __________ Period: ___ Dragonfly Chapter 14The Human Genome Section 14-1: Human Heredity Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders? I. Human Chromosomes A. Karyotype: A picture of chromosomes taken during mitosis, cut out and _______________ ________________________. B. Diploid cell: _____________ of homologous chromosomes Human diploid cell has _____chromosomes arranged in _____ pairs The 46 chromosomes contain __________________________________ of DNA Mendelian genetics requires that organisms ____________________________ of a gene from each parent. In humans, __________________ (reproductive cells of egg and sperm) contain a single copy of each gene (one set of genetic information). Gametes are formed in the __________ (sperm) and ___________ (egg) by meiosis. Each gamete contains 23 chromosomes (one set) or __________________ (N) of chromosomes. __________________ requires the egg and the sperm to join and produce a __________ (fertilized egg) that contains 46 chromosomes (two sets) or _________________ (2N). Humans have 46 total chromosomes 44 _________________ 2 ____________________ (X and Y) II. Human Traits A. Pedigree Chart: A pedigree chart shows the _________________ within a family and can be useful to help with ________________________ within families. It is another ____________________________ of a particular cross and the genotype of the family members. B. Genes and the Environment Phenotypes are determined by _______________ as well as _________________ influenced. Environmental influences on gene expression are ______________________ but genes are. III. Human Genes The __________________: Complete set of genetic information Composed of about 30,000 genes A. Blood Group Genes: Human Blood comes in a variety of genetically determined blood groups There are many different types of blood groups but the ones associated with the ABO blood group and the Rh blood groups are best known. Rh blood groups is controlled by single gene with ________________. It is another antigen in blood, first discovered in Rhesus monkeys. The arrangement of the alleles determines only _______ possible types _____________ (+) contains the antigen, or ___________ (-) doesn’t contain the antigen. Positive is ______________ over negative. Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/RhRh-negative is identified with one genotype: Rh-/RhABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is classified into four types: _____________ due to the presence or absence of specific _______________ in the blood. Alleles IA and IB are codominant and io is recessive to both IA and IB Antigens are ________________ used by the immune system. When an unrecognized antigen is present an immune response takes place and the cells ____________________________. Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions To From B. Recessive Alleles: Trait controlled by a recessive allele. This results in the disorder being present ___________________________. Examples include: PKU (Phenylketonuria), Tay Sachs disease and Cystic Fibrosis, Albinism, and Galactosemia (See chart on page 345) C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder being present when __________________________. Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s Disease Huntington Disease: It is controlled by a _______________________. The gene is located on Chromosome #4 Genetic degenerative disease that shows no symptoms until a person is in their _________ __________. It progresses with gradual degeneration of their nervous system leading to loss of muscle control and mental function until death occurs. Question? Would you want to know now if you could potentially get Huntington’s disease when you are older? Would you want to know if you could pass the gene on to your offspring before you have children? D. Codominant Alleles: controlled by _______________________________________. Sickle Cell Anemia is such a disorder. IV. From Gene to Molecule The link between _____________________________ is not easily determined but for several diseases we have been able to make the connection. For both _____________________ and ______________________ a small change in the DNA of a _____________ affects the ____________________________, causing a serious genetic disorder. A. Cystic Fibrosis: (See figure 14-8 p. 347) Cystic Fibrosis a.k.a. “CF” is a common genetic disease. It is most common in people of Northern European decent. It is a _______________________ of a gene found on the # 7 chromosome and affects the ____________________________ ____________________. It is caused by the _______________________ in the middle of a sequence for a protein and causes the protein to be ______________ and doesn’t allow Chloride ions to transport across the membrane, as they should. This causes the cells in a person’s airways to be unable to transport chloride ions and become ______________________________. B. Sickle Cell Anemia The patient’s blood cells are irregularly shaped, _________________, and this is how the disease got its name. In normal red blood cells the _________________________ carries ___________ and distributes it around the body. In sickle cell disease, the red blood cells are sickle– shaped, causing the blood hemoglobin to no longer carry oxygen as well and _____________________ ___________________________. This person is deprived of oxygen and the result is physical weakness, and damage to the brain, heart, spleen. It may be fatal. The cause: A _________________ in the DNA that codes for Hemoglobin polypeptides is changed. This substitutes Valine for glutamic acid. This change makes the hemoglobin less soluble in blood. This will cause the hemoglobin to come out of the blood and _______________. This crystallization causes the ________________ of the blood cells and the medical consequences. The genetics: The allele for sickle cell (HS) is codominant with the allele for normal hemoglobin (HA). Heterozygotes (HS HA) are said to be ________________________ and have some effects of the disorder because they have both normal and sickle cell blood hemoglobin. The distribution: Sickle Cell anemia is most prevalent in people of __________descent. 10% of African Americans and 40% of populations in Africa and Asia carry the gene for Sickle cell anemia. Why? The carriers for the disease have a ___________________________, a dangerous disease caused by a blood parasite found in tropical areas of the world. (See figure 14-10 p. 348) Sickle Cell Anemia is a ______________ that has provided an ___________ in Malaria prone areas and in these areas it is ________________________________ and therefore Sickle Cell Anemia persists. Section 14-2: Human Chromosomes Key concepts: Why are sex-linked disorders more common in males than in females? What is nondisjunction, and what problems does it cause? I. Human Genes and Chromosomes Human diploid cell contains ______________________ of DNA. All neatly packed into the 46 chromosomes. __________________ of the DNA actually functions as genes. Genes are located on the chromosomes and each gene occupies a ______________________ on a chromosome. Genes may exist in ____________________ (alleles) Each chromosome contains ______ of the alleles for each of its genes Chromosome #21 and 22 are the ____________ of the human autosomes. These were the first two chromosomes whose sequences had been determined. Both also contain genes for some genetic disorders like ________________________ ___________________________ We also discovered that there are many _________________________ segments of DNA Human chromosomes also have _______________________ that can cross over just as we saw in the fruit fly. II. Sex-linked Genes 1. _______________________ are the ones that __________ in males and females 2. chromosomes that are the ________ in male and females = _______________ 3. In humans: females = ____ and Males = ______ 4. The Y chromosome is smaller than the X A. Sex Determination 1. female _______________ carry an X chromosome 2. _________ gametes can carry either an X or Y (meiosis segregates the chromosomes; _______ of the sperm carry X and ______ of the sperm carry Y) 3. In humans, ____________________________________ of an offspring Female: XX male: XY 4. In some animals such as birds, butterflies, and some fish, the female determines the sex because she has the ______________ chromosomes. B. Sex-linked Genes 1. In addition to determining the sex of an individual, the sex chromosomes carry genes that __________________________. May be on the X or Y chromosome, ________________________________________ _____________________________________________________ Most often seen in _____________ because they only have one X chromosome and thus all alleles are expressed even if they are recessive. Colorblindness is a recessive disorder in which people can’t distinguish between certain colors. _________________ colorblindness is most common. XC and Xc are ________________ for normal and colorblind vision. XC XC and XC Xc are ________________________________. XC Xc is a _______________________ and can pass the gene on to her sons. Xc Xc is a _____________________. XC Y is a __________________ and Xc Y is a _________________. Hemophilia is a _________________________ in which one is unable to clot their blood. Also known as ____________________. Individuals with hemophilia can bleed to death from minor cuts and may suffer internal bleeding from a bruise. Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is missing. Muscular Dystrophy is another ____________________________. Here the affected individual inherits a degenerative _________________disorder. In which there is a progressive weakening and loss of skeletal muscle. The gene that codes for a _________________ is defective. They rarely live past early adulthood. Treatments are being explored that _________the defective gene. III. X-Chromosomes Inactivation Males survive with only one X chromosome so, what do females do with 2? They _________; it becomes inactive. This creates a dense region in the nucleus known as a ______________. This is seen in coat color in cats. The cells will randomly shut off the coat color allele in one X chromosome and turn them off in the other X chromosome in other cells and this leads to some areas that are spotted orange and some spotted black, creating a tricolor cat, ________. This only happens in __________ because males only have one X chromosome. IV. Chromosomal Disorders Whole/sets of chromosomes mutations 1. _________________ = failure of homologous chromosomes to separate normally during meiosis. This results in a disorder of chromosome numbers. Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II 2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome Nondisjunction disorders: Disorders in which the failure of _____________________ during one of the stages of meiosis causes a gamete to have _______________________________. Nondisjunction can occur in _________________________________. Down’s Syndrome: Down’s syndrome is an example of _____________________________, specifically chromosome 21. In Down’s syndrome there is an _________________ of chromosome 21 (trisomy 21). Doing a _________________ (display of all the chromosomes in a cell nucleus) and looking at the chromosomes under a microscope detect the extra chromosome. Characteristics of Down’s syndrome include _________________, physically challenged, facial irregularities, and often heart defects. Turners Syndrome: Nondisjunction of the sex chromosomes in which __________________ ______________. They have the chromosome makeup of ________ where O represents the missing chromosome. This individual is female in appearance but does not develop the female sex organs during puberty and is ____________. Klinefelter’s Syndrome: Nondisjunction of the sex chromosomes in which an extra ____ ____________________ is present. They have the chromosome makeup of ___________. They are _________ in appearance and are also sterile. May also be 48 XXXY or 49 XXXXY No nondisjunctions of the sex chromosomes have ever produced and survived without an ___ ________________. This is because the X chromosome carries many genes _____________ ____________ The impact of the sex chromosome nondisjunction has led us to understand the importance of the ________________________ in determination of sex of an individual. This has recently been determined to be true because the Y chromosome has been found to have a gene that turns on ________________________________ in the embryo even if many X chromosomes are present.