Biology 101 Chapter 8 Notes
Biology 101 Chapter 8 Notes BY 101
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This 5 page Class Notes was uploaded by Alexandria Thomas on Tuesday October 18, 2016. The Class Notes belongs to BY 101 at University of Alabama at Birmingham taught by Mickie L Powell in Fall 2016. Since its upload, it has received 4 views.
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Date Created: 10/18/16
Biology Notes Chapter 8 DNA Detective: Complex Patterns of Inheritance and DNA Profiling Introduction July 16, 1918, the Romanov family was killed Nicholas II, the tsar of Russia Alexandra, the tsarina Their five children Four family servants Could a mass grave in Ekaterinburg hold their remains? Bones Sex Age Blood Types Y Chromosomes genes Genes Sequences of DNA that code for RNA and /or proteins. The expression of genes determines the physical Many organisms have at least 2 copies of each gene (one from each parent) What if they are for different versions of the same trait? _________________ genes mask the phenotype of ____________________ genes. 8.1 Extensions of Mendelian Genetics Incomplete dominance: a heterozygote expresses an intermediate, “blended” phenotype RR= red flower rr= white flower Rr= pink flower Codominance: the heterozygote’s phenotype is a combination of two fully expressed traits R R = red coat color in cattle 2 2 R R = white coat color in cattle R R = roan coat color (red and white) ABO blood group has three alleles of one gene: A f is dominant to f is dominant to A B f and f are Individual genotypes will show two of these alleles. Multiple alleles: more than two alleles of a gene are possible ABO blood system Type A has sugar A on the surface of blood cells Type B has sugar B on the surface of blood cells Type O has no suagrs on the suface of blood cells Type AB has suagr A and suagr B on the surface of blood cells Rh factor: presence or absence of Rh surface protein Rh = presence of the Rh protein (dominant) Rh Rh or Rh Rh+ Rh = absence of the Rh protein (recessive) RhRh Blood type analysis: can be used to exclude potential parents AB parent can never have an O child Two Rh parents can never have a Rh child. Polygenic Traits: Bone size and structure Genetic traits of Romanov skeletons could not be determined by simple phenotype comparison. Pleiotropy: the ability of a single gene to cause multiple effects on an individual’s phenotype. Hemophilia: blood clotting disorder Protein (clotting factor VIII) is not produced. Prince Alexis inherited the hemophilia allele from his mother. Gene for this clotting factor is on the X chromosome. 8.2 Sex Determination and Sex Linkage Chromosomal sex determination Humans have 22 pairs of autosomes and one pair of sex chromosomes. Women: two X chromosomes Men: one X and one Y chromosome Sexlinked genes: Any of the genes found on the X or Y sex chromosome Xlinked: located on the X chromosome Males inherit the X from their mother. Males are more likely to express Xlinkage Carry only one X chromosome Females are less likely to express Xlinkage. Must carry two defective X chromosomes Ylinked: located on the Y chromosome Passes from father to sons SRY gene, which leads to the development of the testes Romanov bones were tested for DNA sequences found only in Y chromosomes. All bones belonged to girls. Carriers: heterozygotes without the condition Only females can be carriers of Xlinked recessive traits. Hemophilia Redgreen color blindness Duchenne Muscular dystrophy 8.3 Pedigrees Pedigree: a family tree; shows trait inheritance through several generations Circles and squares are commonly used symbols in pedigrees. Modes of Inheritance Pedigrees reveal modes of inheritance Autosomal dominant trait Pedigree for an autosomal recessive trait Pedigree for an Xlinked trait 8.4 DNA Profiling Romanov mystery Limited blood typing and karyotyping information required more sophisticated techniques to answer these questions: 1. Which of the bones from the pile are actually different bones from the same individuals? 2. Which of the adult bones could have been from the Romanovs, and which bones could have belonged to the servants? 3. Are these bones actually from the Romanovs, not some other related set of individuals? DNA profiling: technique to identify individuals based on DNA sequences Genome: Entire suite of genes present in an organism Only 13 different sequences of DNA found in all humans are used. Show variations in length between different individuals. Can be separated by size into banding pattern Relatives have more common bands Short tandem repeats (STRs): the 13 genome regions used for DNA profiling Adjacent repeats of short DNA sequences Individuals have different numbers of the repeating sequence. GATC One person has two repeats (GATCGATC) One person has three repeats (GATCGATCGATC) Polymerase chain reaction: process that amplifies (creates many copies of) the DNA sequence DNA is mixed with nucleotides, specific primers and Taq polymerase, and then is heated and cooled. Repeated heating and cooling unwind and separate the DNA helix. Taq polymerase (a heatresistant enzyme) builds new DNA using separated strands as templates. Continued heating and cooling produce more DNA copies Each cycle of PCR, the amount of DNA doubles Gel electrophoresis: process that uses electric current to separate DNA fragments by size Copies STRs are added to agarose gel. Electric current is applied. Smaller fragments move more quickly through the gel. DNA profile comparisons Each of a child’s bands must be present in one or both of the parents Childsized skeletons from the Ekateringburg grave are related to Adult 1 and Adult 3. Two questions answered by scientific analyses Nine different individuals were buried in the mass grave. Two of the adult skeletons were the parents of the three children. Romanov mystery: Did the bones belong to the Romanovs? DNA from living and exhumed relatives was tested and compared to the DNA profiles of the bones. Adult male skeleton (related to the children) was related to Prince Philip, the tsarina’s grandnephew. Conclusion: the bones in the graved belonged to the tsar, the tsarina, and three of their children, as well as four servants.
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