Genetics Exam 3 ReviewCh. 8Centromeric locations on chromosomes (P=Short arm, Q=Long arm):Metacentric: Perfectly centeredSubmetacentric: Slightly off centerAcrocentric: Q 2x longer than PTelocentric: Centromere on top, only see Q armAlterations of chromosome structure:1. The total amount of genetic infor in the chromosome can changea. Deficiencies/Selections b. Duplications 2. The genetic material remains the same but is rearrangeda. Inversionsb. Translocations Deficiencies: When they have a phenotypic effect, usually detrimentalTerminal deletion: Edge of chromosome is lost, single breakInterstitial deletion: two breaks and reattachment of outer piecesEx. Cri-du-chat: 46, 5p-Duplications: Repetitive sequences can cause misalignment between homologous chromosomes, if crossing over occurs, nonallelic homologous recombination resultsUsually don’t cause harmful syndromesDuplicated genes can be passed on through families and evolve to have similar but distinct functions: Gene familyOrthologs: Same gene in different speciesParalogs: Different versions of same gene in same species (caused by duplications)(Both of homologs)Copy Number variation: Small but significant DNA varies in copy number among members of same species. Common, 1-10% of genome1. Schizophrenia2. Autism3. Susceptibility to infectious disease4. CancerRed- Green color Vision: May have multiple copies due to mispairing and unequal crossing over, makes color-blindness more likely.Inversions: Segment that has been flipped into the opposite orientation1. Pericentric inversion: Centromere lies within inverted region2. Paracentric inversion: Centromere lies outsides inverted regionUsually has no effect because all the genes are still thereTranslocation: One segment of one chromosome becomes attached to another● Caused by chromosomal breakage and DNA repair or Abnormal Crossovers.1. Reciprocal translocations: Two nonhomologous chromosomes exchange genetic material2. Unbalanced translocations (Simple): Exchange only occurs in one direction, cause phenotypic abnormalities like familial Down Syndromea. Majority of chromosome 21 is attached to chromosome 14Robertsonian Translocation: Ex. Familial Down Syndrome● Breaks occur at the extreme ends of the short arms of two nonhomologous acrocentric chromosomes● Small acentric chromosomes are lost● Larger fragments fused to their centromeric regions to form a single chromosomes whichis metacentric or submetacentricMeiotic segregation can occur in one of 3 ways:1. Alternate segregationa. Chromosomes on opposite sides of the translocation cross segregate into the same cell, leads to balanced gametes2. Adjacent-1 Segregationa. Adjacent non homologous chromosomes segregate into the same cell, leads to unbalanced gametes3. Adjacent-2 segregation (RARE)a. Adjacent homologous chromosomes segregate into the same cell, leads to unbalanced gametes.Chromosome numbers can vary in two main ways● Aneuploid: Variation in the number of complete sets of chromosome ○ Occurs occasionally in animals, frequently in plants● Aneuploidy: Variation in the number of particular chromosomes within a set○ Regarded as abnormal conditionsTrisomy 13: Patau-Mental and physical deficiencies wide variety of defects in organs, large triangular nose, and early deathTrisomy 18: Edward- Mental and physical deficiencies, facial abnormalities, extreme muscle tone, early deathTrisomy 21: Down- Mental deficiencies, abnormal pattern of palm creases, slanted eyes, flattened face, short staturePolyploids having an odd number of chromosome sets are usually sterile1. Seedless fruit2. Seedless flowersNatural Ways that vary chromosome number1. Meiotic nondisjunction: Produce haploid cells that have too many or too little chromosomes, offspring would have abnormal chromosomal composition2. Mitotic abnormalities: One chromosome less cell is nonviable, other is already a diploid cell and can participate in fertilization but will yield a triploid offspring3. Interspecies crosses: A much more common mechanism for changes in the number of sets of chromosomes is alloploidyAllotetraploid: Contains two complete sets of chromosomes from two different speciesSpecies A has 2n = 16 chromosomes and species B has 2n = 14. How many chromosomes would be found in an allotriploid of these two species?22 or 23. 16+7=23 14+8=22Mitotic Abnormalities1. Mitotic disjunctiona. Sister chromatids separate improperly, causes trisomic and monosomic daughtercells2. Chromosome lossa. One of the sister chromatids does not migrate to a pole, causes normal and monosomic daughter cellsGenetics abnormalities that occur after fertilization lead to mosaicism Part of the organism contains cells that are genetically different from other partsPolyploid and allopolyploid plants often exhibit desirable traits for breeders try to make these mutations happen. The drug colchicine binds to tubulin and promotes nondisjunction.Fragile Sites: More susceptible to chromosomal breakage, indicates regions of non-tightly coiledchromatin. Can be linked w lung cancer, associated with regions of short tandem DNA sequence repeats.Fragile X syndrome: Folate-sensitive site on X chromosome exhibit FXS, more common form of inherited mental retardation;Dominant trait.Ch. 10Hershey and Chase: Study bacteriophage (Made up of only DNA and protein) They marked DNA (phosphorus) and Protein (sulfur) with markers and allowed the virus to infect E. Coli, the infected cells contained the marked DNA but no marked proteinRetroviruses● Replicate unusually● RNA serves as template for DNA synthesis● Complementary synthesis of DNA by RNA-dependent DNA polymerase reverse transcriptaseNucleic Acid Structure1. Nucleotides form the repeating units2. Nucleotides are linked to form a strand3. Two strands can interact to form a double helix4. The double helix folds, bends and interacts w proteins resulting in 3-D structures in the form of chromosomesNucleotides: A phosphate group, a pentose sugar, a nitrogenous baseNucleoside: A base and sugarPurines: Doubles ring: Adenine and GuaninePyrimidines: Single ring: Thymine, Cytosine, and Uracil (RNA)Bases are always attached to the 1’ Carbon on the sugarPhosphate group is always attached to the 5’ carbon on the sugarRNA or DNA is determined by if there is an O on the 2’ Carbon on the sugarNucleotides are covalently linked together by phosphodiester bonds, connects 5’ carbon of one nucleotide of the 3’ of another. Bonded between sugar and