BIOL 3333 1st EditionExam # 3 Study Guide Lectures: 20-27Lecture 20 (March 9)Paracentric Inversion: Centromere not involvedPericentric Inversion: Centromere is involvedCrossovers in inversion heterozygotes: generate meiotic products w/ gene duplications and deficiencies Crossovers within a paracentric inversion: will produce a centric and dicentric products that contain duplications and deficiencies *since crossover gametes are likely to be inviable: inversions are used by geneticists to suppress recombination b/w chromosomes in genetic stocks -these are “balancer chromosomes” and usually have multiple inversions*Population polymorphisms that do not lead to clinical problems: are often associated w/ constitutive heterochromatin *Remember that “position effects” may influence expression- can occur when a gene in a euchromatic region of the chromosome is transferred into or near a heterochromatic block Fragile X Syndrome- approx. 8% of males w/ mental retardation - 1/1250 male births- large testes, prominent jaw and head, large ears- detectable as visible chromosomal abnormality on cell culture*when grown in special medium, individuals w/ fragile X chromosome will show narrowing orgap - fragile siteLecture 21 (March 11)Transmission pattern for fragile x: Pregnancies: - approx. 15% of all pregnancies result in sponantous abortions- 1/2 of these show chromosomal abnormalities- in approx. 1/200 live births, a chromosomal abnormality can be detected- majority of these is downs syndrome and balanced translocationsPrenatal Diagnosis: Amniocentesis- performed at about 16 weeks of pregnancy- this is when fibroblasts can be safely collected from amniotic fluid- requires mitogenic stimulation of cells prior to analysisChorionic Villus Sampling (CVS)- can be performed around the 9th week of pregnancy- from extra embryonic cells which are actively dividingDrosophilia Mitotic Chromosomes: - 4 pairs, 2n=8- 2 acrocentrics (XX)- two sets of metacentrics (2-3)` - one pair of dot chromosomes Polytene Chromosomes in Drosophila:- in salivary glands of larva, chromosomes undergo DNA replication without ensuring segregation- chromosomes will replicate approx. 10 times - giving rise to structures contains 1024X the amount of euchromatic DNA - DNA associated w/ the centromeric heterochromatin will be under replicated relative to DNA of the arms - will fuse to form a chromocenter*every chromosome arm has distinct binding pattern*changes in binding pattern could be correlated to changes in data generated from linkage analysisLecture 22 (March 13)Departures from Diploidy in Plants- tolerances for aneuploidy and polyploidy contribute to speciation- can propagate from somatic tissue- increases in ploidy may lead to increases in plant size- tolerances for anueploidy and polyploidy may facilitate genetic manipulation- monoploids can be generated fem gametes and used in selection experiments - chromosome number can be doubled (colchicine treatment) restoring ability to propagate sexually Polyploidy in plants-polyploid species - number of complete chromosome sets - autopolyploids: contain multiples of the same chromosome set (same species)- allopolyploids: contain multiples of different chromosome sets (different species) - hybridizations b/w related species may lead to pairing problems during meiosis*triploids are often sterile due to pairing problems during meiosis*even numbers of chromosomes in polyploids may lead to more normal segregation and partitioning of chromosome sets*If paring partners can be provided for homologs in allopolyploids: sterility can be relieved The study of Mutation and Bacterial Genetics - no genetics w/ out variation - most of the phenotypic alterations we have discussed thus far may be classified as “point” mutations: single base pair change or alteration in a small number of bases Classification of Point Mutations- DNA level- Transition: purine to purine; pyrimidine to pyrimidine - Transversion: purine to pyrimidine; vise versa Classification of Mutations- Protein level- silent mutation: GGG GGC both glycine- synonymous mutation: AAA AGA both positively charged (basic)- missense mutation: CGC CCC (arg to pro - charged to neutral)- nonsense mutation: CAG UAG (amino acid signal to stop signal in protein synthesis)Mutant Types- Morphological mutations: affect outwardly visible properties- lethal mutations: loss of viability; change in characteristics ratio or number of recovered progeny- biochemical mutations: can lead to changes in the growth requirements ofan organism- conditional mutations: - Particular environmental conditions may affect whether an allele exhibits a particular phenotype- Permissive conditions: the allele produces a functional gene product- Restrictive conditions: the allele produces a non-functional or sub-functional gene product*coat color in siamese cats - temperature sensitive mutation in melanin productionLoss of Function Alleles- loss of function; generally recessive, lead to decrease in amount of gene product- null alleles: no gene product produced- weak or “leaky” alleles: some gene product still being produced- haplosufficient vs haploinsufficient: - is one copy of a wild type allele capable of a wild type phenotype?Gain of Function Alleles- gain of function: can be dominant - a mutant phenotype can arise even in the presenceof a wild type allele- mutation may produce a new function or altered function- eg. receptor now capable of responding to extracellular signal without binding that signal Lecture 23 (March 23) Bacterial Growth Characteristics- Prototroph: an organism with wild type growth requirements; will be able to grow on minimal medium- Auxotroph: an organism that will proliferate only when the media is supplemented with some specific substance not required by wild type organismsStudies on Bacteria: - 1943: The Delbruck Luria Fluctuation test- designed to determine if variant phenotypes were due to physiological adaption of the bacterial cells or to random mutation- test based on a statistical argument Lecture 24 (March 25)The F Factor: - F + cells = donor strain- F- cells = recipient strainDonor cells contain a genetic entity ( F factor) that determines donor status- F factor must be replicated and transferred to recipient; F- cells in culture become F+- F factor mediates directed transfer (eg genes for pili formation)- F factor exists as independently replicating factor (distinct from bacterial chromosome)- During