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Lecture 13

LECTURE 13.docx

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Steve Joordens

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LECTURE 13 DNA: Quiz- WE ARE ALL MADE UP OF DNA • How many nucleotides are in Deoxyribonucleic acid (DNA)? 4 NUCLEOTIDES (A,G=PURINE ; C,T=PYRAMIDINE) • Where is DNA found? NUCLEUS • How does DNA methylation change the way exons are transcribed in the lipophorin receptor gene of Camponotus ants? Rhino DNA • How could researchers distinguish the DNA of African rhinoceros (Diceros bicornis) from Indian Rhinoceros (Rhinoceros unicornis?) Probe to catch rhino poacher Rhinoceros horn—the natural, but politically incorrect version of viagra—can now be protected from poachers using DNA technology. Scientists at the National Institute of Immunology in India (NII; New Delhi) have just completed six months of tests on a DNA detection device that has not only been shown to detect rhino horn but also to tell whether the specimen comes from India or elsewhere. "It will be a valuable weapon in the hands of conservationists wanting to track down the source of rhino horn in the illegal market," says Sher Ali, head of NII's molecular genetics laboratory. Ali and his colleagues have discovered a repetitive 906 base pair DNA sequence that is unique to India's one-horned rhinoceros (Rhinoceros unicornis). The sequence is not present in the closely related African double-horned black rhinoceros (Diceros bicornis) or any other species of rhino. "This distinguishing feature will help identify if a particular horn came from India or Africa," says Ali. The great Indian one-horned rhino is an endangered species— currently numbering about 2000—and is confined to three or four protected forests in Assam and West Bengal in eastern India. • DNA from poached rhinoceros horn compared to reference samples Lecture 14: Chromosomes: Quick Quiz • How many chromosomes do humans have? 46 diploid, 23 haploid • What is the composition of chromosomes in a skin cell and a sperm cell? Skin cell- 46 chromosomes, diploid Sperm cell- 23 chromosomes, haploid • How does mitosis change the number of chromosomes? In interphase, the DNA is replicated not in mitosis. Mitosis separate the duplicated chromosmes and put them in each cell. Thus each daughter cells have the same chromosome number with the original cell. Polytene chromosomes from salivary gland= 4 chromosomes Aneuploidy- diploid number is not multiple of haploid number -chromosome abnormality: missing or extra chromosome Haplodiploidy- sex determination system -males are haploid; females are diploid -eg. Ants and bees Heterogametic-WZ (female birds) Homogametic- ZZ (male birds) **Grasshopper- XX(even chromosome #) X(odd chromosome number) **Zebra fish- region in chromosome 4?-still in research CELL CYCLE G1/S phase transition is important because one of the hallmarks of cancer is the loss of normal control of the transition. Cytokinesis usually begins while mitosis is still in progress. In animals: FURROW-contractile ring is made of microfilaments, motor proteins move like draw strings In plants: CELL PLATE- vesicles in the midpoint plane, extend across, eventually become cell plate THE F FACTOR AND CONJUGATION The transfer of genetic material during conjugation: A. Transfer of the F factor - NO CHROMOSOMAL DNA IS TRANSFERRED. JUST THE fertility plasmid of (F factor) B. Transfer of bacterial genes - F factor integrates with the chromosomal DNA becomes (HfR CELL) - Recombination during the cross over during the transfer of F+ to F-, conjugating pair breaks apart. - The recipient remains F- since not all the F factor is transferred. **The inverted repeat sequence is an IS element on both the F factor and the Bacterial chromosome that provides the homology needed for the creation of the Hfr strains. **In a number of bacterial transposons, the inverted repeat sequences are insertion sequences, which provide the transposase (this is the central region which contains antibiotic resistance) for movement of the element. These non-IS genes included in transposons are carried along as the TEs move from place to place.  conjugation LECTURE 15 Meiosis and Heredity: Quick Quiz • How many chromosomes do humans have from their mother? 23 CHROMOSOMES, HAPLOID • How many sets of chromosomes are in: A cell during anaphase I? diploid A cell during anaphase II? haploid How does meiosis change the number of chromosomes? * What strain of E. coli caused illness? ………………………………………………………………………………………………………………………………………………………………… Trisomy x female xx+x Turner’s syndrome x+ 0 Male klinefelter’s xx+y GENETIC VARIABILITY DURING MEIOSIS; 1. GENETIC RECOMBINATION 2. RANDOM SEGREGATION IN PROMETAPHASE I  ANAPHASE I 3. ALTERNATIVE COMBINATION AT MEIOSIS II- RANDOM ASSORTMENT IN METAPHASE II  ANAPHASE II 4. RANDOM FERTILIZATION TRANSPOSABLE ELEMENTS IN EUKARYOTES Mapping the alleles by linkage studies produced a surprising result: the map positions changed frequently, indicating that the alleles could move from place to place in the corn chromosomes. Calico cats • Genetic mosaic: Inactivated X-chromosome is cell independent: some cells have inactivated maternal chromosomes others have inactivated paternal chromosomes EPISTASIS -gene for the orange fur is on the X chromosome LECTURE 16 Peas: Quick Quiz • How many phenotypes would you expect among the progeny of the following genetic cross: • RRYYTT x rryytt ? • What is the genotype of a pure-breeding purple-flower pea plant? PP • How does independent assortment explain Mendel’s experimental data with dihybrid crosses in pea plants? THE COMBINATION OF DIFFERENT ALLELES PAIR INDEPENDENTLY • Product rule: The probability of two independent events occurring simultaneously is the product of each of their respective probabilities • Sum rule: The probability of either of two mutually exclusive events occurring is the sum of their individual probabilities. LECTURE 17 Pedigrees: Quick Quiz • How many phenotypes would you expect among the progeny of the follow
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