Week two genetics
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This 3 page Class Notes was uploaded by Katlyn Burkitt on Friday September 16, 2016. The Class Notes belongs to BIOL 309 at Towson University taught by Dr. Bulmer in Fall 2016. Since its upload, it has received 8 views. For similar materials see Genetics Lecture in Biology at Towson University.
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Date Created: 09/16/16
Sep 12 A female who is a carrier for colorblindness and hemophilia mates with a male who is colorblind what children could they have? o c c h X Y x X X o X X , X X ,X y, X y h c h c o Or she could have both X X x X Y SRY gene o The hormone found on the y determines whether an offspring is male or female o It can cause males with two X chromosomes or vice versa Gender testing in sports o Not done at the elite level o Smenya 800-meter runner who was recently required to do a drug and gender test In reptiles the gender is determined by temperature In some species the heterogametic sex is female and the homogametic sex if male Haplodiploidy o Males are derived from unfertilized eggs Sep 14 Haplodiploidy o In the hymenopter (ants, bees, and wasps and other insects) males come fom unfertilized eggs o No meiosis in males only mitosis o Males do not have a father or sons but can have grandsons Evolution of Eusociality Haplodiploidy and eusocial hymenoptera Relatedness o Sister relatedness in the hymenoptera Daughters receive all of their father’s genes and half of their mother’s genes Problems with the haplodiploid explanation for eusociality o Assumes all workers have the same father (Problematic because honeybee queens typically mate with 17+ males) o In a lot of species more than one female founds a nest o There are many eusocial species that are not haplodiploid What percentage of female’s X linked genes are shared on average with her sister? Her brother? o X X x X Y 1 or 2 1 or 3 1 or 2 X X or X X then for sons X Y For sisters o 75% of DNA shared 50% for maternal X and 100% for paternal Average together 100% + 50% = 150%/2 = 75% For brothers and sisters 25% of DNA shared o 50% for maternal X chromosomes o 0% for Y chromosome o Average together 50%+0%= 50%/2= 25% Aneuploidy in sex chromosomes o XXY Trisomy (1/500 – 1/1000 boys) Klinefelters syndrome: Sexually underdeveloped (Low testosterone) long limbs and large hands and feet, may develop breast tissue, usually infertile, no mental retardation X-inactivation excluding a few genes in the pseudoautosomal region o Triple X syndrome (1/1000 girls) tallness, menstrual irregularities, slightly reduced intelligence when compared to XX siblings, fertile No unusual physical features or medical problems Only one X is active at a time o XYY Jacobs Syndrome (1/1000 boys) tallness, acne, and speech and reading problems in some cases Used to be associated (1960’s) with criminal behavior Usually occurs due to nondisjunction during meiosis II Not affected by advanced paternal or maternal age Monosomy o XO Turners Syndrome (1/2500 girls) Sexually undeveloped, short, skin flaps on the back of neck, sterile, normal intelligence, 99% die before birth Deletions – Hypoploidy for region deleted, typically lethal if the deletions occur on both chromosomes o Cri-du-chat syndrome, 5p minus syndrome (1/20,000-50,000) Deletion of short arm of chromosome 5 Mental and physical impairment, cat like crying noises, <5year lifespan Duplications of chromosome segments o Hyperploidy partial trisomy for duplicated region Rearrangements- no variation in chromosome number o Inversions- Piece of a Chromosome detaches and rotates 180 degrees and reattaches to the same chromosome Translocations o Piece re-attaches to a non-homologous chromosome Mosaicism o Autosomal and sex chromosome aneuploidy only occurs during mitosis o One daughter cell receives both chromosome duplicates or none Sep 16 Sep 16 Linkage: Close to each other on the same sister chromatid, therefore they are typically inherited together (They are so close together they are affectively the same genes Recombination frequency: A testcross used to determine the frequency of crossing over o Recombination refers to “crossing over” or the pairing of gens from different chromosomes Total number of recombinants/ total number of offspring = frequency of recombination If linked the 0%-50% is the frequency if sorting independently then its 50+ Genetic distance and physical distance o Crossing over is less likely to occur near telomeres or centromeres (heterochromatin) : Short genetic distance compared to physical distance Looking at 3 genes o To determine the distance between two traits Step one determine if there has been any recombination Add up all recombinants and divide by total number of individuals = the distance between them Beware of double recombinants
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