GeneticsF07[1] - Single Gene Traits: Earlobes Single...

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Unformatted text preview: Single Gene Traits: Earlobes Single phenotype: a product/trait resulting from a gene Alleles Alleles alternative forms of a gene we inherit 2 alleles of every gene (1 from we mom, 1 from dad) mom, Alleles for Earlobe Shape: Alleles Attached: recessive, f Free: dominant, F gene: section of DNA that codes for earlobe shape 2 possible alleles: attached (f), free (F) OR f F But! You have 2 parents – each donated a chromosome Dad Mom OR f OR AND F f F Genotype genotype: the specific set of alleles contained in you Mom Dad ff OR OR Ff Ff f F FF f F Describing the allele Describing combination: combination: homozygous: alleles are the same on alleles homologous chromosomes (FF or ff) homologous heterozygous: alleles are different (Ff) Homologous chromosomes: - code for same set of genes - occur in pairs, 1 from each parent Dad Mom How many homologs of a How given chromosome? given 2 Diploid (2n) 1 Haploid (1n) 3 Triploid (3n), etc. . . where n = number of different kinds of where chromosomes chromosomes Attached Attached Free Attached Attached recessive, f Free dominant, F Individually, build a set of chromosomes to reflect your genotype – draw them. Mom Mom f F Dad Clicker: What is the correct representation for a free-lobed heterozygote who’s mother has attached lobes? B A f F D C f f F E f F F f F sister chromatids sister chromatids centromere Clicker: What is the correct representation for the duplicated state of: f B A D F C E Cells Must Divide For: Cells Growth (Mitosis) Sex (Meiosis) Copy DNA to ensure that each new cell Copy gets the complete set gets Pair of unduplicated homologous chromosomes Gene of interest: hitchhiker’s thumb T = straight t = hitchhiker Hitchhiker Hitchhiker t t Non­hitcher? Non­hitcher T T T OR t Pair of unduplicated homologous chromosomes T t 1. Build these chromosomes in the duplicated state. Cell Division by Mitosis: Cell Produces identical “sister cells” 1 diploid cell 2 diploid cells diploid T T Pair of unduplicated homologous chromosomes t T t t Pair of duplicated homologous chromosomes Nucleus T Mitosis T t t Cell T T t t T T Mitosis t t Mitosis T T T t T t t t Cell Division by Meiosis: Cell Produces Gametes (sex cells) 1 diploid cell 4 haploid cells diploid Two Divisions: Meiosis I: Homologs Separate Meiosis II: Sister Chromatids Separate Pair of unduplicated homologous chromosomes T t Build these chromosomes in the duplicated state ­ T Meiosis I T t t T Meiosis I T t t T t t Homologs separate Meiosis I T T T t t T Meiosis II T t t T T Meiosis II T t t Sister Chromatids separate T t t T T t t From a heterozygote parent, (genotype = Tt) 2 types of gametes formed: “T” or “t” Problem 1: Draw Meiosis for Pair 22 22 Use your model to show exactly when and Use where the mistake occurred that resulted in the genotype for Trisomy. the Draw individually - consult with your group. Problem 2: Draw the Punnett Square and calculate the ratios of both phenotypes and genotypes for the offspring of: offspring Cross 1: heterozygous female with an Cross attached-lobed male. attached-lobed Making things a bit more complex: Making Meiosis with two genes found on two Meiosis different chromosomes: keeping track of both the hitchhiker and the earlobes! both Follow along in Mirkov: 2 chromosomes, 2 genes, each with 2 alleles T t F f Step 1: Chromosomes duplicate T t T t F Ff f Step 2: Meiosis I: Homologs Separate T T F F t t f f Step 3: Meiosis I: Homologs Separate T T F F t t f f Step 4: Meiosis I: Homologs Separate 2 cells T F T F t t f f Step 5: Meiosis II: Sister Chromatids Separate T F T F t t f f Step 6: Meiosis II: Sister Chromatids Separate 4 cells T F T F t f t f What if homologs lined up differently at Meiosis 1? (Independent Assortment) T T t t How many different kinds of gametes could be formed? F F f f How many different kinds of gametes could be formed? T T TF t t Tf tF tf F F f f How many different kinds of gametes could be formed? T T t t TF Tf tF tf = 2n F F f (for diploid organisms, where n is the # of f homologous pairs; in this case n = 2) Humans, n=23 so, 223 = 8,388,608 is the number of different kinds of gametes 1 person can make. How many different kinds of zygotes could 2 people form?? How many different kinds of zygotes could 2 people form?? 8,388,608 x 8,388,608 (or, 8,388,6082) = 70,368,744,177,664 !!!! potential chromosome combinations Does meiosis/mitosis make “mistakes”? “mistakes”? Trisomy 21 (Down’s Syndrome) Syndrome) 1 in 800 live births Trisomy 18 (Edward’s) Trisomy 1 in 8,000 pregnancies < 30% survive 1 month 30% pregnancy pregnancy Klinefelter’s Syndrome Klinefelter’s XXY (male) tall (6’ – 7’ +) hypogonadism infertile female 2ndry sex characteristics iinfertile (non-motile sperm, if nfertile produced) produced) sometimes: osteoporosis delayed motor/social/learning delayed skilss skilss Turner Syndrome Turner X (female) underdeveloped female underdeveloped 2ndry sex characteristics 2ndry short (avg. 4’8”) amenorrhea iinfertility (non-functional nfertility ovaries) ovaries) spatial/temporal relations Cancer Cells from Female Colon Colon Predict the outcome of the following crosses. Draw the Punnett Squares and calculate pheno/geno ratios. calculate 1. 2 free-lobed heterozygotes? 1. 2. a male heterozygote with an attached2. lobed female? 3. an attached-lobed female with a freelobed homozygous male? ...
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