1. Miss Sofa Paz

2. Each chromosome has a twin that resembles it in size and shape.One comes from your mother and the other one from your father. 3. Is a set of one maternal chromosome and onepaternal chromosome that pair up with eachother inside a cell during meiosis. Carries the same sequence ofgenes in the same locations,or llooccii.. Controls the same inheritedcharacteristic. The genes may be slightlydifferent versions. 4. A pair of chromosomes havingthe same gene sequences, eachderived from one parent. Two identical halves of a singlereplicated eukaryoticchromosome.Sister chromatids are identical unlikehomologous chromosomes which arejust similar to each other 5. KKaarryyoottyyppeeThe loci provide points along eachchromosome which enable a pair ofchromosomes to align correctlywith each other before separatingduring meiosis 6. In humans: 2n = 46 (diploid) n= 23 (haploid) Fertilization Fusion of the nucleus of ahaploid sperm cell and thenucleus of a haploid eggcell, forming a diploidzygote Zygote Develops into sexuallymature adult with trillions ofcells produced by mitosis. 7. MMEEIIOOSSIISSTwo Meiotic Divisions Meiosis I Homologouschromosomesseparate. Meiosis II Sisterchromatidesareseparated. 8. Syndrome Karyotype Clinical featuresDown Trisomy 21 Short, broad hands with single palmar crease,decreased muscle tone, mentalretardation, broad head with characteristicfeatures, open mouth with large tongue,up-slanting eyes.Turner 45 X Less than 5% survive birth. Female with retardedsexual development, usually sterile, short stature,webbing of skin in neck region, cardiovascularabnormalities, hearing impairment, normalintelligenceEdwards Trisomy 18 Multiple congenital malformations of many organs,low-set malformed ears, recedingmandible, small eyes, mouth and nose withgeneral elfin appearance, severe mentaldeficiency, congenital heart defects, horseshoe ordouble kidney, short sternum,posterior heel prominencePatau Trysomy 13 Severe mental deficiency, small eyes, cleft lipand/or palate, extra fingers and toes,cardiac anomalies, midline brain anomalies,genitourinary abnormalities 9. Syndrome Karyotype Clinical featuresKlinefelter 47, XXY Male, infertile with small testes, may havesome breast development, tall, mild mentaldeficiency, long limbs, at risk for educationalproblemsTriple X 47, XXX Female with normal genitalia and fertility, atrisk for educational and emotionalproblems, early menopausePolyploidy 63 /96chrom.LethalXXY 47, XXY Tall male with normal physical/sexualdevelopment, normal intelligence, increasedtendency for behavioural and psychologicalproblems 10. CCoonncceepptt cchheecckk1. Describe how homologouschromosomes are different from sisterchromatids.2. Compare the number of sets ofchromosomes in human gametes with thenumber of sets in other cells in the body.3. How does meiosis I reduce the numberof chromosomes in the daughter cells?4. What is the final result of meiosis? 11. HOW MEIOSIS INCREASES GENETICVARIATION:Possible # ofcombinations is 2nn= is the haploidnumbern =2 4 combinations n =23 8 million combinations 12. Crossing over alsocontributes togenetic variation.It generatesgeneticrecombinationGenetic recombination isa new combination ofgenetic information in agamete as a result ofcrossing over duringprophase I of meiosis