Each cell has a nucleus- each DNA is located in there. DNA is encoded information for all of our physical features. !!Gregor Mendel 1822-1884- "Father of the Science of Genetics". He discovered how genetic info is passed from generation to generation. !Ideas about inheritance: Mendel had to think out of the box, and look at ◦genetics from a fresh perspective. !2 ideas!‣Blending Theory of Inheritance- the characteristics of the features of •the parents are blended in the offspring!Problems: Children are not always intermediate between their ◦parents. Inbreeding and crossbreeding have been used for thousands of years to make new varieties of animals and plants. !Doctrine of the Fixity-of-Species- each species has a unique and •unchanging set of biological characteristics. Each species was a perfect creation by God. If the species was perfect there was no point for it to change. !Mendel was influenced by:!•Franz Unger- Botanist, did not believe in fixity of species!◦Christian Doppler- Physicist, emphasized measurement and experimentation !◦ !Mendel's Particulate Theory of Inheritance !- Inheritance is due to the passage of discrete particulate factors from one generation to the next in an unchanged form. He crossbreed different organisms (mice) then moved to pea plants. !!Reproduction of plants:!Pollen (sperm)+ Egg= Offspring (seed)!!Advantages of pea plants for genetics!Peas can be cross pollinated or self pollinated. !•Pure bred varieties were available !•Peas make lots of offspring- lots of patterns become available!•!Mendel worked with Pure Breeding Varieties of pea plants each had two different forms of the same trait. (Trait- flower color)!!!!Pure breeding (or true breeding)!always produce progeny of the same type when crossed with themselves or •another individual of the same variety!!He worked with 7 traits. For each trait he had two different forms. 14 in all!Pod shape, Pod color, Flower position, seed shape, seed color, flower color, plant height. !!P1, F1, F2 Generations. !F1 hybrid red flowered plants ------> self fertilized----> F2: 75% Red, 25% White!!Mendel's Law of inheritance (Law of Random Segregation)!To explain his observation each physical trait is coded by 2 factors. They come in different forms.!Each trait is controlled by a pair of factors (genes)!•tall vs dwarf, red vs white, etc!◦One factor is dominant and the other is the recessive !•tall is dominant over dwarf, red over white etc!◦In sexual reproduction the paired factors separate during gamete formation. •Pairs reform in fertilizations !**23,000 genes from mom and dad**!!Mendel's Law!Each trait is controlled by a pair of factors!•!3) during sexual reproduction each parent passes one allele from each gene pair to the offspring. Chance determines which allele is passed. (Here's the Random Segregation)!for each gene pair, we inherit one allele from each parent !◦!!Homozygous- both alleles of a gene pair are the same!Heterozygous- two different alleles!Genotype- genetic makeup!Phenotype- appearance (plant will make red flowers)!Pure breeding Red-flowered parent- Homozygous genotype!!!Punnet Square method !!!!Cystic Fibrosis!-recessive and lethal!- defect in salt movement in and out of cells!most common genetic defect in caucasians !•!Phenylketonuria- recessive!defect in amino acid metabolism!•leads to mental retardation unless a special diet is used!•!Polydactyly- dominant !extra toe or finger!•!Achondroplastic dwarfism-dominant!defect in collagen!•!Marfans Syndrome!dominant!•defect in collagen!•!!!1880's Fertilization: Sperm + Egg & chromosomes discovered!1900: Mendel's work rediscovered !1903: Walter Sutton: chromosomes behave like mendel's factors !The chromosomes carry the genes. the chromosome is found in the nucleus !! everything starts as a single cell= zygote!Sperm + Egg---------------------> zygote!zygote----------------------------> adult! cell division!!!!! exact duplicates!!!Each cell has two copies of each chromosome!!! (4 chromosomes,! 2 pairs)!!2 pairs of HOMOLOGOUS ! chromosomes!!!!homologous chromosomes carry the same genes but may have different alleles!!!!!!!!!different chromosomes (nonhomologous) carry different genes. every chromosomes carry about 1000 genes !!humans have 46 chromosomes- 23 pairs !!!Two types of cell division!Mitosis!•one cell ---------------> two identical daughter cell.!◦Meiosis!•one cell-----------------> four daughter cells each has half as many ◦chromosomes !formation of gametes, one cell divides twice to make 4 cells!◦Division 1: homologous chromosomes are separated !‣Division 2: sister chromatids are separated !‣!!!!Meiosis cuts the chromosome number in half by separating!the homologous chromosomes into separate cells!!Diploid cells: chromosomes in pairs!Haploid cells: no pairs of chromosomes!!!!!!!!!!!!!!!!!!!Fertilization !two haploid cells fuse to make a diploid cell !!!!!!!Chromosomes come in pairs!Cells have two copies of each gene!Members of each pair are homologous- they carry the same genes but may have different alleles!before cell division each chromosome is copied !•sister chromatids are exact duplicates that have the same alleles!•!Q2: the name of the type of cell division that results in the formation of gametes (eggs and sperm) is meiosis !!Sickle-cell anemia- recessive !- due to altered form of Hemoglobin!HbA- allele for normal hemoglobin !HbS- sickle-cell hemoglobin allele!!HbAHbA- normal!!Modifications of Mendell's Law!Partial Dominance or Codominance!•Multiple Alleles!• Partial Dominance/Codominance!neither allele is dominant or recessive!◦heterozygous individuals have a distinct phenotype!◦!Human Familial Hyperchloresterolemia!Genetic defect results in high blood cholesterol levels- can block arteries!normal~100 mg/dL!heterozygous~300mg/dL!fc/fc~700mg/dL!!!Multiple alleles- ABO blood types!A allele- Ia Ia & Ib are codominance!B allele- Ib!O allele- i both Ia and Ib are dominant over
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