Meiosis Also called reduction division . (reduces the amount of DNA by half) Sexual reproduction in that it produces gametes. (sperm, egg, pollen, ovule) Occurs in the ovary or testes, anther or ovule. Produces recombinants. Individuals that are a unique combination of both parents. (gives us genetic variation)
Meiosis I Division occurs just like in mitosis, but with a twist… Crossing over occurs. The cell goes through the cell cycle, but during prophase the homologous chromosomes form tetrads and exchange information where they touch.
Meiosis II Cells undergo mitosis again, except the DNA does not make a copy of itself during interphase. Four daughter cells are produced, each having half the amount of DNA as the original cell.
Diploid vs. Haploid Di ploid cells have 2 sets of chromosomes. (2n) Hap loid cell have 1 set of chromosomes. (n)
Males vs. Females Males produce 4 cells that all participate in reproduction. Females produce one large cell that participates in reproduction, and 3 very small polar bodies.
Organization DNA – RNA – Protein – Gene - Trait
Gregor Mendel The Father of genetics. Using pea plants, he became the first to succeed in predicting how inherited traits are passed on from one generation to the next.
Section 10.1 Summary – pages 253-262 When he wanted to breed, or cross, one plant with another, Mendel opened the petals of a flower and removed the male organs. Remove male parts Mendel chose his subject carefully
Section 10.1 Summary – pages 253-262 He then dusted the female organ with pollen from the plant he wished to cross it with. Female part Transfer pollen Pollen grains Male parts Cross-pollination
Section 10.1 Summary – pages 253-262 The second generation In every case, he found that one trait of a pair seemed to disappear in the F 1 generation, only to reappear unchanged in one-fourth of the F 2 plants.
Section 10.1 Summary – pages 253-262 Mendel called the observed trait dominant and the trait that disappeared recessive . Mendel concluded that the allele for purple plants is dominant to the allele for white plants. The rule of dominance
Section 10.1 Summary – pages 253-262 The rule of dominance An uppercase letter is used for the dominant allele and a lowercase letter for the recessive allele. Ex: Brown eyes – B Blue eyes - b When written together the dominant allele is always written first. Bb T T T T t t t t All tall plants F 1 Tall plant Short plant
P = parental generation F 1 = (Filial) Offspring of the P generation. (children of P) F 2 = Offspring of the F 1 generation. (grandchildren of P)
Trait An inherited characteristic (eye color, hair color…) Organisms have 2 alleles for each trait. (one allele from mom and one from dad)
Section 10.1 Summary – pages 253-262 Phenotypes and Genotypes The physical characteristics of an individual is called its phenotype . (blue eyes, brown hair…) The allele combination for each trait is known as its genotype . (the letters…AA, aa, Aa)
Homozygous Alleles Contains two alleles for the same trait. Represented by AA or aa Also called pure bred
Heterozygous Allele Contains alleles for different traits Represented by A a Also called a hybrid
Types of Crosses Mono hybrid Cross : A cross using one trait. Di hybrid Cross : A cross using two traits.
Law of Independent Assortment Traits assort themselves independently of each other. Ex: Hair color can be inherited separately from eye color.
Punnett Square A method used to determine possible outcomes of a particular cross.
Probability Can be determined by dividing the number of desired outcomes by the total number of possible outcomes. Ex: 2/4 = .50 or 50%
Rules for constructing punnett squares Write out your parental cross. Ex. P = Aa x Aa Derive your alleles. (dihybrids only) Construct and fill in your square. Determine the phenotypic and genotypic ratios